Remove slow assertion (#1592)

[etc/vim.git] / README.md

diff --git a/README.md b/README.md
index 96a24a1eb4ac1d63534ebf8a9cec06d45599a15a..d4b239b7358494f35893774de0f816fc422fbad8 100644 (file)
--- a/README.md
+++ b/README.md
@@ -1,46 +1,45 @@
-![Black Logo](https://raw.githubusercontent.com/ambv/black/master/docs/_static/logo2-readme.png)
+![Black Logo](https://raw.githubusercontent.com/psf/black/master/docs/_static/logo2-readme.png)
+

 <h2 align="center">The Uncompromising Code Formatter</h2>
 
 <p align="center">
 <h2 align="center">The Uncompromising Code Formatter</h2>
 
 <p align="center">

-<a href="https://travis-ci.org/ambv/black"><img alt="Build Status" src="https://travis-ci.org/ambv/black.svg?branch=master"></a>
+<a href="https://travis-ci.com/psf/black"><img alt="Build Status" src="https://travis-ci.com/psf/black.svg?branch=master"></a>
+<a href="https://github.com/psf/black/actions"><img alt="Actions Status" src="https://github.com/psf/black/workflows/Test/badge.svg"></a>
+<a href="https://github.com/psf/black/actions"><img alt="Actions Status" src="https://github.com/psf/black/workflows/Primer/badge.svg"></a>

 <a href="https://black.readthedocs.io/en/stable/?badge=stable"><img alt="Documentation Status" src="https://readthedocs.org/projects/black/badge/?version=stable"></a>
 <a href="https://black.readthedocs.io/en/stable/?badge=stable"><img alt="Documentation Status" src="https://readthedocs.org/projects/black/badge/?version=stable"></a>

-<a href="https://coveralls.io/github/ambv/black?branch=master"><img alt="Coverage Status" src="https://coveralls.io/repos/github/ambv/black/badge.svg?branch=master"></a>
-<a href="https://github.com/ambv/black/blob/master/LICENSE"><img alt="License: MIT" src="https://black.readthedocs.io/en/stable/_static/license.svg"></a>
-<a href="https://pypi.python.org/pypi/black"><img alt="PyPI" src="https://black.readthedocs.io/en/stable/_static/pypi.svg"></a>
-<a href="http://pepy.tech/project/black"><img alt="Downloads" src="http://pepy.tech/badge/black"></a>
-<a href="https://github.com/ambv/black"><img alt="Code style: black" src="https://img.shields.io/badge/code%20style-black-000000.svg"></a>
+<a href="https://coveralls.io/github/psf/black?branch=master"><img alt="Coverage Status" src="https://coveralls.io/repos/github/psf/black/badge.svg?branch=master"></a>
+<a href="https://github.com/psf/black/blob/master/LICENSE"><img alt="License: MIT" src="https://black.readthedocs.io/en/stable/_static/license.svg"></a>
+<a href="https://pypi.org/project/black/"><img alt="PyPI" src="https://img.shields.io/pypi/v/black"></a>
+<a href="https://pepy.tech/project/black"><img alt="Downloads" src="https://pepy.tech/badge/black"></a>
+<a href="https://github.com/psf/black"><img alt="Code style: black" src="https://img.shields.io/badge/code%20style-black-000000.svg"></a>

 </p>
 
 > “Any color you like.”
 
 </p>
 
 > “Any color you like.”
 

+_Black_ is the uncompromising Python code formatter. By using it, you agree to cede
+control over minutiae of hand-formatting. In return, _Black_ gives you speed,
+determinism, and freedom from `pycodestyle` nagging about formatting. You will save time
+and mental energy for more important matters.

 
 

-*Black* is the uncompromising Python code formatter.  By using it, you
-agree to cede control over minutiae of hand-formatting.  In return,
-*Black* gives you speed, determinism, and freedom from `pycodestyle`
-nagging about formatting.  You will save time and mental energy for
-more important matters.
-
-Blackened code looks the same regardless of the project you're reading.
-Formatting becomes transparent after a while and you can focus on the
-content instead.
+Blackened code looks the same regardless of the project you're reading. Formatting
+becomes transparent after a while and you can focus on the content instead.

 
 

-*Black* makes code review faster by producing the smallest diffs
-possible.
+_Black_ makes code review faster by producing the smallest diffs possible.

 
 

-Try it out now using the [Black Playground](https://black.now.sh).
+Try it out now using the [Black Playground](https://black.now.sh). Watch the
+[PyCon 2019 talk](https://youtu.be/esZLCuWs_2Y) to learn more.

 
 ---
 
 
 ---
 

-*Contents:* **[Installation and usage](#installation-and-usage)** |
-**[Code style](#the-black-code-style)** |
-**[pyproject.toml](#pyprojecttoml)** |
-**[Editor integration](#editor-integration)** |
+_Contents:_ **[Installation and usage](#installation-and-usage)** |
+**[Code style](#the-black-code-style)** | **[Pragmatism](#pragmatism)** |
+**[pyproject.toml](#pyprojecttoml)** | **[Editor integration](#editor-integration)** |
+**[blackd](#blackd)** | **[black-primer](#black-primer)** |

 **[Version control integration](#version-control-integration)** |
 **[Version control integration](#version-control-integration)** |

-**[Ignoring unmodified files](#ignoring-unmodified-files)** |
-**[Testimonials](#testimonials)** |
-**[Show your style](#show-your-style)** |
-**[Contributing](#contributing-to-black)** |
-**[Change Log](#change-log)** |
+**[GitHub Actions](#github-actions)** |
+**[Ignoring unmodified files](#ignoring-unmodified-files)** | **[Used by](#used-by)** |
+**[Testimonials](#testimonials)** | **[Show your style](#show-your-style)** |
+**[Contributing](#contributing-to-black)** | **[Change log](#change-log)** |

 **[Authors](#authors)**
 
 ---
 **[Authors](#authors)**
 
 ---


@@ -49,499 +48,249 @@ Try it out now using the [Black Playground](https://black.now.sh).
 
 ### Installation
 
 
 ### Installation
 

-*Black* can be installed by running `pip install black`.  It requires
-Python 3.6.0+ to run but you can reformat Python 2 code with it, too.
+_Black_ can be installed by running `pip install black`. It requires Python 3.6.0+ to
+run but you can reformat Python 2 code with it, too.
+
+#### Install from GitHub

 
 

+If you can't wait for the latest _hotness_ and want to install from GitHub, use:
+
+`pip install git+git://github.com/psf/black`

 
 ### Usage
 
 To get started right away with sensible defaults:
 
 
 ### Usage
 
 To get started right away with sensible defaults:
 

-```
+```sh

 black {source_file_or_directory}
 ```
 
 black {source_file_or_directory}
 ```
 

-### Command line options
-
-*Black* doesn't provide many options.  You can list them by running
-`black --help`:
-
-```text
-black [OPTIONS] [SRC]...
+You can run _Black_ as a package if running it as a script doesn't work:

 
 

-Options:
-  -l, --line-length INTEGER   Where to wrap around.  [default: 88]
-  --py36                      Allow using Python 3.6-only syntax on all input
-                              files.  This will put trailing commas in function
-                              signatures and calls also after *args and
-                              **kwargs.  [default: per-file auto-detection]
-  --pyi                       Format all input files like typing stubs
-                              regardless of file extension (useful when piping
-                              source on standard input).
-  -S, --skip-string-normalization
-                              Don't normalize string quotes or prefixes.
-  --check                     Don't write the files back, just return the
-                              status.  Return code 0 means nothing would
-                              change.  Return code 1 means some files would be
-                              reformatted.  Return code 123 means there was an
-                              internal error.
-  --diff                      Don't write the files back, just output a diff
-                              for each file on stdout.
-  --fast / --safe             If --fast given, skip temporary sanity checks.
-                              [default: --safe]
-  --include TEXT              A regular expression that matches files and
-                              directories that should be included on
-                              recursive searches. On Windows, use forward
-                              slashes for directories.  [default: \.pyi?$]
-  --exclude TEXT              A regular expression that matches files and
-                              directories that should be excluded on
-                              recursive searches. On Windows, use forward
-                              slashes for directories.  [default:
-                              build/|buck-out/|dist/|_build/|\.git/|\.hg/|
-                              \.mypy_cache/|\.tox/|\.venv/]
-  -q, --quiet                 Don't emit non-error messages to stderr. Errors
-                              are still emitted, silence those with
-                              2>/dev/null.
-  -v, --verbose               Also emit messages to stderr about files
-                              that were not changed or were ignored due to
-                              --exclude=.
-  --version                   Show the version and exit.
-  --config PATH               Read configuration from PATH.
-  --help                      Show this message and exit.
+```sh
+python -m black {source_file_or_directory}

 ```
 
 ```
 

-*Black* is a well-behaved Unix-style command-line tool:
-* it does nothing if no sources are passed to it;
-* it will read from standard input and write to standard output if `-`
-  is used as the filename;
-* it only outputs messages to users on standard error;
-* exits with code 0 unless an internal error occurred (or `--check` was
-  used).
-
-
-### NOTE: This is a beta product
+### Command line options

 
 

-*Black* is already successfully used by several projects, small and big.
-It also sports a decent test suite.  However, it is still very new.
-Things will probably be wonky for a while. This is made explicit by the
-"Beta" trove classifier, as well as by the "b" in the version number.
-What this means for you is that **until the formatter becomes stable,
-you should expect some formatting to change in the future**.  That being
-said, no drastic stylistic changes are planned, mostly responses to bug
-reports.
+_Black_ doesn't provide many options. You can list them by running `black --help`:

 
 

-Also, as a temporary safety measure, *Black* will check that the
-reformatted code still produces a valid AST that is equivalent to the
-original.  This slows it down.  If you're feeling confident, use
-``--fast``.
+```text
+Usage: black [OPTIONS] [SRC]...

