Run pyupgrade on blib2to3 and src (#3771)

[etc/vim.git] / docs / the_black_code_style / current_style.md

diff --git a/docs/the_black_code_style/current_style.md b/docs/the_black_code_style/current_style.md
index 0bf5894abdd6202d9298738f79d00c1b26e689d3..0fb59fe5aaed953d4472cea271cbf8882a50a34f 100644 (file)
--- a/docs/the_black_code_style/current_style.md
+++ b/docs/the_black_code_style/current_style.md
@@ -8,9 +8,10 @@ deliberately limited and rarely added. Previous formatting is taken into account
 little as possible, with rare exceptions like the magic trailing comma. The coding style
 used by _Black_ can be viewed as a strict subset of PEP 8.
 
 little as possible, with rare exceptions like the magic trailing comma. The coding style
 used by _Black_ can be viewed as a strict subset of PEP 8.
 

-_Black_ reformats entire files in place. It doesn't reformat blocks that start with
-`# fmt: off` and end with `# fmt: on`, or lines that ends with `# fmt: skip`.
-`# fmt: on/off` have to be on the same level of indentation. It also recognizes
+_Black_ reformats entire files in place. It doesn't reformat lines that end with
+`# fmt: skip` or blocks that start with `# fmt: off` and end with `# fmt: on`.
+`# fmt: on/off` must be on the same level of indentation and in the same block, meaning
+no unindents beyond the initial indentation level between them. It also recognizes

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


@@ -84,6 +85,19 @@ def very_important_function(
         ...
 ```
 
         ...
 ```
 

+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](../guides/using_black_with_other_tools.md#isort) with the ready-made `black`
+profile or manual configuration.
+
+You might have noticed that closing brackets are always dedented and that a trailing
+comma is always added. Such formatting produces smaller diffs; when you add or remove an
+element, it's always just one line. Also, having the closing bracket dedented provides a
+clear delimiter between two distinct sections of the code that otherwise share the same
+indentation level (like the arguments list and the docstring in the example above).
+

 (labels/why-no-backslashes)=
 
 _Black_ prefers parentheses over backslashes, and will remove backslashes if found.
 (labels/why-no-backslashes)=
 
 _Black_ prefers parentheses over backslashes, and will remove backslashes if found.


@@ -126,18 +140,7 @@ If you're reaching for backslashes, that's a clear signal that you can do better
 slightly refactor your code. I hope some of the examples above show you that there are
 many ways in which you can do it.
 
 slightly refactor your code. I hope some of the examples above show you that there are
 many ways in which you can do it.
 

-You might have noticed that closing brackets are always dedented and that a trailing
-comma is always added. Such formatting produces smaller diffs; when you add or remove an
-element, it's always just one line. Also, having the closing bracket dedented provides a
-clear delimiter between two distinct sections of the code that otherwise share the same
-indentation level (like the arguments list and the docstring in the example above).
-
-If a data structure literal (tuple, list, set, dict) or a line of "from" imports cannot
-fit in the allotted length, it's always split into one element per line. This minimizes
-diffs as well as enables readers of code to find which commit introduced a particular
-entry. This also makes _Black_ compatible with
-[isort](../guides/using_black_with_other_tools.md#isort) with the ready-made `black`
-profile or manual configuration.
+(labels/line-length)=

 
 ### Line length
 
 
 ### Line length
 


@@ -157,33 +160,35 @@ harder to work with line lengths exceeding 100 characters. It also adversely aff
 side-by-side diff review on typical screen resolutions. Long lines also make it harder
 to present code neatly in documentation or talk slides.
 
 side-by-side diff review on typical screen resolutions. Long lines also make it harder
 to present code neatly in documentation or talk slides.
 

-If you're using Flake8, you can bump `max-line-length` to 88 and mostly forget about it.
-However, it's better if you use [Bugbear](https://github.com/PyCQA/flake8-bugbear)'s
-B950 warning instead of E501, and bump the max line length to 88 (or the `--line-length`
-you used for black), which will align more with black's _"try to respect
-`--line-length`, but don't become crazy if you can't"_. You'd do it like this:
-
-```ini
-[flake8]
-max-line-length = 88
-...
-select = C,E,F,W,B,B950
-extend-ignore = E203, E501
-```
+#### Flake8

 
 

-Explanation of why E203 is disabled can be found further in this documentation. And 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".
+If you use Flake8, you have a few options:

 
 

-**If you're looking for a minimal, black-compatible flake8 configuration:**
+1. Recommended is using [Bugbear](https://github.com/PyCQA/flake8-bugbear) and enabling
+   its B950 check instead of using Flake8's E501, because it aligns with Black's 10%
+   rule. Install Bugbear and use the following config:

 
 

-```ini
-[flake8]
-max-line-length = 88
-extend-ignore = E203
-```
+   ```ini
+   [flake8]
+   max-line-length = 80
+   ...
+   select = C,E,F,W,B,B950
+   extend-ignore = E203, E501
+   ```
+
+   The rationale for E950 is explained in
+   [Bugbear's documentation](https://github.com/PyCQA/flake8-bugbear#opinionated-warnings).
+
+2. For a minimally compatible config:
+
+   ```ini
+   [flake8]
+   max-line-length = 88
+   extend-ignore = E203
+   ```
+
+An explanation of why E203 is disabled can be found in the [Slices section](#slices) of
+this page.

