In ruff-lsp (https://github.com/charliermarsh/ruff-lsp/pull/76) we want to add a "Disable \<rule\> for this line" quickfix. However, finding the correct line into which the `noqa` comment should be inserted is non-trivial (multi-line strings for example).
Ruff already has this info, so expose it in the JSON output for use by ruff-lsp.
For example:
$ ruff check --select=EM<Tab>
EM -- flake8-errmsg
EM10 EM1 --
EM101 -- raw-string-in-exception
EM102 -- f-string-in-exception
EM103 -- dot-format-in-exception
(You will need to enable autocompletion as described
in the Autocompletion section in the README.)
Fixes#2808.
(The --help help change in the README is due to a clap bug,
for which I already submitted a fix:
https://github.com/clap-rs/clap/pull/4710.)
# Summary
This PR contains the code for the autoformatter proof-of-concept.
## Crate structure
The primary formatting hook is the `fmt` function in `crates/ruff_python_formatter/src/lib.rs`.
The current formatter approach is outlined in `crates/ruff_python_formatter/src/lib.rs`, and is structured as follows:
- Tokenize the code using the RustPython lexer.
- In `crates/ruff_python_formatter/src/trivia.rs`, extract a variety of trivia tokens from the token stream. These include comments, trailing commas, and empty lines.
- Generate the AST via the RustPython parser.
- In `crates/ruff_python_formatter/src/cst.rs`, convert the AST to a CST structure. As of now, the CST is nearly identical to the AST, except that every node gets a `trivia` vector. But we might want to modify it further.
- In `crates/ruff_python_formatter/src/attachment.rs`, attach each trivia token to the corresponding CST node. The logic for this is mostly in `decorate_trivia` and is ported almost directly from Prettier (given each token, find its preceding, following, and enclosing nodes, then attach the token to the appropriate node in a second pass).
- In `crates/ruff_python_formatter/src/newlines.rs`, normalize newlines to match Black’s preferences. This involves traversing the CST and inserting or removing `TriviaToken` values as we go.
- Call `format!` on the CST, which delegates to type-specific formatter implementations (e.g., `crates/ruff_python_formatter/src/format/stmt.rs` for `Stmt` nodes, and similar for `Expr` nodes; the others are trivial). Those type-specific implementations delegate to kind-specific functions (e.g., `format_func_def`).
## Testing and iteration
The formatter is being developed against the Black test suite, which was copied over in-full to `crates/ruff_python_formatter/resources/test/fixtures/black`.
The Black fixtures had to be modified to create `[insta](https://github.com/mitsuhiko/insta)`-compatible snapshots, which now exist in the repo.
My approach thus far has been to try and improve coverage by tackling fixtures one-by-one.
## What works, and what doesn’t
- *Most* nodes are supported at a basic level (though there are a few stragglers at time of writing, like `StmtKind::Try`).
- Newlines are properly preserved in most cases.
- Magic trailing commas are properly preserved in some (but not all) cases.
- Trivial leading and trailing standalone comments mostly work (although maybe not at the end of a file).
- Inline comments, and comments within expressions, often don’t work -- they work in a few cases, but it’s one-off right now. (We’re probably associating them with the “right” nodes more often than we are actually rendering them in the right place.)
- We don’t properly normalize string quotes. (At present, we just repeat any constants verbatim.)
- We’re mishandling a bunch of wrapping cases (if we treat Black as the reference implementation). Here are a few examples (demonstrating Black's stable behavior):
```py
# In some cases, if the end expression is "self-closing" (functions,
# lists, dictionaries, sets, subscript accesses, and any length-two
# boolean operations that end in these elments), Black
# will wrap like this...
if some_expression and f(
b,
c,
d,
):
pass
# ...whereas we do this:
if (
some_expression
and f(
b,
c,
d,
)
):
pass
# If function arguments can fit on a single line, then Black will
# format them like this, rather than exploding them vertically.
if f(
a, b, c, d, e, f, g, ...
):
pass
```
- We don’t properly preserve parentheses in all cases. Black preserves parentheses in some but not all cases.
Rule::noqa_code previously return a single &'static str,
which was possible because we had one enum listing all
rule code prefixes. This commit series will however split up
the RuleCodePrefix enum into several enums ... so we'll end up
with two &'static str ... this commit wraps the return type
of Rule::noqa_code into a newtype so that we can easily change
it to return two &'static str in the 6th commit of this series.
Post this commit series several codes can be mapped to a single rule,
this commit therefore renames Rule::code to Rule::noqa_code,
which is the code that --add-noqa will add to ignore a rule.
This is causing wheel creation to fail on some of our more exotic build targets: 4159524132.
Let's figure out how to gate appropriately, but for now, reverting to get the release out.
The synopsis is as follows.
List all top-level config keys:
$ ruff config
allowed-confusables
builtins
cache-dir
... etc.
List all config keys in a specific section:
$ ruff config mccabe
max-complexity
Describe a specific config option:
$ ruff config mccabe.max-complexity
The maximum McCabe complexity to allow before triggering `C901` errors.
Default value: 10
Type: int
Example usage:
```toml
# Flag errors (`C901`) whenever the complexity level exceeds 5.
max-complexity = 5
```
The new `ruff rule` output format introduced in
551b810aeb doesn't print Markdown but
rather some rich text with escape sequences for colors and links,
it's actually the "text" format that prints Markdown, so naming the new
format "markdown" is very confusing. This commit therefore renames it to
"pretty".
This isn't a breaking change since there hasn't been a release yet.