 
 

+  The uncompromising code formatter.

 
 

-## The *Black* code style
+Options:
+  -c, --code TEXT                 Format the code passed in as a string.
+  -l, --line-length INTEGER       How many characters per line to allow.
+                                  [default: 88]

 
 

-*Black* reformats entire files in place.  It is not configurable.  It
-doesn't take previous formatting into account.  It doesn't reformat
-blocks that start with `# fmt: off` and end with `# fmt: on`.  It also
-recognizes [YAPF](https://github.com/google/yapf)'s block comments to
-the same effect, as a courtesy for straddling code.
+  -t, --target-version [py27|py33|py34|py35|py36|py37|py38]
+                                  Python versions that should be supported by
+                                  Black's output. [default: per-file auto-
+                                  detection]

 
 

+  --pyi                           Format all input files like typing stubs
+                                  regardless of file extension (useful when
+                                  piping source on standard input).

 
 

-### How *Black* wraps lines
+  -S, --skip-string-normalization
+                                  Don't normalize string quotes or prefixes.
+  --check                         Don't write the files back, just return the
+                                  status.  Return code 0 means nothing would
+                                  change.  Return code 1 means some files
+                                  would be reformatted. Return code 123 means
+                                  there was an internal error.
+
+  --diff                          Don't write the files back, just output a
+                                  diff for each file on stdout.
+
+  --color / --no-color            Show colored diff. Only applies when
+                                  `--diff` is given.
+
+  --fast / --safe                 If --fast given, skip temporary sanity
+                                  checks. [default: --safe]
+
+  --include TEXT                  A regular expression that matches files and
+                                  directories that should be included on
+                                  recursive searches.  An empty value means
+                                  all files are included regardless of the
+                                  name.  Use forward slashes for directories
+                                  on all platforms (Windows, too).  Exclusions
+                                  are calculated first, inclusions later.
+                                  [default: \.pyi?$]
+
+  --exclude TEXT                  A regular expression that matches files and
+                                  directories that should be excluded on
+                                  recursive searches.  An empty value means no
+                                  paths are excluded. Use forward slashes for
+                                  directories on all platforms (Windows, too).
+                                  Exclusions are calculated first, inclusions
+                                  later.  [default: /(\.eggs|\.git|\.hg|\.mypy
+                                  _cache|\.nox|\.tox|\.venv|\.svn|_build|buck-
+                                  out|build|dist)/]
+
+  --force-exclude TEXT            Like --exclude, but files and directories
+                                  matching this regex will be excluded even
+                                  when they are passed explicitly as arguments
+
+  -q, --quiet                     Don't emit non-error messages to stderr.
+                                  Errors are still emitted; silence those with
+                                  2>/dev/null.
+
+  -v, --verbose                   Also emit messages to stderr about files
+                                  that were not changed or were ignored due to
+                                  --exclude=.
+
+  --version                       Show the version and exit.
+  --config FILE                   Read configuration from FILE path.
+  -h, --help                      Show this message and exit.
+```

 
 

-*Black* ignores previous formatting and applies uniform horizontal
-and vertical whitespace to your code.  The rules for horizontal
-whitespace can be summarized as: do whatever makes `pycodestyle` happy.
-The coding style used by *Black* can be viewed as a strict subset of
-PEP 8.
+_Black_ is a well-behaved Unix-style command-line tool:

 
 

-As for vertical whitespace, *Black* tries to render one full expression
-or simple statement per line.  If this fits the allotted line length,
-great.
-```py3
-# in:
+- it does nothing if no sources are passed to it;
+- it will read from standard input and write to standard output if `-` is used as the
+  filename;
+- it only outputs messages to users on standard error;
+- exits with code 0 unless an internal error occurred (or `--check` was used).

 
 

-l = [1,
-     2,
-     3,
-]
+### Using _Black_ with other tools

 
 

-# out:
+While _Black_ enforces formatting that conforms to PEP 8, other tools may raise warnings
+about _Black_'s changes or will overwrite _Black_'s changes. A good example of this is
+[isort](https://pypi.org/p/isort). Since _Black_ is barely configurable, these tools
+should be configured to neither warn about nor overwrite _Black_'s changes.

 
 

-l = [1, 2, 3]
-```
+Actual details on _Black_ compatible configurations for various tools can be found in
+[compatible_configs](https://github.com/psf/black/blob/master/docs/compatible_configs.md).

 
 

-If not, *Black* will look at the contents of the first outer matching
-brackets and put that in a separate indented line.
-```py3
-# in:
+### Migrating your code style without ruining git blame

 
 

-TracebackException.from_exception(exc, limit, lookup_lines, capture_locals)
+A long-standing argument against moving to automated code formatters like _Black_ is
+that the migration will clutter up the output of `git blame`. This was a valid argument,
+but since Git version 2.23, Git natively supports
+[ignoring revisions in blame](https://git-scm.com/docs/git-blame#Documentation/git-blame.txt---ignore-revltrevgt)
+with the `--ignore-rev` option. You can also pass a file listing the revisions to ignore
+using the `--ignore-revs-file` option. The changes made by the revision will be ignored
+when assigning blame. Lines modified by an ignored revision will be blamed on the
+previous revision that modified those lines.

 
 

-# out:
+So when migrating your project's code style to _Black_, reformat everything and commit
+the changes (preferably in one massive commit). Then put the full 40 characters commit
+identifier(s) into a file.

 
 

-TracebackException.from_exception(
-    exc, limit, lookup_lines, capture_locals
-)

 ```
 ```

-
-If that still doesn't fit the bill, it will decompose the internal
-expression further using the same rule, indenting matching brackets
-every time.  If the contents of the matching brackets pair are
-comma-separated (like an argument list, or a dict literal, and so on)
-then *Black* will first try to keep them on the same line with the
-matching brackets.  If that doesn't work, it will put all of them in
-separate lines.
-```py3
-# in:
-
-def very_important_function(template: str, *variables, file: os.PathLike, debug: bool = False):
-    """Applies `variables` to the `template` and writes to `file`."""
-    with open(file, 'w') as f:
-        ...
-
-# out:
-
-def very_important_function(
-    template: str,
-    *variables,
-    file: os.PathLike,
-    debug: bool = False,
-):
-    """Applies `variables` to the `template` and writes to `file`."""
-    with open(file, "w") as f:
-        ...
+# Migrate code style to Black
+5b4ab991dede475d393e9d69ec388fd6bd949699

 ```
 
 ```
 

-You might have noticed that closing brackets are always dedented and
-that a trailing comma is always added.  Such formatting produces smaller
-diffs; when you add or remove an element, it's always just one line.
-Also, having the closing bracket dedented provides a clear delimiter
-between two distinct sections of the code that otherwise share the same
-indentation level (like the arguments list and the docstring in the
-example above).
-
-If a data structure literal (tuple, list, set, dict) or a line of "from"
-imports cannot fit in the allotted length, it's always split into one
-element per line.  This minimizes diffs as well as enables readers of
-code to find which commit introduced a particular entry.  This also
-makes *Black* compatible with [isort](https://pypi.org/p/isort/) with
-the following configuration.
+Afterwards, you can pass that file to `git blame` and see clean and meaningful blame
+information.

 
 

-<details>
-<summary>A compatible `.isort.cfg`</summary>
-
-```
-[settings]
-multi_line_output=3
-include_trailing_comma=True
-force_grid_wrap=0
-combine_as_imports=True
-line_length=88
+```console
+$ git blame important.py --ignore-revs-file .git-blame-ignore-revs
+7a1ae265 (John Smith 2019-04-15 15:55:13 -0400 1) def very_important_function(text, file):
+abdfd8b0 (Alice Doe  2019-09-23 11:39:32 -0400 2)     text = text.lstrip()
+7a1ae265 (John Smith 2019-04-15 15:55:13 -0400 3)     with open(file, "r+") as f:
+7a1ae265 (John Smith 2019-04-15 15:55:13 -0400 4)         f.write(formatted)

 ```
 
 ```
 

-The equivalent command line is:
-```
-$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --combine-as --line-width=88 [ file.py ]
-```
-</details>
+You can even configure `git` to automatically ignore revisions listed in a file on every
+call to `git blame`.

