Test on Python 3.8 final (#1070)

[etc/vim.git] / README.md

diff --git a/README.md b/README.md
index 96a24a1eb4ac1d63534ebf8a9cec06d45599a15a..76ae9cfee788c5746e06db7bf57d8e9d37493397 100644 (file)
--- a/README.md
+++ b/README.md
@@ -1,14 +1,14 @@
-![Black Logo](https://raw.githubusercontent.com/ambv/black/master/docs/_static/logo2-readme.png)
+![Black Logo](https://raw.githubusercontent.com/psf/black/master/docs/_static/logo2-readme.png)

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

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

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

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


@@ -28,6 +28,7 @@ content instead.
 possible.
 
 Try it out now using the [Black Playground](https://black.now.sh).
 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.

 
 ---
 
 
 ---
 


@@ -35,8 +36,10 @@ Try it out now using the [Black Playground](https://black.now.sh).
 **[Code style](#the-black-code-style)** |
 **[pyproject.toml](#pyprojecttoml)** |
 **[Editor integration](#editor-integration)** |
 **[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)** |
 **[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)** |
 **[Testimonials](#testimonials)** |
 **[Show your style](#show-your-style)** |
 **[Contributing](#contributing-to-black)** |


@@ -70,44 +73,59 @@ black {source_file_or_directory}
 black [OPTIONS] [SRC]...
 
 Options:
 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).
+  -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
   -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.
+                                  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:


@@ -121,7 +139,7 @@ Options:
 
 ### NOTE: This is a beta product
 
 
 ### NOTE: This is a beta product
 

-*Black* is already successfully used by several projects, small and big.
+*Black* is already [successfully used](#used-by) by many projects, small and big.

 It also sports a decent test suite.  However, it is still very new.
 Things will probably be wonky for a while. This is made explicit by the
 "Beta" trove classifier, as well as by the "b" in the version number.
 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.


@@ -140,7 +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.
 


@@ -159,14 +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


@@ -174,12 +193,12 @@ brackets and put that in a separate indented line.
 ```py3
 # in:
 
 ```py3
 # in:
 

-TracebackException.from_exception(exc, limit, lookup_lines, capture_locals)
+ImportantClass.important_method(exc, limit, lookup_lines, capture_locals, extra_argument)

 
 # out:
 
 
 # out:
 

-TracebackException.from_exception(
-    exc, limit, lookup_lines, capture_locals
+ImportantClass.important_method(
+    exc, limit, lookup_lines, capture_locals, extra_argument

 )
 ```
 
 )
 ```
 


@@ -193,7 +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:
         ...


@@ -204,6 +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`."""


@@ -234,13 +255,13 @@ the following configuration.
 multi_line_output=3
 include_trailing_comma=True
 force_grid_wrap=0
 multi_line_output=3
 include_trailing_comma=True
 force_grid_wrap=0

-combine_as_imports=True
+use_parentheses=True

 line_length=88
 ```
 
 The equivalent command line is:
 ```
 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 ]
+$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --use-parentheses --line-width=88 [ file.py ]

 ```
 </details>
 
 ```
 </details>
 


@@ -272,11 +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".
 


@@ -351,11 +373,11 @@ 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
 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.


@@ -371,6 +393,13 @@ 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.
 
 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
 
 
 ### Line breaks & binary operators
 


@@ -530,6 +559,8 @@ other file.
 If you're running with `--verbose`, you will see a blue message if
 a file was found and used.
 
 If you're running with `--verbose`, you will see a blue message if
 a file was found and used.
 

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

 
 ### Configuration format
 
 
 ### Configuration format
 


@@ -549,24 +580,26 @@ to denote a significant space character.
 ```toml
 [tool.black]
 line-length = 88
 ```toml
 [tool.black]
 line-length = 88

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

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

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

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


@@ -587,10 +620,11 @@ configuration from different levels of the file hierarchy.
 
 ### Emacs
 
 
 ### 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`.
 


@@ -614,28 +648,69 @@ $ where black
 %LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe  # possible location
 ```
 
 %LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe  # possible location
 ```
 

-3. Open External tools in PyCharm with `File -> Settings -> Tools -> External Tools`.
+3. Open External tools in PyCharm/IntelliJ IDEA
+
+  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 -> External Tools -> External Tools - Black`.
+    - 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:
+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.
 
