Test on Python 3.8 final (#1070)

[etc/vim.git] / README.md

diff --git a/README.md b/README.md
index fc1db130812885e3f9dcf4dcd2ba9a60349c5ac8..76ae9cfee788c5746e06db7bf57d8e9d37493397 100644 (file)
--- a/README.md
+++ b/README.md
@@ -1,20 +1,21 @@
-![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="http://black.readthedocs.io/en/latest/?badge=latest"><img alt="Documentation Status" src="http://readthedocs.org/projects/black/badge/?version=latest"></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="http://black.readthedocs.io/en/latest/_static/license.svg"></a>
-<a href="https://pypi.python.org/pypi/black"><img alt="PyPI" src="http://black.readthedocs.io/en/latest/_static/pypi.svg"></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://travis-ci.com/psf/black"><img alt="Build Status" src="https://travis-ci.com/psf/black.svg?branch=master"></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/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://black.readthedocs.io/en/stable/_static/pypi.svg"></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.”
 
 
 *Black* is the uncompromising Python code formatter.  By using it, you
 </p>
 
 > “Any color you like.”
 
 
 *Black* is the uncompromising Python code formatter.  By using it, you

-agree to cease control over minutiae of hand-formatting.  In return,
+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* gives you speed, determinism, and freedom from `pycodestyle`
 nagging about formatting.  You will save time and mental energy for
 more important matters.


@@ -26,8 +27,28 @@ 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).
+Watch the [PyCon 2019 talk](https://youtu.be/esZLCuWs_2Y) to learn more.

 
 

-## Installation and Usage
+---
+
+*Contents:* **[Installation and usage](#installation-and-usage)** |
+**[Code style](#the-black-code-style)** |
+**[pyproject.toml](#pyprojecttoml)** |
+**[Editor integration](#editor-integration)** |
+**[blackd](#blackd)** |
+**[Version control integration](#version-control-integration)** |
+**[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)**
+
+---
+
+## Installation and usage

 
 ### Installation
 
 
 ### Installation
 


@@ -45,28 +66,66 @@ black {source_file_or_directory}
 
 ### Command line options
 
 
 ### Command line options
 

-Black doesn't provide many options.  You can list them by running
+*Black* doesn't provide many options.  You can list them by running

 `black --help`:
 
 ```text
 black [OPTIONS] [SRC]...
 
 Options:
 `black --help`:
 
 ```text
 black [OPTIONS] [SRC]...
 
 Options:

-  -l, --line-length INTEGER   Where to wrap around.  [default: 88]
-  --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]
-  -q, --quiet                 Don't emit non-error messages to stderr. Errors
-                              are still emitted, silence those with
-                              2>/dev/null.
-  --version                   Show the version and exit.
-  --help                      Show this message and exit.
+  -c, --code TEXT                 Format the code passed in as a string.
+  -l, --line-length INTEGER       How many characters per line to allow.
+                                  [default: 88]
+  -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]
+  --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. Deprecated; use
+                                  --target-version instead. [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.  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|_build|buck-
+                                  out|build|dist)/]
+  -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.
+  -h, --help                      Show this message and exit.

 ```
 
 *Black* is a well-behaved Unix-style command-line tool:
 ```
 
 *Black* is a well-behaved Unix-style command-line tool:


@@ -74,18 +133,20 @@ Options:
 * 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;
 * 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 occured (or `--check` was
+* exits with code 0 unless an internal error occurred (or `--check` was

   used).
 
 
   used).
 
 

-### NOTE: This is an early pre-release
+### NOTE: This is a beta product

 
 

-*Black* can already successfully format itself and the standard library.
+*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
 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

-"Alpha" trove classifier, as well as by the "a" in the version number.
+"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,
 What this means for you is that **until the formatter becomes stable,

-you should expect some formatting to change in the future**.
+you should expect some formatting to change in the future**.  That being
+said, no drastic stylistic changes are planned, mostly responses to bug
+reports.