 
 

-### Line length
-
-You probably noticed the peculiar default line length.  *Black* defaults
-to 88 characters per line, which happens to be 10% over 80.  This number
-was found to produce significantly shorter files than sticking with 80
-(the most popular), or even 79 (used by the standard library).  In
-general, [90-ish seems like the wise choice](https://youtu.be/wf-BqAjZb8M?t=260).
-
-If you're paid by the line of code you write, you can pass
-`--line-length` with a lower number.  *Black* will try to respect that.
-However, sometimes it won't be able to without breaking other rules.  In
-those rare cases, auto-formatted code will exceed your allotted limit.
-
-You can also increase it, but remember that people with sight disabilities
-find it harder to work with line lengths exceeding 100 characters.
-It also adversely affects side-by-side diff review  on typical screen
-resolutions.  Long lines also make it harder to present code neatly
-in documentation or talk slides.
-
-If you're using Flake8, you can bump `max-line-length` to 88 and forget
-about it.  Alternatively, use [Bugbear](https://github.com/PyCQA/flake8-bugbear)'s
-B950 warning instead of E501 and keep the max line length at 80 which
-you are probably already using.  You'd do it like this:
-```ini
-[flake8]
-max-line-length = 80
-...
-select = C,E,F,W,B,B950
-ignore = E501
+```console
+$ git config blame.ignoreRevsFile .git-blame-ignore-revs

 ```
 
 ```
 

-You'll find *Black*'s own .flake8 config file is configured like this.
-If you're curious about the reasoning behind B950, Bugbear's documentation
-explains it.  The tl;dr is "it's like highway speed limits, we won't
-bother you if you overdo it by a few km/h".
-
-
-### Empty lines
-
-*Black* avoids spurious vertical whitespace.  This is in the spirit of
-PEP 8 which says that in-function vertical whitespace should only be
-used sparingly.
-
-*Black* will allow single empty lines inside functions, and single and
-double empty lines on module level left by the original editors, except
-when they're within parenthesized expressions.  Since such expressions
-are always reformatted to fit minimal space, this whitespace is lost.
-
-It will also insert proper spacing before and after function definitions.
-It's one line before and after inner functions and two lines before and
-after module-level functions and classes.  *Black* will not put empty
-lines between function/class definitions and standalone comments that
-immediately precede the given function/class.
+**The one caveat is that GitHub and GitLab do not yet support ignoring revisions using
+their native UI of blame.** So blame information will be cluttered with a reformatting
+commit on those platforms. (If you'd like this feature, there's an open issue for
+[GitLab](https://gitlab.com/gitlab-org/gitlab/-/issues/31423) and please let GitHub
+know!)

 
 

-*Black* will enforce single empty lines between a class-level docstring
-and the first following field or method.  This conforms to
-[PEP 257](https://www.python.org/dev/peps/pep-0257/#multi-line-docstrings).
-
-*Black* won't insert empty lines after function docstrings unless that
-empty line is required due to an inner function starting immediately
-after.
+### NOTE: This is a beta product

 
 

+_Black_ is already [successfully used](#used-by) by many projects, small and big. It
+also sports a decent test suite. However, it is still very new. Things will probably be
+wonky for a while. This is made explicit by the "Beta" trove classifier, as well as by
+the "b" in the version number. What this means for you is that **until the formatter
+becomes stable, you should expect some formatting to change in the future**. That being
+said, no drastic stylistic changes are planned, mostly responses to bug reports.

 
 

-### Trailing commas
+Also, as a temporary safety measure, _Black_ will check that the reformatted code still
+produces a valid AST that is equivalent to the original. This slows it down. If you're
+feeling confident, use `--fast`.

 
 

-*Black* will add trailing commas to expressions that are split
-by comma where each element is on its own line.  This includes function
-signatures.
+## The _Black_ code style

 
 

-Unnecessary trailing commas are removed if an expression fits in one
-line.  This makes it 1% more likely that your line won't exceed the
-allotted line length limit.  Moreover, in this scenario, if you added
-another argument to your call, you'd probably fit it in the same line
-anyway.  That doesn't make diffs any larger.
-
-One exception to removing trailing commas is tuple expressions with
-just one element.  In this case *Black* won't touch the single trailing
-comma as this would unexpectedly change the underlying data type.  Note
-that this is also the case when commas are used while indexing.  This is
-a tuple in disguise: ```numpy_array[3, ]```.
-
-One exception to adding trailing commas is function signatures
-containing `*`, `*args`, or `**kwargs`.  In this case a trailing comma
-is only safe to use on Python 3.6.  *Black* will detect if your file is
-already 3.6+ only and use trailing commas in this situation.  If you
-wonder how it knows, it looks for f-strings and existing use of trailing
-commas in function signatures that have stars in them.  In other words,
-if you'd like a trailing comma in this situation and *Black* didn't
-recognize it was safe to do so, put it there manually and *Black* will
-keep it.
-
-
-### Strings
-
-*Black* prefers double quotes (`"` and `"""`) over single quotes (`'`
-and `'''`).  It will replace the latter with the former as long as it
-does not result in more backslash escapes than before.
-
-*Black* also standardizes string prefixes, making them always lowercase.
-On top of that, if your code is already Python 3.6+ only or it's using
-the `unicode_literals` future import, *Black* will remove `u` from the
-string prefix as it is meaningless in those scenarios.
-
-The main reason to standardize on a single form of quotes is aesthetics.
-Having one kind of quotes everywhere reduces reader distraction.
-It will also enable a future version of *Black* to merge consecutive
-string literals that ended up on the same line (see
-[#26](https://github.com/ambv/black/issues/26) for details).
-
-Why settle on double quotes?  They anticipate apostrophes in English
-text.  They match the docstring standard described in PEP 257.  An
-empty string in double quotes (`""`) is impossible to confuse with
-a one double-quote regardless of fonts and syntax highlighting used.
-On top of this, double quotes for strings are consistent with C which
-Python interacts a lot with.
-
-On certain keyboard layouts like US English, typing single quotes is
-a bit easier than double quotes.  The latter requires use of the Shift
-key.  My recommendation here is to keep using whatever is faster to type
-and let *Black* handle the transformation.
-
-If you are adopting *Black* in a large project with pre-existing string
-conventions (like the popular ["single quotes for data, double quotes for
-human-readable strings"](https://stackoverflow.com/a/56190)), you can
-pass `--skip-string-normalization` on the command line.  This is meant as
-an adoption helper, avoid using this for new projects.
-
-
-### Line breaks & binary operators
-
-*Black* will break a line before a binary operator when splitting a block
-of code over multiple lines. This is so that *Black* is compliant with the
-recent changes in the [PEP 8](https://www.python.org/dev/peps/pep-0008/#should-a-line-break-before-or-after-a-binary-operator)
-style guide, which emphasizes that this approach improves readability.
-
-This behaviour may raise ``W503 line break before binary operator`` warnings in
-style guide enforcement tools like Flake8. Since ``W503`` is not PEP 8 compliant,
-you should tell Flake8 to ignore these warnings.
-
-
-### Slices
-
-PEP 8 [recommends](https://www.python.org/dev/peps/pep-0008/#whitespace-in-expressions-and-statements)
-to treat ``:`` in slices as a binary operator with the lowest priority, and to
-leave an equal amount of space on either side, except if a parameter is omitted
-(e.g. ``ham[1 + 1 :]``). It also states that for extended slices, both ``:``
-operators have to have the same amount of spacing, except if a parameter is
-omitted (``ham[1 + 1 ::]``). *Black* enforces these rules consistently.
-
-This behaviour may raise ``E203 whitespace before ':'`` warnings in style guide
-enforcement tools like Flake8. Since ``E203`` is not PEP 8 compliant, you should
-tell Flake8 to ignore these warnings.
-
-
-### Parentheses
-
-Some parentheses are optional in the Python grammar.  Any expression can
-be wrapped in a pair of parentheses to form an atom.  There are a few
-interesting cases:
-
-- `if (...):`
-- `while (...):`
-- `for (...) in (...):`
-- `assert (...), (...)`
-- `from X import (...)`
-- assignments like:
-  - `target = (...)`
-  - `target: type = (...)`
-  - `some, *un, packing = (...)`
-  - `augmented += (...)`
-
-In those cases, parentheses are removed when the entire statement fits
-in one line, or if the inner expression doesn't have any delimiters to
-further split on.  If there is only a single delimiter and the expression
-starts or ends with a bracket, the parenthesis can also be successfully
-omitted since the existing bracket pair will organize the expression
-neatly anyway.  Otherwise, the parentheses are added.
-
-Please note that *Black* does not add or remove any additional nested
-parentheses that you might want to have for clarity or further
-code organization.  For example those parentheses are not going to be
-removed:
-```py3
-return not (this or that)
-decision = (maybe.this() and values > 0) or (maybe.that() and values < 0)
-```
+_Black_ is a PEP 8 compliant opinionated formatter. _Black_ reformats entire files in
+place. It is not configurable. It doesn't take previous formatting into account. Your
+main option of configuring _Black_ is that it doesn't reformat blocks that start with
+`# fmt: off` and end with `# fmt: on`. `# fmt: on/off` have to be on the same level of
+indentation. To learn more about _Black_'s opinions, to go
+[the_black_code_style](https://github.com/psf/black/blob/master/docs/the_black_code_style.md).

 
 

+Please refer to this document before submitting an issue. What seems like a bug might be
+intended behaviour.

