X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/de860cccf1af23bc8c4f04474fa26bdf04f6e350..41368138bbc69fd805dfc931f165e9488fc9986c:/README.md?ds=sidebyside
diff --git a/README.md b/README.md
index 56321c7..244f60d 100644
--- a/README.md
+++ b/README.md
@@ -1,12 +1,21 @@
-# black
+
+The Uncompromising Code Formatter
-[](https://travis-ci.org/ambv/black)
+
+
+
+
+
+
+
+
+
-> Any color you like.
+> âAny color you like.â
*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.
@@ -18,39 +27,117 @@ content instead.
*Black* makes code review faster by producing the smallest diffs
possible.
+Try it out now using the [Black Playground](https://black.now.sh).
-## NOTE: This is an early pre-release
+---
-*Black* can already successfully format itself and the standard library.
-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.
-What this means for you is that **until the formatter becomes stable,
-you should expect some formatting to change in the future**.
+*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)** |
+**[Testimonials](#testimonials)** |
+**[Show your style](#show-your-style)** |
+**[Contributing](#contributing-to-black)** |
+**[Change Log](#change-log)** |
+**[Authors](#authors)**
-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``.
+---
+
+## Installation and usage
+
+### 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.
-## Usage
+### Usage
-*Black* can be installed by running `pip install black`.
+To get started right away with sensible defaults:
```
+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]...
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.
```
+*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
+
+*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.
+
+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``.
+
-## The philosophy behind *Black*
+## The *Black* code style
*Black* reformats entire files in place. It is not configurable. It
doesn't take previous formatting into account. It doesn't reformat
@@ -59,24 +146,27 @@ recognizes [YAPF](https://github.com/google/yapf)'s block comments to
the same effect, as a courtesy for straddling code.
-### How *Black* formats files
+### How *Black* wraps lines
*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.
+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,
great.
```py3
# in:
+
l = [1,
2,
3,
]
# out:
+
l = [1, 2, 3]
```
@@ -84,12 +174,14 @@ If not, *Black* will look at the contents of the first outer matching
brackets and put that in a separate indented line.
```py3
# in:
-l = [[n for n in list_bosses()], [n for n in list_employees()]]
+
+TracebackException.from_exception(exc, limit, lookup_lines, capture_locals)
# out:
-l = [
- [n for n in list_bosses()], [n for n in list_employees()]
-]
+
+TracebackException.from_exception(
+ exc, limit, lookup_lines, capture_locals
+)
```
If that still doesn't fit the bill, it will decompose the internal
@@ -101,21 +193,22 @@ 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):
+
+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:
+ with open(file, "w") as f:
...
```
@@ -127,20 +220,30 @@ 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).
-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.
+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.
-*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.
+
+A compatible `.isort.cfg`
-That's it. The rest of the whitespace formatting rules follow PEP 8 and
-are designed to keep `pycodestyle` quiet.
+```
+[settings]
+multi_line_output=3
+include_trailing_comma=True
+force_grid_wrap=0
+combine_as_imports=True
+line_length=88
+```
+The equivalent command line is:
+```
+$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --combine-as --line-width=88 [ file.py ]
+```
+
### Line length
@@ -179,22 +282,589 @@ 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".
-### Editor integration
+### 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.
+
+*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
+
+*Black* will add trailing commas to expressions that are split
+by comma where each element is on its own line. This includes function
+signatures.
+
+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.
+
+### Numeric literals
+
+*Black* standardizes most numeric literals to use lowercase letters: `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`. In
+Python 3.6+, *Black* adds underscores to long numeric literals to aid
+readability: `100000000` becomes `100_000_000`.
+
+### 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)
+```
+
+
+### 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.
+
+
+### 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.
+
+
+Example `pyproject.toml`
+
+```toml
+[tool.black]
+line-length = 88
+py36 = true
+include = '\.pyi?$'
+exclude = '''
+/(
+ \.git
+ | \.hg
+ | \.mypy_cache
+ | \.tox
+ | \.venv
+ | _build
+ | buck-out
+ | build
+ | dist
+
+ # The following are specific to Black, you probably don't want those.
+ | blib2to3
+ | tests/data
+)/
+'''
+```
+
+
+
+### Lookup hierarchy
+
+Command-line options have defaults that you can see in `--help`.