 
 Also, as a temporary safety measure, *Black* will check that the
 reformatted code still produces a valid AST that is equivalent to the
 
 Also, as a temporary safety measure, *Black* will check that the
 reformatted code still produces a valid AST that is equivalent to the


@@ -97,7 +158,8 @@ original.  This slows it down.  If you're feeling confident, use
 
 *Black* reformats entire files in place.  It is not configurable.  It
 doesn't take previous formatting into account.  It doesn't reformat
 
 *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
+blocks that start with `# fmt: off` and end with `# fmt: on`. `# fmt: on/off`
+have to be on the same level of indentation. It also

 recognizes [YAPF](https://github.com/google/yapf)'s block comments to
 the same effect, as a courtesy for straddling code.
 
 recognizes [YAPF](https://github.com/google/yapf)'s block comments to
 the same effect, as a courtesy for straddling code.
 


@@ -106,9 +168,9 @@ the same effect, as a courtesy for straddling code.
 
 *Black* ignores previous formatting and applies uniform horizontal
 and vertical whitespace to your code.  The rules for horizontal
 
 *Black* ignores previous formatting and applies uniform horizontal
 and vertical whitespace to your code.  The rules for horizontal

-whitespace are pretty obvious and 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.
+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.

 
 As for vertical whitespace, *Black* tries to render one full expression
 or simple statement per line.  If this fits the allotted line length,
 
 As for vertical whitespace, *Black* tries to render one full expression
 or simple statement per line.  If this fits the allotted line length,


@@ -116,14 +178,14 @@ great.
 ```py3
 # in:
 
 ```py3
 # in:
 

-l = [1,
+j = [1,

      2,
      3,
 ]
 
 # out:
 
      2,
      3,
 ]
 
 # out:
 

-l = [1, 2, 3]
+j = [1, 2, 3]

 ```
 
 If not, *Black* will look at the contents of the first outer matching
 ```
 
 If not, *Black* will look at the contents of the first outer matching


@@ -131,13 +193,13 @@ brackets and put that in a separate indented line.
 ```py3
 # in:
 
 ```py3
 # in:
 

-l = [[n for n in list_bosses()], [n for n in list_employees()]]
+ImportantClass.important_method(exc, limit, lookup_lines, capture_locals, extra_argument)

 
 # out:
 
 
 # out:
 

-l = [
-    [n for n in list_bosses()], [n for n in list_employees()]
-]
+ImportantClass.important_method(
+    exc, limit, lookup_lines, capture_locals, extra_argument
+)

 ```
 
 If that still doesn't fit the bill, it will decompose the internal
 ```
 
 If that still doesn't fit the bill, it will decompose the internal


@@ -150,7 +212,7 @@ separate lines.
 ```py3
 # in:
 
 ```py3
 # in:
 

-def very_important_function(template: str, *variables, file: os.PathLike, debug: bool = False):
+def very_important_function(template: str, *variables, file: os.PathLike, engine: str, header: bool = True, debug: bool = False):

     """Applies `variables` to the `template` and writes to `file`."""
     with open(file, 'w') as f:
         ...
     """Applies `variables` to the `template` and writes to `file`."""
     with open(file, 'w') as f:
         ...


@@ -161,6 +223,8 @@ def very_important_function(
     template: str,
     *variables,
     file: os.PathLike,
     template: str,
     *variables,
     file: os.PathLike,

+    engine: str,
+    header: bool = True,

     debug: bool = False,
 ):
     """Applies `variables` to the `template` and writes to `file`."""
     debug: bool = False,
 ):
     """Applies `variables` to the `template` and writes to `file`."""


@@ -176,6 +240,30 @@ 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).
 
 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.
+
+<details>
+<summary>A compatible `.isort.cfg`</summary>
+
+```
+[settings]
+multi_line_output=3
+include_trailing_comma=True
+force_grid_wrap=0
+use_parentheses=True
+line_length=88
+```
+
+The equivalent command line is:
+```
+$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --use-parentheses --line-width=88 [ file.py ]
+```
+</details>

 
 ### Line length
 
 
 ### Line length
 


@@ -205,11 +293,12 @@ you are probably already using.  You'd do it like this:
 max-line-length = 80
 ...
 select = C,E,F,W,B,B950
 max-line-length = 80
 ...
 select = C,E,F,W,B,B950

-ignore = E501
+ignore = E501,W503,E203

 ```
 
 You'll find *Black*'s own .flake8 config file is configured like this.
 ```
 
 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
+If you're curious about the reasoning behind B950,
+[Bugbear's documentation](https://github.com/PyCQA/flake8-bugbear#opinionated-warnings)

 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".
 