 
 

-### Call chains
-
-Some popular APIs, like ORMs, use call chaining.  This API style is known
-as a [fluent interface](https://en.wikipedia.org/wiki/Fluent_interface).
-*Black* formats those by treating dots that follow a call or an indexing
-operation like a very low priority delimiter.  It's easier to show the
-behavior than to explain it.  Look at the example:
-```py3
-def example(session):
-    result = (
-        session.query(models.Customer.id)
-        .filter(
-            models.Customer.account_id == account_id,
-            models.Customer.email == email_address,
-        )
-        .order_by(models.Customer.id.asc())
-        .all()
-    )
-```
-
+## Pragmatism

 
 

-### Typing stub files
-
-PEP 484 describes the syntax for type hints in Python.  One of the
-use cases for typing is providing type annotations for modules which
-cannot contain them directly (they might be written in C, or they might
-be third-party, or their implementation may be overly dynamic, and so on).
-
-To solve this, [stub files with the `.pyi` file
-extension](https://www.python.org/dev/peps/pep-0484/#stub-files) can be
-used to describe typing information for an external module.  Those stub
-files omit the implementation of classes and functions they
-describe, instead they only contain the structure of the file (listing
-globals, functions, and classes with their members).  The recommended
-code style for those files is more terse than PEP 8:
-
-* prefer `...` on the same line as the class/function signature;
-* avoid vertical whitespace between consecutive module-level functions,
-  names, or methods and fields within a single class;
-* use a single blank line between top-level class definitions, or none
-  if the classes are very small.
-
-*Black* enforces the above rules.  There are additional guidelines for
-formatting `.pyi` file that are not enforced yet but might be in
-a future version of the formatter:
-
-* all function bodies should be empty (contain `...` instead of the body);
-* do not use docstrings;
-* prefer `...` over `pass`;
-* for arguments with a default, use `...` instead of the actual default;
-* avoid using string literals in type annotations, stub files support
-  forward references natively (like Python 3.7 code with `from __future__
-  import annotations`);
-* use variable annotations instead of type comments, even for stubs that
-  target older versions of Python;
-* for arguments that default to `None`, use `Optional[]` explicitly;
-* use `float` instead of `Union[int, float]`.
+Early versions of _Black_ used to be absolutist in some respects. They took after its
+initial author. This was fine at the time as it made the implementation simpler and
+there were not many users anyway. Not many edge cases were reported. As a mature tool,
+_Black_ does make some exceptions to rules it otherwise holds. This
+[section](https://github.com/psf/black/blob/master/docs/the_black_code_style.md#pragmatism)
+of `the_black_code_style` describes what those exceptions are and why this is the case.

 
 

+Please refer to this document before submitting an issue just like with the document
+above. What seems like a bug might be intended behaviour.

 
 ## pyproject.toml
 
 
 ## pyproject.toml
 

-*Black* is able to read project-specific default values for its
-command line options from a `pyproject.toml` file.  This is
-especially useful for specifying custom `--include` and `--exclude`
-patterns for your project.
-
-**Pro-tip**: If you're asking yourself "Do I need to configure anything?"
-the answer is "No".  *Black* is all about sensible defaults.
+_Black_ is able to read project-specific default values for its command line options
+from a `pyproject.toml` file. This is especially useful for specifying custom
+`--include` and `--exclude` patterns for your project.

 
 

+**Pro-tip**: If you're asking yourself "Do I need to configure anything?" the answer is
+"No". _Black_ is all about sensible defaults.

 
 ### What on Earth is a `pyproject.toml` file?
 
 
 ### What on Earth is a `pyproject.toml` file?
 

-[PEP 518](https://www.python.org/dev/peps/pep-0518/) defines
-`pyproject.toml` as a configuration file to store build system
-requirements for Python projects.  With the help of tools
-like [Poetry](https://poetry.eustace.io/) or
-[Flit](https://flit.readthedocs.io/en/latest/) it can fully replace the
-need for `setup.py` and `setup.cfg` files.
-
+[PEP 518](https://www.python.org/dev/peps/pep-0518/) defines `pyproject.toml` as a
+configuration file to store build system requirements for Python projects. With the help
+of tools like [Poetry](https://python-poetry.org/) or
+[Flit](https://flit.readthedocs.io/en/latest/) it can fully replace the need for
+`setup.py` and `setup.cfg` files.

 
 

-### Where *Black* looks for the file
+### Where _Black_ looks for the file

 
 

-By default *Black* looks for `pyproject.toml` starting from the common
-base directory of all files and directories passed on the command line.
-If it's not there, it looks in parent directories.  It stops looking
-when it finds the file, or a `.git` directory, or a `.hg` directory,
-or the root of the file system, whichever comes first.
+By default _Black_ looks for `pyproject.toml` starting from the common base directory of
+all files and directories passed on the command line. If it's not there, it looks in
+parent directories. It stops looking when it finds the file, or a `.git` directory, or a
+`.hg` directory, or the root of the file system, whichever comes first.

 
 

-If you're formatting standard input, *Black* will look for configuration
-starting from the current working directory.
+If you're formatting standard input, _Black_ will look for configuration starting from
+the current working directory.

 
 

-You can also explicitly specify the path to a particular file that you
-want with `--config`.  In this situation *Black* will not look for any
-other file.
+You can also explicitly specify the path to a particular file that you want with
+`--config`. In this situation _Black_ will not look for any other file.

 
 

-If you're running with `--verbose`, you will see a blue message if
-a file was found and used.
+If you're running with `--verbose`, you will see a blue message if a file was found and
+used.

 
 

+Please note `blackd` will not use `pyproject.toml` configuration.

 
 ### Configuration format
 
 
 ### Configuration format
 

-As the file extension suggests, `pyproject.toml` is a [TOML](https://github.com/toml-lang/toml) file.  It contains separate
-sections for different tools.  *Black* is using the `[tool.black]`
-section.  The option keys are the same as long names of options on
-the command line.
+As the file extension suggests, `pyproject.toml` is a
+[TOML](https://github.com/toml-lang/toml) file. It contains separate sections for
+different tools. _Black_ is using the `[tool.black]` section. The option keys are the
+same as long names of options on the command line.

 
 

-Note that you have to use single-quoted strings in TOML for regular
-expressions. It's the equivalent of r-strings in Python.  Multiline
-strings are treated as verbose regular expressions by Black.  Use `[ ]`
-to denote a significant space character.
+Note that you have to use single-quoted strings in TOML for regular expressions. It's
+the equivalent of r-strings in Python. Multiline strings are treated as verbose regular
+expressions by Black. Use `[ ]` to denote a significant space character.

 
 <details>
 <summary>Example `pyproject.toml`</summary>
 
 <details>
 <summary>Example `pyproject.toml`</summary>


@@ -549,24 +298,26 @@ to denote a significant space character.
 ```toml
 [tool.black]
 line-length = 88
 ```toml
 [tool.black]
 line-length = 88

-py36 = true
+target-version = ['py37']

 include = '\.pyi?$'
 exclude = '''
 include = '\.pyi?$'
 exclude = '''

-/(
-    \.git
-  | \.hg
-  | \.mypy_cache
-  | \.tox
-  | \.venv
-  | _build
-  | buck-out
-  | build
-  | dist
-
-  # The following are specific to Black, you probably don't want those.
-  | blib2to3
-  | tests/data
-)/
+
+(
+  /(
+      \.eggs         # exclude a few common directories in the
+    | \.git          # root of the project
+    | \.hg
+    | \.mypy_cache
+    | \.tox
+    | \.venv
+    | _build
+    | buck-out
+    | build
+    | dist
+  )/
+  | foo.py           # also separately exclude a file named foo.py in
+                     # the root of the project
+)

 '''
 ```
 
 '''
 ```
 


@@ -574,220 +325,129 @@ exclude = '''
 
 ### Lookup hierarchy
 
 
 ### Lookup hierarchy
 

-Command-line options have defaults that you can see in `--help`.
-A `pyproject.toml` can override those defaults.  Finally, options
-provided by the user on the command line override both.
-
-*Black* will only ever use one `pyproject.toml` file during an entire
-run. It doesn't look for multiple files, and doesn't compose
-configuration from different levels of the file hierarchy.
+Command-line options have defaults that you can see in `--help`. A `pyproject.toml` can
+override those defaults. Finally, options provided by the user on the command line
+override both.

 
 

+_Black_ will only ever use one `pyproject.toml` file during an entire run. It doesn't
+look for multiple files, and doesn't compose configuration from different levels of the
+file hierarchy.

 
 ## Editor integration
 
 
 ## Editor integration
 

-### Emacs
-
-Use [proofit404/blacken](https://github.com/proofit404/blacken).
-
-
-### PyCharm
-
-1. Install `black`.
-
-```console
-$ pip install black
-```
-
-2. Locate your `black` installation folder.
-
-  On macOS / Linux / BSD:
-
-```console
-$ which black
-/usr/local/bin/black  # possible location
-```
-
-  On Windows:
-
-```console
-$ where black
-%LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe  # possible location
-```
+_Black_ can be integrated into many editors with plugins. They let you run _Black_ on
+your code with the ease of doing it in your editor. To get started using _Black_ in your
+editor of choice, please see
+[editor_integration](https://github.com/psf/black/blob/master/docs/editor_integration.md).

 
 

-3. Open External tools in PyCharm with `File -> Settings -> Tools -> External Tools`.
+Patches are welcome for editors without an editor integration or plugin! More
+information can be found in
+[editor_integration](https://github.com/psf/black/blob/master/docs/editor_integration.md#other-editors).