+A `pyproject.toml` can override those defaults. Finally, options
+provided by the user on the command line override both.
+
+*Black* will only ever use one `pyproject.toml` file during an entire
+run. It doesn't look for multiple files, and doesn't compose
+configuration from different levels of the file hierarchy.
+
+
+## Editor integration
+
+### Emacs
+
+Use [proofit404/blacken](https://github.com/proofit404/blacken).
+
+
+### PyCharm
+
+1. Install `black`.
+
+```console
+$ pip install black
+```
+
+2. Locate your `black` installation folder.
-There is currently no integration with any text editors. Vim and
-Atom/Nuclide integration is planned by the author, others will require
-external contributions.
+ 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
+```
+
+3. Open External tools in PyCharm with `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:
+ - Arguments: `$FilePath$`
+
+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`.
+
+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 -> Tools -> File Watchers` and click `+` to add a new watcher:
+ - Name: Black
+ - File type: Python
+ - Scope: Project Files
+ - Program:
+ - 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',
+```
+
+or with [Vundle](https://github.com/VundleVim/Vundle.vim):
+
+```
+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.
+
+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.
+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 [python-black](https://atom.io/packages/python-black).
+
+
+### Other editors
+
+Other editors will require external contributions.
Patches welcome! ⨠ð° â¨
+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.
+
+This can be used for example with PyCharm'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.
+```
+
+### 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. If this value represents at least Python 3.6, `blackd` will
+ act as *Black* does when passed the `--py36` command line flag.
+
+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.
+
+## Version control integration
+
+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/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.
+
+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\\AppData\Local\black\black\Cache\\cache...pickle`
+* macOS: `/Users//Library/Caches/black//cache...pickle`
+* Linux: `/home//.cache/black//cache...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.
+
## 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!
@@ -209,25 +879,21 @@ and [`pipenv`](https://docs.pipenv.org/):
> This vastly improves the formatting of our code. Thanks a ton!
-## Tests
+## Show your style
-Just run:
+Use the badge in your project's README.md:
+```markdown
+[](https://github.com/ambv/black)
```
-python setup.py test
-```
-
-## This tool requires Python 3.6.0+ to run
-But you can reformat Python 2 code with it, too. *Black* is able to parse
-all of the new syntax supported on Python 3.6 but also *effectively all*
-the Python 2 syntax at the same time, as long as you're not using print
-statements.
+Using the badge in README.rst:
+```
+.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
+ :target: https://github.com/ambv/black
+```
-By making the code exclusively Python 3.6+, I'm able to focus on the
-quality of the formatting and re-use all the nice features of the new
-releases (check out [pathlib](docs.python.org/3/library/pathlib.html) or
-f-strings) instead of wasting cycles on Unicode compatibility, and so on.
+Looks like this: [](https://github.com/ambv/black)
## License
@@ -235,10 +901,10 @@ f-strings) instead of wasting cycles on Unicode compatibility, and so on.
MIT
-## Contributing
+## 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
@@ -248,9 +914,383 @@ 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
+### 18.9b0
+
+* numeric literals are now formatted by *Black* (#452, #461, #464, #469):
+
+ * numeric literals are normalized to include `_` separators on Python 3.6+ code
+
+ * code with `_` in numeric literals is recognized as Python 3.6+
+
+ * most letters in numeric literals are lowercased (e.g., in `1e10` or `0xab`)
+
+* added `blackd`, see [its documentation](#blackd) for more info (#349)
+
+* adjacent string literals are now correctly split into multiple lines (#463)
+
+* cache is now populated when `--check` is successful for a file which speeds up
+ consecutive checks of properly formatted unmodified files (#448)
+
+* code with `_` in numeric literals is recognized as Python 3.6+ (#461)
+
+* 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
+
+* 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 ð° Day 2018!
@@ -263,3 +1303,28 @@ You can still try but prepare to be disappointed.
## Authors
Glued together by [Åukasz 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),
+[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)
+* [Christian Heimes](mailto:christian@python.org)
+* [Daniel M. Capella](mailto:polycitizen@gmail.com)
+* [Eli Treuherz](mailto:eli@treuherz.com)
+* Hugo van Kemenade
+* [Ivan KataniÄ](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)