 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".
 


@@ -218,10 +307,7 @@ bother you if you overdo it by a few km/h".
 
 *Black* avoids spurious vertical whitespace.  This is in the spirit of
 PEP 8 which says that in-function vertical whitespace should only be
 
 *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.  One exception is control flow statements: *Black* will
-always emit an extra empty line after ``return``, ``raise``, ``break``,
-``continue``, and ``yield``.  This is to make changes in control flow
-more prominent to readers of your code.
+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
 
 *Black* will allow single empty lines inside functions, and single and
 double empty lines on module level left by the original editors, except


@@ -230,11 +316,17 @@ 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
 
 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.  *Black* will put those empty lines also
-between the function definition and any standalone comments that
-immediately precede the given function.  If you want to comment on the
-entire function, use a docstring or put a leading comment in the function
-body.
+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.
+
+*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.

 
 
 ### Trailing commas
 
 
 ### Trailing commas


@@ -265,21 +357,27 @@ 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.
 
 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.
 
 ### 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
 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).
+[#26](https://github.com/psf/black/issues/26) for details).

 
 Why settle on double quotes?  They anticipate apostrophes in English
 
 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
+text.  They match the docstring standard described in [PEP 257](https://www.python.org/dev/peps/pep-0257/#what-is-a-docstring).
+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.
 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.


@@ -289,7 +387,21 @@ 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.
 
 key.  My recommendation here is to keep using whatever is faster to type
 and let *Black* handle the transformation.
 

-### Line Breaks & Binary Operators
+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.
+
+### Numeric literals
+
+*Black* standardizes most numeric literals to use lowercase letters for the
+syntactic parts and uppercase letters for the digits themselves: `0xAB`
+instead of `0XAB` and `1e10` instead of `1E10`. Python 2 long literals are
+styled as `2L` instead of `2l` to avoid confusion between `l` and `1`.
+
+
+### 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
 
 *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


@@ -300,6 +412,21 @@ 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.
 
 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
 ### Parentheses
 
 Some parentheses are optional in the Python grammar.  Any expression can


@@ -311,54 +438,285 @@ interesting cases:
 - `for (...) in (...):`
 - `assert (...), (...)`
 - `from X import (...)`
 - `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
 
 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.  Otherwise, the parentheses are always added.
+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)
+```
+
+
+### 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()
+    )
+```
+
+
+### 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]`.
+
+
+## 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.
+
+
+### 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.
+
+
+### 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.
+
+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.
+
+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
+
+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.
+
+<details>
+<summary>Example `pyproject.toml`</summary>
+
+```toml
+[tool.black]
+line-length = 88
+target-version = ['py37']
+include = '\.pyi?$'
+exclude = '''
+
+(
+  /(
+      \.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
+)
+'''
+```
+
+</details>
+
+### 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.

 
 
 ## Editor integration
 
 ### Emacs
 
 
 
 ## Editor integration
 
 ### Emacs
 

-Use [proofit404/blacken](https://github.com/proofit404/blacken).
+Use [proofit404/blacken](https://github.com/proofit404/blacken) or
+[Elpy](https://github.com/jorgenschaefer/elpy).

 
 
 
 

-### PyCharm
+### PyCharm/IntelliJ IDEA

 
 1. Install `black`.
 
 
 1. Install `black`.
 

-        $ pip install black
+```console
+$ pip install black
+```

 
 2. Locate your `black` installation folder.
 
 
 2. Locate your `black` installation folder.
 

-  On MacOS / Linux / BSD:
+  On macOS / Linux / BSD:

 
 

-        $ which black
-        /usr/local/bin/black  # possible location
+```console
+$ which black
+/usr/local/bin/black  # possible location
+```

 
   On Windows:
 
 
   On Windows:
 

-        $ where black
-        %LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe  # possible location
+```console
+$ where black
+%LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe  # possible location
+```
+
+3. Open External tools in PyCharm/IntelliJ IDEA

 
 

-3. Open External tools in PyCharm with `File -> Settings -> Tools -> External Tools`.
+  On macOS:
+
+```PyCharm -> Preferences -> Tools -> External Tools```
+
+  On Windows / Linux / BSD:
+
+```File -> Settings -> Tools -> External Tools```