 
 

-4. Click the + icon to add a new external tool with the following values:
-    - Name: Black
-    - Description: Black is the uncompromising Python code formatter.
-    - Program: <install_location_from_step_2>
-    - Arguments: `$FilePath$`
+## blackd

 
 

-5. Format the currently opened file by selecting `Tools -> External Tools -> black`.
-    - Alternatively, you can set a keyboard shortcut by navigating to `Preferences -> Keymap -> External Tools -> External Tools - Black`.
+`blackd` is a small HTTP server that exposes Black's functionality over a simple
+protocol. The main benefit of using it is to avoid paying the cost of starting up a new
+Black process every time you want to blacken a file. Please refer to
+[blackd](https://github.com/psf/black/blob/master/docs/blackd.md) to get the ball
+rolling.

 
 

-6. Optionally, run Black on every file save:
+## black-primer

 
 

-    1. Make sure you have the [File Watcher](https://plugins.jetbrains.com/plugin/7177-file-watchers) plugin installed.
-    2. Go to `Preferences -> Tools -> File Watchers` and click `+` to add a new watcher:
-        - Name: Black
-        - File type: Python
-        - Scope: Project Files
-        - Program: <install_location_from_step_2>
-        - Arguments: `$FilePath$`
-        - Output paths to refresh: `$FilePathRelativeToProjectRoot$`
-        - Working directory: `$ProjectFileDir$`
-
-### Vim
-
-Commands and shortcuts:
-
-* `:Black` to format the entire file (ranges not supported);
-* `:BlackUpgrade` to upgrade *Black* inside the virtualenv;
-* `:BlackVersion` to get the current version of *Black* inside the
-  virtualenv.
-
-Configuration:
-* `g:black_fast` (defaults to `0`)
-* `g:black_linelength` (defaults to `88`)
-* `g:black_skip_string_normalization` (defaults to `0`)
-* `g:black_virtualenv` (defaults to `~/.vim/black`)
-
-To install with [vim-plug](https://github.com/junegunn/vim-plug):
-
-```
-Plug 'ambv/black',
-```
+`black-primer` is a tool built for CI (and humans) to have _Black_ `--check` a number of
+(configured in `primer.json`) Git accessible projects in parallel.
+[black_primer](https://github.com/psf/black/blob/master/docs/black_primer.md) has more
+information regarding its usage and configuration.

 
 

-or with [Vundle](https://github.com/VundleVim/Vundle.vim):
+(A PR adding Mercurial support will be accepted.)

 
 

-```
-Plugin 'ambv/black'
-```
-
-or you can copy the plugin from [plugin/black.vim](https://github.com/ambv/black/tree/master/plugin/black.vim).
-Let me know if this requires any changes to work with Vim 8's builtin
-`packadd`, or Pathogen, and so on.
-
-This plugin **requires Vim 7.0+ built with Python 3.6+ support**.  It
-needs Python 3.6 to be able to run *Black* inside the Vim process which
-is much faster than calling an external command.
-
-On first run, the plugin creates its own virtualenv using the right
-Python version and automatically installs *Black*. You can upgrade it later
-by calling `:BlackUpgrade` and restarting Vim.
-
-If you need to do anything special to make your virtualenv work and
-install *Black* (for example you want to run a version from master),
-create a virtualenv manually and point `g:black_virtualenv` to it.
-The plugin will use it.
+## Version control integration

 
 

-To run *Black* on save, add the following line to `.vimrc` or `init.vim`:
+Use [pre-commit](https://pre-commit.com/). Once you
+[have it installed](https://pre-commit.com/#install), add this to the
+`.pre-commit-config.yaml` in your repository:

 
 

+```yaml
+repos:
+  - repo: https://github.com/psf/black
+    rev: 19.10b0 # Replace by any tag/version: https://github.com/psf/black/tags
+    hooks:
+      - id: black
+        language_version: python3 # Should be a command that runs python3.6+

 ```
 ```

-autocmd BufWritePre *.py execute ':Black'
-```
-
-**How to get Vim with Python 3.6?**
-On Ubuntu 17.10 Vim comes with Python 3.6 by default.
-On macOS with Homebrew run: `brew install vim --with-python3`.
-When building Vim from source, use:
-`./configure --enable-python3interp=yes`. There's many guides online how
-to do this.
-
-
-### Visual Studio Code
-
-Use the [Python extension](https://marketplace.visualstudio.com/items?itemName=ms-python.python)
-([instructions](https://code.visualstudio.com/docs/python/editing#_formatting)).
-

 
 

-### SublimeText 3
-
-Use [sublack plugin](https://github.com/jgirardet/sublack).
-
-
-### IPython Notebook Magic
-
-Use [blackcellmagic](https://github.com/csurfer/blackcellmagic).
-
-
-### Python Language Server
-
-If your editor supports the [Language Server Protocol](https://langserver.org/)
-(Atom, Sublime Text, Visual Studio Code and many more), you can use
-the [Python Language Server](https://github.com/palantir/python-language-server) with the
-[pyls-black](https://github.com/rupert/pyls-black) plugin.
-
-
-### Atom/Nuclide
-
-Use [atom-black](https://github.com/hauntsaninja/atom-black).
-
-
-### Other editors
-
-Other editors will require external contributions.
-
-Patches welcome! ✨ 🍰 ✨
+Then run `pre-commit install` and you're ready to go.

 
 

-Any tool that can pipe code through *Black* using its stdio mode (just
-[use `-` as the file name](https://www.tldp.org/LDP/abs/html/special-chars.html#DASHREF2)).
-The formatted code will be returned on stdout (unless `--check` was
-passed).  *Black* will still emit messages on stderr but that shouldn't
-affect your use case.
+Avoid using `args` in the hook. Instead, store necessary configuration in
+`pyproject.toml` so that editors and command-line usage of Black all behave consistently
+for your project. See _Black_'s own
+[pyproject.toml](https://github.com/psf/black/blob/master/pyproject.toml) for an
+example.

 
 

-This can be used for example with PyCharm's [File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html).
+If you're already using Python 3.7, switch the `language_version` accordingly. Finally,
+`stable` is a branch that tracks the latest release on PyPI. If you'd rather run on
+master, this is also an option.

 
 

+## GitHub Actions

 
 

-## Version control integration
+Create a file named `.github/workflows/black.yml` inside your repository with:

 
 

-Use [pre-commit](https://pre-commit.com/). Once you [have it
-installed](https://pre-commit.com/#install), add this to the
-`.pre-commit-config.yaml` in your repository:

 ```yaml
 ```yaml

-repos:
--   repo: https://github.com/ambv/black
-    rev: stable
-    hooks:
-    - id: black
-      language_version: python3.6
-```
-Then run `pre-commit install` and you're ready to go.
-
-Avoid using `args` in the hook.  Instead, store necessary configuration
-in `pyproject.toml` so that editors and command-line usage of Black all
-behave consistently for your project.  See *Black*'s own `pyproject.toml`
-for an example.
+name: Lint

 
 

-If you're already using Python 3.7, switch the `language_version`
-accordingly. Finally, `stable` is a tag that is pinned to the latest
-release on PyPI.  If you'd rather run on master, this is also an option.
+on: [push, pull_request]

 
 

+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+      - uses: psf/black@stable
+```

 
 ## Ignoring unmodified files
 
 
 ## Ignoring unmodified files
 

-*Black* remembers files it has already formatted, unless the `--diff` flag is used or
+_Black_ remembers files it has already formatted, unless the `--diff` flag is used or

 code is passed via standard input. This information is stored per-user. The exact
 code is passed via standard input. This information is stored per-user. The exact

-location of the file depends on the *Black* version and the system on which *Black*
-is run. The file is non-portable. The standard location on common operating systems
-is:
+location of the file depends on the _Black_ version and the system on which _Black_ is
+run. The file is non-portable. The standard location on common operating systems is:

 
 

-* Windows: `C:\\Users\<username>\AppData\Local\black\black\Cache\<version>\cache.<line-length>.<file-mode>.pickle`
-* macOS: `/Users/<username>/Library/Caches/black/<version>/cache.<line-length>.<file-mode>.pickle`
-* Linux: `/home/<username>/.cache/black/<version>/cache.<line-length>.<file-mode>.pickle`
+- Windows:
+  `C:\\Users\<username>\AppData\Local\black\black\Cache\<version>\cache.<line-length>.<file-mode>.pickle`
+- macOS:
+  `/Users/<username>/Library/Caches/black/<version>/cache.<line-length>.<file-mode>.pickle`
+- Linux:
+  `/home/<username>/.cache/black/<version>/cache.<line-length>.<file-mode>.pickle`

 
 `file-mode` is an int flag that determines whether the file was formatted as 3.6+ only,
 as .pyi, and whether string normalization was omitted.
 
 
 `file-mode` is an int flag that determines whether the file was formatted as 3.6+ only,
 as .pyi, and whether string normalization was omitted.
 

+To override the location of these files on macOS or Linux, set the environment variable
+`XDG_CACHE_HOME` to your preferred location. For example, if you want to put the cache
+in the directory you're running _Black_ from, set `XDG_CACHE_HOME=.cache`. _Black_ will
+then write the above files to `.cache/black/<version>/`.
+
+## Used by
+
+The following notable open-source projects trust _Black_ with enforcing a consistent
+code style: pytest, tox, Pyramid, Django Channels, Hypothesis, attrs, SQLAlchemy,
+Poetry, PyPA applications (Warehouse, Bandersnatch, Pipenv, virtualenv), pandas, Pillow,
+every Datadog Agent Integration, Home Assistant.
+
+The following organizations use _Black_: Facebook, Dropbox, Mozilla, Quora.
+
+Are we missing anyone? Let us know.