 
 ### Empty lines
 
 
 ### Empty lines
 


@@ -193,7 +198,45 @@ 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
 _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.
+space, this whitespace is lost. The other exception is that it will remove any empty
+lines immediately following a statement that introduces a new indentation level.
+
+```python
+# in:
+
+def foo():
+
+    print("All the newlines above me should be deleted!")
+
+
+if condition:
+
+    print("No newline above me!")
+
+    print("There is a newline above me, and that's OK!")
+
+
+class Point:
+
+    x: int
+    y: int
+
+# out:
+
+def foo():
+    print("All the newlines above me should be deleted!")
+
+
+if condition:
+    print("No newline above me!")
+
+    print("There is a newline above me, and that's OK!")
+
+
+class Point:
+    x: int
+    y: int
+```

 
 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
 
 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


@@ -234,6 +277,8 @@ A pre-existing trailing comma informs _Black_ to always explode contents of the
 bracket pair into one item per line. Read more about this in the
 [Pragmatism](#pragmatism) section below.
 
 bracket pair into one item per line. Read more about this in the
 [Pragmatism](#pragmatism) section below.
 

+(labels/strings)=
+

 ### Strings
 
 _Black_ prefers double quotes (`"` and `"""`) over single quotes (`'` and `'''`). It
 ### Strings
 
 _Black_ prefers double quotes (`"` and `"""`) over single quotes (`'` and `'''`). It


@@ -399,16 +444,16 @@ recommended code style for those files is more terse than PEP 8:
 _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:
 
 _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`;
 - 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
 - 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]`.
+  versions of Python.
+
+### Line endings
+
+_Black_ will normalize line endings (`\n` or `\r\n`) based on the first line ending of
+the file.

 
 ## Pragmatism
 
 
 ## Pragmatism
 


@@ -418,6 +463,8 @@ there were not many users anyway. Not many edge cases were reported. As a mature
 _Black_ does make some exceptions to rules it otherwise holds. This section documents
 what those exceptions are and why this is the case.
 
 _Black_ does make some exceptions to rules it otherwise holds. This section documents
 what those exceptions are and why this is the case.
 

+(labels/magic-trailing-comma)=
+

 ### The magic trailing comma
 
 _Black_ in general does not take existing formatting into account.
 ### The magic trailing comma
 
 _Black_ in general does not take existing formatting into account.


@@ -454,17 +501,19 @@ default by (among others) GitHub and Visual Studio Code, differentiates between
 r-strings and R-strings. The former are syntax highlighted as regular expressions while
 the latter are treated as true raw strings with no special semantics.
 
 r-strings and R-strings. The former are syntax highlighted as regular expressions while
 the latter are treated as true raw strings with no special semantics.
 

+(labels/ast-changes)=
+

 ### AST before and after formatting
 
 ### AST before and after formatting
 

-When run with `--safe`, _Black_ checks that the code before and after is semantically
-equivalent. This check is done by comparing the AST of the source with the AST of the
-target. There are three limited cases in which the AST does differ:
+When run with `--safe` (the default), _Black_ checks that the code before and after is
+semantically equivalent. This check is done by comparing the AST of the source with the
+AST of the target. There are three limited cases in which the AST does differ:

 
 1. _Black_ cleans up leading and trailing whitespace of docstrings, re-indenting them if
    needed. It's been one of the most popular user-reported features for the formatter to
    fix whitespace issues with docstrings. While the result is technically an AST
 
 1. _Black_ cleans up leading and trailing whitespace of docstrings, re-indenting them if
    needed. It's been one of the most popular user-reported features for the formatter to
    fix whitespace issues with docstrings. While the result is technically an AST

-   difference, due to the various possibilities of forming docstrings, all realtime use
-   of docstrings that we're aware of sanitizes indentation and leading/trailing
+   difference, due to the various possibilities of forming docstrings, all real-world
+   uses of docstrings that we're aware of sanitize indentation and leading/trailing

    whitespace anyway.
 
 1. _Black_ manages optional parentheses for some statements. In the case of the `del`
    whitespace anyway.
 
 1. _Black_ manages optional parentheses for some statements. In the case of the `del`