 
 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>
 
 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: $FilePath$
+    - Arguments: `"$FilePath$"`

 
 5. Format the currently opened file by selecting `Tools -> External Tools -> black`.
 
 5. Format the currently opened file by selecting `Tools -> External Tools -> black`.

-    - Alternatively, you can set a keyboard shortcut by navigating to `Preferences -> Keymap`.
+    - Alternatively, you can set a keyboard shortcut by navigating to `Preferences or Settings -> Keymap -> External Tools -> External Tools - Black`.
+
+6. Optionally, run *Black* on every file save:

 
 

+    1. Make sure you have the [File Watcher](https://plugins.jetbrains.com/plugin/7177-file-watchers) plugin installed.
+    2. Go to `Preferences or Settings -> 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: `$FilePath$`
+        - Working directory: `$ProjectFileDir$`
+       - Uncheck "Auto-save edited files to trigger the watcher"
+
+
+
+### Wing IDE
+
+Wing supports black via the OS Commands tool, as explained in the Wing documentation on [pep8 formatting](https://wingware.com/doc/edit/pep8). The detailed procedure is:
+
+1. Install `black`.
+
+```console
+$ pip install black
+```
+
+2. Make sure it runs from the command line, e.g.
+
+```console
+$ black --help
+```
+
+3. In Wing IDE, activate the **OS Commands** panel  and define the command  **black** to execute black on the currently selected file:
+
+- Use the Tools -> OS Commands menu selection
+- click on **+** in **OS Commands** -> New: Command line..
+  - Title: black
+  - Command Line: black %s
+  - I/O Encoding: Use Default
+  - Key Binding: F1
+  - [x] Raise OS Commands when executed
+  - [x] Auto-save files before execution
+  - [x] Line mode
+
+4. Select a file in the editor and press **F1** , or whatever key binding you selected in step 3, to reformat the file.

 
 ### Vim
 
 Commands and shortcuts:
 
 
 ### Vim
 
 Commands and shortcuts:
 

-* `,=` or `:Black` to format the entire file (ranges not supported);
+* `: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.
 * `:BlackUpgrade` to upgrade *Black* inside the virtualenv;
 * `:BlackVersion` to get the current version of *Black* inside the
   virtualenv.


@@ -366,11 +724,24 @@ Commands and shortcuts:
 Configuration:
 * `g:black_fast` (defaults to `0`)
 * `g:black_linelength` (defaults to `88`)
 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`)
 
 * `g:black_virtualenv` (defaults to `~/.vim/black`)
 

-To install, copy the plugin from [vim/plugin/black.vim](https://github.com/ambv/black/tree/master/vim/plugin/black.vim).
+To install with [vim-plug](https://github.com/junegunn/vim-plug):
+
+```
+Plug 'psf/black'
+```
+
+or with [Vundle](https://github.com/VundleVim/Vundle.vim):
+
+```
+Plugin 'psf/black'
+```
+
+or you can copy the plugin from [plugin/black.vim](https://github.com/psf/black/tree/master/plugin/black.vim).

 Let me know if this requires any changes to work with Vim 8's builtin
 Let me know if this requires any changes to work with Vim 8's builtin

-`packadd`, or Pathogen, or Vundle, and so on.
+`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
 
 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


@@ -381,13 +752,19 @@ 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
 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), just
+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.
 
 create a virtualenv manually and point `g:black_virtualenv` to it.
 The plugin will use it.
 

+To run *Black* on save, add the following line to `.vimrc` or `init.vim`:
+
+```
+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.
 **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`.
+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.
 When building Vim from source, use:
 `./configure --enable-python3interp=yes`. There's many guides online how
 to do this.


@@ -395,24 +772,129 @@ to do this.
 
 ### Visual Studio Code
 
 
 ### Visual Studio Code
 

-Use [joslarson.black-vscode](https://marketplace.visualstudio.com/items?itemName=joslarson.black-vscode).
+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).
+
+
+### Jupyter 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 [python-black](https://atom.io/packages/python-black).

 
 
 ### Other editors
 
 
 
 ### Other editors
 

-Atom/Nuclide integration is planned by the author, others will
-require external contributions.
+Other editors will require external contributions.