 
 ## Testimonials
 
 
 ## Testimonials
 

-**Dusty Phillips**, [writer](https://smile.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=dusty+phillips):
+**Dusty Phillips**,
+[writer](https://smile.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=dusty+phillips):

 
 

-> *Black* is opinionated so you don't have to be.
+> _Black_ is opinionated so you don't have to be.

 
 

-**Hynek Schlawack**, [creator of `attrs`](http://www.attrs.org/), core
-developer of Twisted and CPython:
+**Hynek Schlawack**, [creator of `attrs`](https://www.attrs.org/), core developer of
+Twisted and CPython:

 
 > An auto-formatter that doesn't suck is all I want for Xmas!
 
 
 > An auto-formatter that doesn't suck is all I want for Xmas!
 


@@ -795,413 +455,53 @@ developer of Twisted and CPython:
 
 > At least the name is good.
 
 
 > At least the name is good.
 

-**Kenneth Reitz**, creator of [`requests`](http://python-requests.org/)
-and [`pipenv`](https://docs.pipenv.org/):
+**Kenneth Reitz**, creator of [`requests`](http://python-requests.org/) and
+[`pipenv`](https://readthedocs.org/projects/pipenv/):

 
 > This vastly improves the formatting of our code. Thanks a ton!
 
 
 > This vastly improves the formatting of our code. Thanks a ton!
 

-

 ## Show your style
 
 Use the badge in your project's README.md:
 
 ```markdown
 ## Show your style
 
 Use the badge in your project's README.md:
 
 ```markdown

-[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black)
+[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)

 ```
 
 Using the badge in README.rst:
 ```
 
 Using the badge in README.rst:

+

 ```
 .. image:: https://img.shields.io/badge/code%20style-black-000000.svg
 ```
 .. image:: https://img.shields.io/badge/code%20style-black-000000.svg

-    :target: https://github.com/ambv/black
+    :target: https://github.com/psf/black

 ```
 
 ```
 

-Looks like this: [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black)
-
+Looks like this:
+[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)

 
 ## License
 
 MIT
 
 
 ## License
 
 MIT
 

+## Contributing to _Black_

 
 

-## Contributing to *Black*
-
-In terms of inspiration, *Black* is about as configurable as *gofmt*.
-This is deliberate.
-
-Bug reports and fixes are always welcome!  However, before you suggest a
-new feature or configuration knob, ask yourself why you want it.  If it
-enables better integration with some workflow, fixes an inconsistency,
-speeds things up, and so on - go for it!  On the other hand, if your
-answer is "because I don't like a particular formatting" then you're not
-ready to embrace *Black* yet. Such changes are unlikely to get accepted.
-You can still try but prepare to be disappointed.
-
-More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
-
-
-## Change Log
-
-### 18.8b0
-
-* numeric literals are now normalized to include `_` separators on Python 3.6+ code
-  (#452)
-
-* cache is now populated when `--check` is successful for a file which speeds up
-  consecutive checks of properly formatted unmodified files (#448)
-
-* fixed parsing of `__future__` imports with renames (#389)
-
-* fixed scope of `# fmt: off` when directly preceding `yield` and other nodes (#385)
-
-* note: the Vim plugin stopped registering ``,=`` as a default chord as it turned out
-  to be a bad idea (#415)
-
-
-### 18.6b4
-
-* hotfix: don't freeze when multiple comments directly precede `# fmt: off` (#371)
-
-
-### 18.6b3
-
-* typing stub files (`.pyi`) now have blank lines added after constants (#340)
-
-* `# fmt: off` and `# fmt: on` are now much more dependable:
-
-  * they now work also within bracket pairs (#329)
-
-  * they now correctly work across function/class boundaries (#335)
-
-  * they now work when an indentation block starts with empty lines or misaligned
-    comments (#334)
+In terms of inspiration, _Black_ is about as configurable as _gofmt_. This is
+deliberate.

 
 

-* made Click not fail on invalid environments; note that Click is right but the
-  likelihood we'll need to access non-ASCII file paths when dealing with Python source
-  code is low (#277)
+Bug reports and fixes are always welcome! However, before you suggest a new feature or
+configuration knob, ask yourself why you want it. If it enables better integration with
+some workflow, fixes an inconsistency, speeds things up, and so on - go for it! On the
+other hand, if your answer is "because I don't like a particular formatting" then you're
+not ready to embrace _Black_ yet. Such changes are unlikely to get accepted. You can
+still try but prepare to be disappointed.

 
 

-* fixed improper formatting of f-strings with quotes inside interpolated
-  expressions (#322)
+More details can be found in
+[CONTRIBUTING](https://github.com/psf/black/blob/master/CONTRIBUTING.md).

 
 

-* fixed unnecessary slowdown when long list literals where found in a file
+## Change log

 
 