     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:
+    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: `$FilePath$`
         - Name: Black
         - File type: Python
         - Scope: Project Files
         - Program: <install_location_from_step_2>
         - Arguments: `$FilePath$`

-        - Output paths to refresh: `$FilePathRelativeToProjectRoot$`
+        - Output paths to refresh: `$FilePath$`

         - Working directory: `$ProjectFileDir$`
         - 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
 
 
 ### Vim
 


@@ -655,16 +730,16 @@ Configuration:
 To install with [vim-plug](https://github.com/junegunn/vim-plug):
 
 ```
 To install with [vim-plug](https://github.com/junegunn/vim-plug):
 
 ```

-Plug 'ambv/black',
+Plug 'psf/black'

 ```
 
 or with [Vundle](https://github.com/VundleVim/Vundle.vim):
 
 ```
 ```
 
 or with [Vundle](https://github.com/VundleVim/Vundle.vim):
 
 ```

-Plugin 'ambv/black'
+Plugin 'psf/black'

 ```
 
 ```
 

-or you can copy the plugin from [plugin/black.vim](https://github.com/ambv/black/tree/master/plugin/black.vim).
+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
 `packadd`, or Pathogen, and so on.
 
 Let me know if this requires any changes to work with Vim 8's builtin
 `packadd`, or Pathogen, and so on.
 


@@ -706,7 +781,7 @@ Use the [Python extension](https://marketplace.visualstudio.com/items?itemName=m
 Use [sublack plugin](https://github.com/jgirardet/sublack).
 
 
 Use [sublack plugin](https://github.com/jgirardet/sublack).
 
 

-### IPython Notebook Magic
+### Jupyter Notebook Magic

 
 Use [blackcellmagic](https://github.com/csurfer/blackcellmagic).
 
 
 Use [blackcellmagic](https://github.com/csurfer/blackcellmagic).
 


@@ -721,7 +796,7 @@ the [Python Language Server](https://github.com/palantir/python-language-server)
 
 ### Atom/Nuclide
 
 
 ### Atom/Nuclide
 

-Use [atom-black](https://github.com/hauntsaninja/atom-black).
+Use [python-black](https://atom.io/packages/python-black).

 
 
 ### Other editors
 
 
 ### Other editors


@@ -736,8 +811,90 @@ 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.
 
 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
 


@@ -746,7 +903,7 @@ 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


@@ -756,7 +913,7 @@ 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
 
 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`
+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`
 for an example.
 
 If you're already using Python 3.7, switch the `language_version`


@@ -779,6 +936,20 @@ is:
 `file-mode` is an int flag that determines whether the file was formatted as 3.6+ only,
 as .pyi, and whether string normalization was omitted.
 
 `file-mode` is an int flag that determines whether the file was formatted as 3.6+ only,
 as .pyi, and whether string normalization was omitted.
 

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

 
 ## Testimonials
 
 
 ## Testimonials
 


@@ -786,7 +957,7 @@ as .pyi, and whether string normalization was omitted.
 
 > *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!


@@ -806,16 +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
 ```
 
 Using the badge in README.rst:
 ```
 .. image:: https://img.shields.io/badge/code%20style-black-000000.svg

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

 ```
 
 ```
 

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

 
 
 ## License
 
 
 ## License


@@ -841,18 +1012,118 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
 
 ## Change Log
 
 
 ## Change Log
 

-### 18.8b0
+### 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)

 
 

-* numeric literals are now normalized to include `_` separators on Python 3.6+ code
-  (#452)
+* 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)
 
 
 * 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 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)
 
 * note: the Vim plugin stopped registering ``,=`` as a default chord as it turned out
   to be a bad idea (#415)
 


@@ -1216,18 +1487,23 @@ Maintained with [Carol Willing](mailto:carolcode@willingconsulting.com),
 Multiple contributions by:
 * [Anthony Sottile](mailto:asottile@umich.edu)
 * [Artem Malyshev](mailto:proofit404@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)
 * [Christian Heimes](mailto:christian@python.org)
 * [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)
 * [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)
+* [Neraste](mailto: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)
 * [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)
 * [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com)

+* [Chuck Wooters](mailto:chuck.wooters@microsoft.com)