 
 Patches welcome! ✨ 🍰 ✨
 
 Any tool that can pipe code through *Black* using its stdio mode (just
 
 Patches welcome! ✨ 🍰 ✨
 
 Any tool that can pipe code through *Black* using its stdio mode (just

-[use `-` as the file name](http://www.tldp.org/LDP/abs/html/special-chars.html#DASHREF2)).
+[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.
 
 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.
 

-This can be used for example with PyCharm's [File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html).
+This can be used for example with PyCharm's or IntelliJ's [File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html).
+
+## blackd
+
+`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.
+
+### Usage
+
+`blackd` is not packaged alongside *Black* by default because it has additional
+dependencies. You will need to do `pip install black[d]` to install it.
+
+You can start the server on the default port, binding only to the local interface
+by running `blackd`. You will see a single line mentioning the server's version,
+and the host and port it's listening on. `blackd` will then print an access log
+similar to most web servers on standard output, merged with any exception traces
+caused by invalid formatting requests.
+
+`blackd` provides even less options than *Black*. You can see them by running
+`blackd --help`:
+
+```text
+Usage: blackd [OPTIONS]
+
+Options:
+  --bind-host TEXT                Address to bind the server to.
+  --bind-port INTEGER             Port to listen on
+  --version                       Show the version and exit.
+  -h, --help                      Show this message and exit.
+```
+
+There is no official blackd client tool (yet!). You can test that blackd is
+working using `curl`:
+
+```
+blackd --bind-port 9090 &  # or let blackd choose a port
+curl -s -XPOST "localhost:9090" -d "print('valid')"
+```

 
 

+### Protocol
+
+`blackd` only accepts `POST` requests at the `/` path. The body of the request
+should contain the python source code to be formatted, encoded
+according to the `charset` field in the `Content-Type` request header. If no
+`charset` is specified, `blackd` assumes `UTF-8`.
+
+There are a few HTTP headers that control how the source is formatted. These
+correspond to command line flags for *Black*. There is one exception to this:
+`X-Protocol-Version` which if present, should have the value `1`, otherwise the
+request is rejected with `HTTP 501` (Not Implemented).
+
+The headers controlling how code is formatted are:
+
+ - `X-Line-Length`: corresponds to the `--line-length` command line flag.
+ - `X-Skip-String-Normalization`: corresponds to the `--skip-string-normalization`
+    command line flag. If present and its value is not the empty string, no string
+    normalization will be performed.
+ - `X-Fast-Or-Safe`: if set to `fast`, `blackd` will act as *Black* does when
+    passed the `--fast` command line flag.
+ - `X-Python-Variant`: if set to `pyi`, `blackd` will act as *Black* does when
+    passed the `--pyi` command line flag. Otherwise, its value must correspond to
+    a Python version or a set of comma-separated Python versions, optionally
+    prefixed with `py`. For example, to request code that is compatible
+    with Python 3.5 and 3.6, set the header to `py3.5,py3.6`.
+
+If any of these headers are set to invalid values, `blackd` returns a `HTTP 400`
+error response, mentioning the name of the problematic header in the message body.
+
+Apart from the above, `blackd` can produce the following response codes:
+
+ - `HTTP 204`: If the input is already well-formatted. The response body is
+       empty.
+ - `HTTP 200`: If formatting was needed on the input. The response body
+       contains the blackened Python code, and the `Content-Type` header is set
+       accordingly.
+ - `HTTP 400`: If the input contains a syntax error. Details of the error are
+       returned in the response body.
+ - `HTTP 500`: If there was any kind of error while trying to format the input.
+       The response body contains a textual representation of the error.
+
+The response headers include a `X-Black-Version` header containing the version
+of *Black*.

 
 ## Version control integration
 
 
 ## Version control integration
 


@@ -421,28 +903,61 @@ installed](https://pre-commit.com/#install), add this to the
 `.pre-commit-config.yaml` in your repository:
 ```yaml
 repos:
 `.pre-commit-config.yaml` in your repository:
 ```yaml
 repos:

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

     rev: stable
     hooks:
     - id: black
     rev: stable
     hooks:
     - id: black

-      args: [--line-length=88, --safe]
-      python_version: python3.6
+      language_version: python3.6

 ```
 Then run `pre-commit install` and you're ready to go.
 