-* fixed unnecessary slowdown on AST nodes with very many siblings
-
-* fixed cannibalizing backslashes during string normalization
-
-* fixed a crash due to symbolic links pointing outside of the project directory (#338)
-
-
-### 18.6b2
-
-* added `--config` (#65)
-
-* added `-h` equivalent to `--help` (#316)
-
-* fixed improper unmodified file caching when `-S` was used
-
-* fixed extra space in string unpacking (#305)
-
-* fixed formatting of empty triple quoted strings (#313)
-
-* fixed unnecessary slowdown in comment placement calculation on lines without
-  comments
-
-
-### 18.6b1
-
-* hotfix: don't output human-facing information on stdout (#299)
-
-* hotfix: don't output cake emoji on non-zero return code (#300)
-
-
-### 18.6b0
-
-* added `--include` and `--exclude` (#270)
-
-* added `--skip-string-normalization` (#118)
-
-* added `--verbose` (#283)
-
-* the header output in `--diff` now actually conforms to the unified diff spec
-
-* fixed long trivial assignments being wrapped in unnecessary parentheses (#273)
-
-* fixed unnecessary parentheses when a line contained multiline strings (#232)
-
-* fixed stdin handling not working correctly if an old version of Click was
-  used (#276)
-
-* *Black* now preserves line endings when formatting a file in place (#258)
-
-
-### 18.5b1
-
-* added `--pyi` (#249)
-
-* added `--py36` (#249)
-
-* Python grammar pickle caches are stored with the formatting caches, making
-  *Black* work in environments where site-packages is not user-writable (#192)
-
-* *Black* now enforces a PEP 257 empty line after a class-level docstring
-  (and/or fields) and the first method
-
-* fixed invalid code produced when standalone comments were present in a trailer
-  that was omitted from line splitting on a large expression (#237)
-
-* fixed optional parentheses being removed within `# fmt: off` sections (#224)
-
-* fixed invalid code produced when stars in very long imports were incorrectly
-  wrapped in optional parentheses (#234)
-
-* fixed unstable formatting when inline comments were moved around in
-  a trailer that was omitted from line splitting on a large expression
-  (#238)
-
-* fixed extra empty line between a class declaration and the first
-  method if no class docstring or fields are present (#219)
-
-* fixed extra empty line between a function signature and an inner
-  function or inner class (#196)
-
-
-### 18.5b0
-
-* call chains are now formatted according to the
-  [fluent interfaces](https://en.wikipedia.org/wiki/Fluent_interface)
-  style (#67)
-
-* data structure literals (tuples, lists, dictionaries, and sets) are
-  now also always exploded like imports when they don't fit in a single
-  line (#152)
-
-* slices are now formatted according to PEP 8 (#178)
-
-* parentheses are now also managed automatically on the right-hand side
-  of assignments and return statements (#140)
-
-* math operators now use their respective priorities for delimiting multiline
-  expressions (#148)
-
-* optional parentheses are now omitted on expressions that start or end
-  with a bracket and only contain a single operator (#177)
-
-* empty parentheses in a class definition are now removed (#145, #180)
-
-* string prefixes are now standardized to lowercase and `u` is removed
-  on Python 3.6+ only code and Python 2.7+ code with the `unicode_literals`
-  future import (#188, #198, #199)
-
-* typing stub files (`.pyi`) are now formatted in a style that is consistent
-  with PEP 484 (#207, #210)
-
-* progress when reformatting many files is now reported incrementally
-
-* fixed trailers (content with brackets) being unnecessarily exploded
-  into their own lines after a dedented closing bracket (#119)
-
-* fixed an invalid trailing comma sometimes left in imports (#185)
-
-* fixed non-deterministic formatting when multiple pairs of removable parentheses
-  were used (#183)
-
-* fixed multiline strings being unnecessarily wrapped in optional
-  parentheses in long assignments (#215)
-
-* fixed not splitting long from-imports with only a single name
-
-* fixed Python 3.6+ file discovery by also looking at function calls with
-  unpacking. This fixed non-deterministic formatting if trailing commas
-  where used both in function signatures with stars and function calls
-  with stars but the former would be reformatted to a single line.
-
-* fixed crash on dealing with optional parentheses (#193)
-
-* fixed "is", "is not", "in", and "not in" not considered operators for
-  splitting purposes
-
-* fixed crash when dead symlinks where encountered
-
-
-### 18.4a4
-
-* don't populate the cache on `--check` (#175)
-
-
-### 18.4a3
-
-* added a "cache"; files already reformatted that haven't changed on disk
-  won't be reformatted again (#109)
-
-* `--check` and `--diff` are no longer mutually exclusive (#149)
-
-* generalized star expression handling, including double stars; this
-  fixes multiplication making expressions "unsafe" for trailing commas (#132)
-
-* *Black* no longer enforces putting empty lines behind control flow statements
-  (#90)
-
-* *Black* now splits imports like "Mode 3 + trailing comma" of isort (#127)
-
-* fixed comment indentation when a standalone comment closes a block (#16, #32)
-
-* fixed standalone comments receiving extra empty lines if immediately preceding
-  a class, def, or decorator (#56, #154)
-
-* fixed `--diff` not showing entire path (#130)
-
-* fixed parsing of complex expressions after star and double stars in
-  function calls (#2)
-
-* fixed invalid splitting on comma in lambda arguments (#133)
-
-* fixed missing splits of ternary expressions (#141)
-
-
-### 18.4a2
-
-* fixed parsing of unaligned standalone comments (#99, #112)
-
-* fixed placement of dictionary unpacking inside dictionary literals (#111)
-
-* Vim plugin now works on Windows, too
-
-* fixed unstable formatting when encountering unnecessarily escaped quotes
-  in a string (#120)
-
-
-### 18.4a1
-
-* added `--quiet` (#78)
-
-* added automatic parentheses management (#4)
-
-* added [pre-commit](https://pre-commit.com) integration (#103, #104)
-
-* fixed reporting on `--check` with multiple files (#101, #102)
-
-* fixed removing backslash escapes from raw strings (#100, #105)
-
-
-### 18.4a0
-
-* added `--diff` (#87)
-
-* add line breaks before all delimiters, except in cases like commas, to
-  better comply with PEP 8 (#73)
-
-* standardize string literals to use double quotes (almost) everywhere
-  (#75)
-
-* fixed handling of standalone comments within nested bracketed
-  expressions; *Black* will no longer produce super long lines or put all
-  standalone comments at the end of the expression (#22)
-
-* fixed 18.3a4 regression: don't crash and burn on empty lines with
-  trailing whitespace (#80)
-
-* fixed 18.3a4 regression: `# yapf: disable` usage as trailing comment
-  would cause *Black* to not emit the rest of the file (#95)
-
-* when CTRL+C is pressed while formatting many files, *Black* no longer
-  freaks out with a flurry of asyncio-related exceptions
-
-* only allow up to two empty lines on module level and only single empty
-  lines within functions (#74)
-
-
-### 18.3a4
-
-* `# fmt: off` and `# fmt: on` are implemented (#5)
-
-* automatic detection of deprecated Python 2 forms of print statements
-  and exec statements in the formatted file (#49)
-
-* use proper spaces for complex expressions in default values of typed
-  function arguments (#60)
-
-* only return exit code 1 when --check is used (#50)
-
-* don't remove single trailing commas from square bracket indexing
-  (#59)
-
-* don't omit whitespace if the previous factor leaf wasn't a math
-  operator (#55)
-
-* omit extra space in kwarg unpacking if it's the first argument (#46)
-
-* omit extra space in [Sphinx auto-attribute comments](http://www.sphinx-doc.org/en/stable/ext/autodoc.html#directive-autoattribute)
-  (#68)
-
-
-### 18.3a3
-
-* don't remove single empty lines outside of bracketed expressions
-  (#19)
-
-* added ability to pipe formatting from stdin to stdin (#25)
-
-* restored ability to format code with legacy usage of `async` as
-  a name (#20, #42)
-
-* even better handling of numpy-style array indexing (#33, again)
-
-
-### 18.3a2
-
-* changed positioning of binary operators to occur at beginning of lines
-  instead of at the end, following [a recent change to PEP 8](https://github.com/python/peps/commit/c59c4376ad233a62ca4b3a6060c81368bd21e85b)
-  (#21)
-
-* ignore empty bracket pairs while splitting. This avoids very weirdly
-  looking formattings (#34, #35)
-
-* remove a trailing comma if there is a single argument to a call
-
-* if top level functions were separated by a comment, don't put four
-  empty lines after the upper function
-
-* fixed unstable formatting of newlines with imports
-
-* fixed unintentional folding of post scriptum standalone comments
-  into last statement if it was a simple statement (#18, #28)
-
-* fixed missing space in numpy-style array indexing (#33)
-
-* fixed spurious space after star-based unary expressions (#31)
-
-
-### 18.3a1
-
-* added `--check`
-
-* only put trailing commas in function signatures and calls if it's
-  safe to do so. If the file is Python 3.6+ it's always safe, otherwise
-  only safe if there are no `*args` or `**kwargs` used in the signature
-  or call. (#8)
-
-* fixed invalid spacing of dots in relative imports (#6, #13)
-
-* fixed invalid splitting after comma on unpacked variables in for-loops
-  (#23)
-
-* fixed spurious space in parenthesized set expressions (#7)
-
-* fixed spurious space after opening parentheses and in default
-  arguments (#14, #17)
-
-* fixed spurious space after unary operators when the operand was
-  a complex expression (#15)
-
-
-### 18.3a0
-
-* first published version, Happy 🍰 Day 2018!
-
-* alpha quality
-
-* date-versioned (see: https://calver.org/)
+The log's become rather long. It moved to its own file.

 
 

+See [CHANGES](https://github.com/psf/black/blob/master/CHANGES.md).

 
 ## Authors
 
 
 ## Authors
 


@@ -1210,24 +510,176 @@ Glued together by [Łukasz Langa](mailto:lukasz@langa.pl).
 Maintained with [Carol Willing](mailto:carolcode@willingconsulting.com),
 [Carl Meyer](mailto:carl@oddbird.net),
 [Jelle Zijlstra](mailto:jelle.zijlstra@gmail.com),
 Maintained with [Carol Willing](mailto:carolcode@willingconsulting.com),
 [Carl Meyer](mailto:carl@oddbird.net),
 [Jelle Zijlstra](mailto:jelle.zijlstra@gmail.com),

-[Mika Naylor](mailto:mail@autophagy.io), and
-[Zsolt Dollenstein](mailto:zsol.zsol@gmail.com).
+[Mika Naylor](mailto:mail@autophagy.io),
+[Zsolt Dollenstein](mailto:zsol.zsol@gmail.com), and
+[Cooper Lees](mailto:me@cooperlees.com).

 
 Multiple contributions by:
 
 Multiple contributions by:

