X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/6e97c5f47cbec72c72c27aefb206589dd84707a7..d4a85643a465f5fae2113d07d22d021d4af4795a:/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 1d1e42e..56b9252 100644 --- a/docs/the_black_code_style/current_style.md +++ b/docs/the_black_code_style/current_style.md @@ -2,11 +2,16 @@ ## Code style -_Black_ reformats entire files in place. Style configuration options are deliberately -limited and rarely added. It doesn't take previous formatting into account, except for -the magic trailing comma and preserving newlines. 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_ aims for consistency, generality, readability and reducing git diffs. Similar +language constructs are formatted with similar rules. Style configuration options are +deliberately limited and rarely added. Previous formatting is taken into account as +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 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. @@ -18,8 +23,7 @@ running `black --preview`. _Black_ ignores previous formatting and applies uniform horizontal and vertical whitespace to your code. The rules for horizontal whitespace can be summarized as: do -whatever makes `pycodestyle` happy. The coding style used by _Black_ can be viewed as a -strict subset of PEP 8. +whatever makes `pycodestyle` happy. As for vertical whitespace, _Black_ tries to render one full expression or simple statement per line. If this fits the allotted line length, great. @@ -81,6 +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. @@ -123,19 +140,6 @@ 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. -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. - ### Line length You probably noticed the peculiar default line length. _Black_ defaults to 88 characters @@ -284,6 +288,26 @@ multiple lines. This is so that _Black_ is compliant with the recent changes in [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. +Almost all operators will be surrounded by single spaces, the only exceptions are unary +operators (`+`, `-`, and `~`), and power operators when both operands are simple. For +powers, an operand is considered simple if it's only a NAME, numeric CONSTANT, or +attribute access (chained attribute access is allowed), with or without a preceding +unary operator. + +```python +# For example, these won't be surrounded by whitespace +a = x**y +b = config.base**5.2 +c = config.base**runtime.config.exponent +d = 2**5 +e = 2**~5 + +# ... but these will be surrounded by whitespace +f = 2 ** get_exponent() +g = get_x() ** get_y() +h = config['base'] ** 2 +``` + ### Slices PEP 8 @@ -376,16 +400,16 @@ 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: -- 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]`. + versions of Python. + +### Line endings + +_Black_ will normalize line endings (`\n` or `\r\n`) based on the first line ending of +the file. ## Pragmatism @@ -433,15 +457,15 @@ the latter are treated as true raw strings with no special semantics. ### 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 - 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`