 ```
 Then run `pre-commit install` and you're ready to go.
 

-`args` in the above config is optional but shows you how you can change
-the line length if you really need to.  If you're already using Python
-3.7, switch the `python_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.
+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](/pyproject.toml)
+for an example.
+
+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.
+
+
+## Ignoring unmodified files
+
+*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
+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`
+
+`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, Pipenv, virtualenv),
+pandas, Pillow, every Datadog Agent Integration.
+
+Are we missing anyone?  Let us know.
+

 
 ## Testimonials
 
 **Dusty Phillips**, [writer](https://smile.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=dusty+phillips):
 
 
 ## Testimonials
 
 **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
+**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!
 developer of Twisted and CPython:
 
 > An auto-formatter that doesn't suck is all I want for Xmas!


@@ -462,10 +977,16 @@ and [`pipenv`](https://docs.pipenv.org/):
 Use the badge in your project's README.md:
 
 ```markdown
 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:
+```
+.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
+    :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
 
 
 ## License


@@ -473,10 +994,10 @@ Looks like this: [![Code style: black](https://img.shields.io/badge/code%20style
 MIT
 
 
 MIT
 
 

-## Contributing to Black
+## Contributing to *Black*

 
 

-In terms of inspiration, *Black* is about as configurable as *gofmt* and
-*rustfmt* are.  This is deliberate.
+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
 
 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


@@ -491,13 +1012,322 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
 
 ## Change Log
 
 
 ## Change Log
 

+### unreleased
+
+* added `black -c` as a way to format code passed from the command line
+  (#761)
+
+* --safe now works with Python 2 code (#840)
+
+* fixed grammar selection for Python 2-specific code (#765)
+
+* fixed feature detection for trailing commas in function definitions
+  and call sites (#763)
+
+* *Black* can now format async generators (#593)
+
+* *Black* no longer crashes on Windows machines with more than 61 cores
+  (#838)
+
+* *Black* no longer crashes on standalone comments prepended with
+  a backslash (#767)
+
+* *Black* no longer crashes on `from` ... `import` blocks with comments
+  (#829)
+
+* removed unnecessary parentheses around `yield` expressions (#834)
+
+* added parentheses around long tuples in unpacking assignments (#832)
+
+* fixed bug that led *Black* format some code with a line length target
+  of 1 (#762)
+
+* *Black* no longer introduces quotes in f-string subexpressions on string
+  boundaries (#863)
+
+* if *Black* puts parenthesis around a single expression, it moves comments
+  to the wrapped expression instead of after the brackets (#872)
+
+* *Black* is now able to format Python code that uses assignment expressions
+  (`:=` as described in PEP-572) (#935)
+
+* *Black* is now able to format Python code that uses positional-only
+  arguments (`/` as described in PEP-570) (#946)
+
+* `blackd` now returns the version of *Black* in the response headers (#1013)
+
+
+### 19.3b0
+
+* new option `--target-version` to control which Python versions
+  *Black*-formatted code should target (#618)
+
+* deprecated `--py36` (use `--target-version=py36` instead) (#724)
+
+* *Black* no longer normalizes numeric literals to include `_` separators (#696)
+
+* long `del` statements are now split into multiple lines (#698)
+
+* type comments are no longer mangled in function signatures
+
+* improved performance of formatting deeply nested data structures (#509)
+
+* *Black* now properly formats multiple files in parallel on
+  Windows (#632)
+
+* *Black* now creates cache files atomically which allows it to be used
+  in parallel pipelines (like `xargs -P8`) (#673)
+
+* *Black* now correctly indents comments in files that were previously
+  formatted with tabs (#262)
+
+* `blackd` now supports CORS (#622)
+
+
+### 18.9b0
+
+* numeric literals are now formatted by *Black* (#452, #461, #464, #469):
+
+  * numeric literals are normalized to include `_` separators on Python 3.6+ code
+
+  * added `--skip-numeric-underscore-normalization` to disable the above behavior and
+    leave numeric underscores as they were in the input
+
+  * code with `_` in numeric literals is recognized as Python 3.6+