-* [Anthony Sottile](mailto:asottile@umich.edu)
-* [Artem Malyshev](mailto:proofit404@gmail.com)
-* [Christian Heimes](mailto:christian@python.org)
-* [Daniel M. Capella](mailto:polycitizen@gmail.com)
-* [Eli Treuherz](mailto:eli.treuherz@cgi.com)
-* Hugo van Kemenade
-* [Ivan Katanić](mailto:ivan.katanic@gmail.com)
-* [Jonas Obrist](mailto:ojiidotch@gmail.com)
-* [Luka Sterbic](mailto:luka.sterbic@gmail.com)
-* [Miguel Gaiowski](mailto:miggaiowski@gmail.com)
-* [Miroslav Shubernetskiy](mailto:miroslav@miki725.com)
-* [Neraste](neraste.herr10@gmail.com)
-* [Osaetin Daniel](mailto:osaetindaniel@gmail.com)
-* [Peter Bengtsson](mailto:mail@peterbe.com)
-* [Stavros Korokithakis](mailto:hi@stavros.io)
-* [Sunil Kapil](mailto:snlkapil@gmail.com)
-* [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com)
+
+- [Abdur-Rahmaan Janhangeer](mailto:arj.python@gmail.com)
+- [Adam Johnson](mailto:me@adamj.eu)
+- [Adam Williamson](mailto:adamw@happyassassin.net)
+- [Alexander Huynh](mailto:github@grande.coffee)
+- [Alex Vandiver](mailto:github@chmrr.net)
+- [Allan Simon](mailto:allan.simon@supinfo.com)
+- Anders-Petter Ljungquist
+- [Andrew Thorp](mailto:andrew.thorp.dev@gmail.com)
+- [Andrew Zhou](mailto:andrewfzhou@gmail.com)
+- [Andrey](mailto:dyuuus@yandex.ru)
+- [Andy Freeland](mailto:andy@andyfreeland.net)
+- [Anthony Sottile](mailto:asottile@umich.edu)
+- [Arjaan Buijk](mailto:arjaan.buijk@gmail.com)
+- [Arnav Borbornah](mailto:arnavborborah11@gmail.com)
+- [Artem Malyshev](mailto:proofit404@gmail.com)
+- [Asger Hautop Drewsen](mailto:asgerdrewsen@gmail.com)
+- [Augie Fackler](mailto:raf@durin42.com)
+- [Aviskar KC](mailto:aviskarkc10@gmail.com)
+- Batuhan Taşkaya
+- [Benjamin Wohlwend](mailto:bw@piquadrat.ch)
+- [Benjamin Woodruff](mailto:github@benjam.info)
+- [Bharat Raghunathan](mailto:bharatraghunthan9767@gmail.com)
+- [Brandt Bucher](mailto:brandtbucher@gmail.com)
+- [Brett Cannon](mailto:brett@python.org)
+- [Bryan Bugyi](mailto:bryan.bugyi@rutgers.edu)
+- [Bryan Forbes](mailto:bryan@reigndropsfall.net)
+- [Calum Lind](mailto:calumlind@gmail.com)
+- [Charles](mailto:peacech@gmail.com)
+- Charles Reid
+- [Christian Clauss](mailto:cclauss@bluewin.ch)
+- [Christian Heimes](mailto:christian@python.org)
+- [Chuck Wooters](mailto:chuck.wooters@microsoft.com)
+- Codey Oxley
+- [Cong](mailto:congusbongus@gmail.com)
+- [Cooper Ry Lees](mailto:me@cooperlees.com)
+- [Dan Davison](mailto:dandavison7@gmail.com)
+- [Daniel Hahler](mailto:github@thequod.de)
+- [Daniel M. Capella](mailto:polycitizen@gmail.com)
+- Daniele Esposti
+- [David Hotham](mailto:david.hotham@metaswitch.com)
+- [David Lukes](mailto:dafydd.lukes@gmail.com)
+- [David Szotten](mailto:davidszotten@gmail.com)
+- [Denis Laxalde](mailto:denis@laxalde.org)
+- [Douglas Thor](mailto:dthor@transphormusa.com)
+- dylanjblack
+- [Eli Treuherz](mailto:eli@treuherz.com)
+- [Emil Hessman](mailto:emil@hessman.se)
+- [Felix Kohlgrüber](mailto:felix.kohlgrueber@gmail.com)
+- [Florent Thiery](mailto:fthiery@gmail.com)
+- Francisco
+- [Giacomo Tagliabue](mailto:giacomo.tag@gmail.com)
+- [Greg Gandenberger](mailto:ggandenberger@shoprunner.com)
+- [Gregory P. Smith](mailto:greg@krypto.org)
+- Gustavo Camargo
+- hauntsaninja
+- [Heaford](mailto:dan@heaford.com)
+- [Hugo Barrera](mailto::hugo@barrera.io)
+- Hugo van Kemenade
+- [Hynek Schlawack](mailto:hs@ox.cx)
+- [Ivan Katanić](mailto:ivan.katanic@gmail.com)
+- [Jakub Kadlubiec](mailto:jakub.kadlubiec@skyscanner.net)
+- [Jakub Warczarek](mailto:jakub.warczarek@gmail.com)
+- [Jan Hnátek](mailto:jan.hnatek@gmail.com)
+- [Jason Fried](mailto:me@jasonfried.info)
+- [Jason Friedland](mailto:jason@friedland.id.au)
+- [jgirardet](mailto:ijkl@netc.fr)
+- Jim Brännlund
+- [Jimmy Jia](mailto:tesrin@gmail.com)
+- [Joe Antonakakis](mailto:jma353@cornell.edu)
+- [Jon Dufresne](mailto:jon.dufresne@gmail.com)
+- [Jonas Obrist](mailto:ojiidotch@gmail.com)
+- [Jonty Wareing](mailto:jonty@jonty.co.uk)
+- [Jose Nazario](mailto:jose.monkey.org@gmail.com)
+- [Joseph Larson](mailto:larson.joseph@gmail.com)
+- [Josh Bode](mailto:joshbode@fastmail.com)
+- [Josh Holland](mailto:anowlcalledjosh@gmail.com)
+- [José Padilla](mailto:jpadilla@webapplicate.com)
+- [Juan Luis Cano Rodríguez](mailto:hello@juanlu.space)
+- [kaiix](mailto:kvn.hou@gmail.com)
+- [Katie McLaughlin](mailto:katie@glasnt.com)
+- Katrin Leinweber
+- [Keith Smiley](mailto:keithbsmiley@gmail.com)
+- [Kenyon Ralph](mailto:kenyon@kenyonralph.com)
+- [Kevin Kirsche](mailto:Kev.Kirsche+GitHub@gmail.com)
+- [Kyle Hausmann](mailto:kyle.hausmann@gmail.com)
+- [Kyle Sunden](mailto:sunden@wisc.edu)
+- Lawrence Chan
+- [Linus Groh](mailto:mail@linusgroh.de)
+- [Loren Carvalho](mailto:comradeloren@gmail.com)
+- [Luka Sterbic](mailto:luka.sterbic@gmail.com)
+- [LukasDrude](mailto:mail@lukas-drude.de)
+- Mahmoud Hossam
+- Mariatta
+- [Matt VanEseltine](mailto:vaneseltine@gmail.com)
+- [Matthew Clapp](mailto:itsayellow+dev@gmail.com)
+- [Matthew Walster](mailto:matthew@walster.org)
+- Max Smolens
+- [Michael Aquilina](mailto:michaelaquilina@gmail.com)
+- [Michael Flaxman](mailto:michael.flaxman@gmail.com)
+- [Michael J. Sullivan](mailto:sully@msully.net)
+- [Michael McClimon](mailto:michael@mcclimon.org)
+- [Miguel Gaiowski](mailto:miggaiowski@gmail.com)
+- [Mike](mailto:roshi@fedoraproject.org)
+- [mikehoyio](mailto:mikehoy@gmail.com)
+- [Min ho Kim](mailto:minho42@gmail.com)
+- [Miroslav Shubernetskiy](mailto:miroslav@miki725.com)
+- MomIsBestFriend
+- [Nathan Goldbaum](mailto:ngoldbau@illinois.edu)
+- [Nathan Hunt](mailtoneighthan.hunt@gmail.com)
+- [Neraste](mailto:neraste.herr10@gmail.com)
+- [Nikolaus Waxweiler](mailto:madigens@gmail.com)
+- [Ofek Lev](mailto:ofekmeister@gmail.com)
+- [Osaetin Daniel](mailto:osaetindaniel@gmail.com)
+- [otstrel](mailto:otstrel@gmail.com)
+- [Pablo Galindo](mailto:Pablogsal@gmail.com)
+- [Paul Ganssle](mailto:p.ganssle@gmail.com)
+- [Paul Meinhardt](mailto:mnhrdt@gmail.com)
+- [Peter Bengtsson](mailto:mail@peterbe.com)
+- [Peter Stensmyr](mailto:peter.stensmyr@gmail.com)
+- pmacosta
+- [Quentin Pradet](mailto:quentin@pradet.me)
+- [Ralf Schmitt](mailto:ralf@systemexit.de)
+- [Ramón Valles](mailto:mroutis@protonmail.com)
+- [Richard Fearn](mailto:richardfearn@gmail.com)
+- Richard Si
+- [Rishikesh Jha](mailto:rishijha424@gmail.com)
+- [Rupert Bedford](mailto:rupert@rupertb.com)
+- Russell Davis
+- [Rémi Verschelde](mailto:rverschelde@gmail.com)
+- [Sami Salonen](mailto:sakki@iki.fi)
+- [Samuel Cormier-Iijima](mailto:samuel@cormier-iijima.com)
+- [Sanket Dasgupta](mailto:sanketdasgupta@gmail.com)
+- Sergi
+- [Scott Stevenson](mailto:scott@stevenson.io)
+- Shantanu
+- [shaoran](mailto:shaoran@sakuranohana.org)
+- [Shinya Fujino](mailto:shf0811@gmail.com)
+- springstan
+- [Stavros Korokithakis](mailto:hi@stavros.io)
+- [Stephen Rosen](mailto:sirosen@globus.org)
+- [Steven M. Vascellaro](mailto:S.Vascellaro@gmail.com)
+- [Sunil Kapil](mailto:snlkapil@gmail.com)
+- [Sébastien Eustace](mailto:sebastien.eustace@gmail.com)
+- [Tal Amuyal](mailto:TalAmuyal@gmail.com)
+- [Terrance](mailto:git@terrance.allofti.me)
+- [Thom Lu](mailto:thomas.c.lu@gmail.com)
+- [Thomas Grainger](mailto:tagrain@gmail.com)
+- [Tim Gates](mailto:tim.gates@iress.com)
+- [Tim Swast](mailto:swast@google.com)
+- [Timo](mailto:timo_tk@hotmail.com)
+- Toby Fleming
+- [Tom Christie](mailto:tom@tomchristie.com)
+- [Tony Narlock](mailto:tony@git-pull.com)
+- [Tsuyoshi Hombashi](mailto:tsuyoshi.hombashi@gmail.com)
+- [Tushar Chandra](mailto:tusharchandra2018@u.northwestern.edu)
+- [Tzu-ping Chung](mailto:uranusjr@gmail.com)
+- [Utsav Shah](mailto:ukshah2@illinois.edu)
+- utsav-dbx
+- vezeli
+- [Ville Skyttä](mailto:ville.skytta@iki.fi)
+- [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com)
+- [Vlad Emelianov](mailto:volshebnyi@gmail.com)
+- [williamfzc](mailto:178894043@qq.com)
+- [wouter bolsterlee](mailto:wouter@bolsterl.ee)
+- Yazdan
+- [Yngve Høiseth](mailto:yngve@hoiseth.net)
+- [Yurii Karabas](mailto:1998uriyyo@gmail.com)