+
+  * most letters in numeric literals are lowercased (e.g., in `1e10`, `0x01`)
+
+  * hexadecimal digits are always uppercased (e.g. `0xBADC0DE`)
+
+* added `blackd`, see [its documentation](#blackd) for more info (#349)
+
+* adjacent string literals are now correctly split into multiple lines (#463)
+
+* trailing comma is now added to single imports that don't fit on a line (#250)
+
+* cache is now populated when `--check` is successful for a file which speeds up
+  consecutive checks of properly formatted unmodified files (#448)
+
+* whitespace at the beginning of the file is now removed (#399)
+
+* fixed mangling [pweave](http://mpastell.com/pweave/) and
+  [Spyder IDE](https://pythonhosted.org/spyder/) special comments (#532)
+
+* fixed unstable formatting when unpacking big tuples (#267)
+
+* fixed parsing of `__future__` imports with renames (#389)
+
+* fixed scope of `# fmt: off` when directly preceding `yield` and other nodes (#385)
+
+* fixed formatting of lambda expressions with default arguments (#468)
+
+* fixed ``async for`` statements: *Black* no longer breaks them into separate
+  lines (#372)
+
+* 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)
+
+* 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)
+
+* fixed improper formatting of f-strings with quotes inside interpolated
+  expressions (#322)
+
+* fixed unnecessary slowdown when long list literals where found in a file
+
+* 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
 
 ### 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)
 
 * generalized star expression handling, including double stars; this
   fixes multiplication making expressions "unsafe" for trailing commas (#132)
 

-* fix parsing of complex expressions after star and double stars in 
-  function parameters (#2)
+* *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
 
 
 ### 18.4a2
 


@@ -535,16 +1365,16 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
   (#75)
 
 * fixed handling of standalone comments within nested bracketed
   (#75)
 
 * fixed handling of standalone comments within nested bracketed

-  expressions; Black will no longer produce super long lines or put all
+  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
   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)
+  would cause *Black* to not emit the rest of the file (#95)

 
 

-* when CTRL+C is pressed while formatting many files, Black no longer
+* 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
   freaks out with a flurry of asyncio-related exceptions
 
 * only allow up to two empty lines on module level and only single empty


@@ -591,7 +1421,7 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
 ### 18.3a2
 
 * changed positioning of binary operators to occur at beginning of lines
 ### 18.3a2
 
 * changed positioning of binary operators to occur at beginning of lines

-  instead of at the end, following [a recent change to PEP8](https://github.com/python/peps/commit/c59c4376ad233a62ca4b3a6060c81368bd21e85b)
+  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
   (#21)
 
 * ignore empty bracket pairs while splitting. This avoids very weirdly


@@ -650,14 +1480,30 @@ Glued together by [Łukasz Langa](mailto:lukasz@langa.pl).
 
 Maintained with [Carol Willing](mailto:carolcode@willingconsulting.com),
 [Carl Meyer](mailto:carl@oddbird.net),
 
 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).
 
 Multiple contributions by:
 * [Anthony Sottile](mailto:asottile@umich.edu)
 * [Artem Malyshev](mailto:proofit404@gmail.com)
 [Mika Naylor](mailto:mail@autophagy.io), and
 [Zsolt Dollenstein](mailto:zsol.zsol@gmail.com).
 
 Multiple contributions by:
 * [Anthony Sottile](mailto:asottile@umich.edu)
 * [Artem Malyshev](mailto:proofit404@gmail.com)

+* [Benjamin Woodruff](mailto:github@benjam.info)
+* [Christian Heimes](mailto:christian@python.org)

 * [Daniel M. Capella](mailto:polycitizen@gmail.com)
 * [Daniel M. Capella](mailto:polycitizen@gmail.com)

-* [Eli Treuherz](mailto:eli.treuherz@cgi.com)
+* [Eli Treuherz](mailto:eli@treuherz.com)
+* hauntsaninja

 * Hugo van Kemenade
 * [Ivan Katanić](mailto:ivan.katanic@gmail.com)
 * Hugo van Kemenade
 * [Ivan Katanić](mailto:ivan.katanic@gmail.com)

+* [Jason Fried](mailto:me@jasonfried.info)
+* [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](mailto:neraste.herr10@gmail.com)

 * [Osaetin Daniel](mailto:osaetindaniel@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)
+* [Utsav Shah](mailto:ukshah2@illinois.edu)
+* [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com)
+* [Chuck Wooters](mailto:chuck.wooters@microsoft.com)