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## Summary
And more custom logic around comments in bodies... uff.
Let's say we have the following code
```python
if x == y:
pass # trailing comment of pass
else: # trailing comment of `else`
print("I have no comments")
```
Right now, the formatter attaches the `# trailing comment of `else` as a trailing comment of `pass` because it doesn't "see" that there's an `else` keyword in between (because the else body is just a Vec and not a node).
This PR adds custom logic that attaches the trailing comments after the `else` as dangling comments to the `if` statement. The if statement must then split the dangling comments by `comments.text_position()`:
* All comments up to the first end-of-line comment are leading comments of the `else` keyword.
* All end-of-line comments coming after are `trailing` comments for the `else` keyword.
## Test Plan
I added new unit tests.
### Summary
This PR adds custom logic to handle end-of-line comments of the last statement in a body.
For example:
```python
while True:
if something.changed:
do.stuff() # trailing comment
b
```
The `# trailing comment` is a trailing comment of the `do.stuff()` expression statement. We incorrectly attached the comment as a trailing comment of the enclosing `while` statement because the comment is between the end of the while statement (the `while` statement ends right after `do.stuff()`) and before the `b` statement.
This PR fixes the placement to correctly attach these comments to the last statement in a body (recursively).
## Test Plan
I reviewed the snapshots and they now look correct. This may appear odd because a lot comments have now disappeared. This is the expected result because we use `verbatim` formatting for the block statements (like `while`) and that means that it only formats the inner content of the block, but not any trailing comments. The comments were visible before, because they were associated with the block statement (e.g. `while`).
* Add Format for Stmt
* Implement basic module formatting
This implements formatting each statement in a module with a hard line break in between, so that we can start formatting statements.
Basic testing is done by the snapshots
* Use dummy verbatim formatter for all nodes
* Use new formatter infrastructure in CLI and test
* Expose the new formatter in the CLI
* Merge import blocks
# Summary
We need to support CR line endings (as opposed to LF and CRLF line endings, which are already supported). They're rare, but they do appear in Python code, and we tend to panic on any file that uses them.
Our `Locator` abstraction now supports CR line endings. However, Rust's `str#lines` implementation does _not_.
This PR adds a `UniversalNewlineIterator` implementation that respects all of CR, LF, and CRLF line endings, and plugs it into most of the `.lines()` call sites.
As an alternative design, it could be nice if we could leverage `Locator` for this. We've already computed all of the line endings, so we could probably iterate much more efficiently?
# Test Plan
Largely relying on automated testing, however, also ran over some known failure cases, like #3404.
In hindsight, `ruff_python` is too general. A good giveaway is that it's actually a prefix of some other crates. The intent of this crate is to reimplement pieces of the Python standard library and CPython itself, so `ruff_python_stdlib` feels appropriate.
This PR enables us to apply the proper quotation marks, including support for escapes. There are some significant TODOs, especially around implicit concatenations like:
```py
(
"abc"
"def"
)
```
Which are represented as a single AST node, which requires us to tokenize _within_ the formatter to identify all the individual string parts.
I manually changed these in #3080 and #3083 to get the tests passing (with notes around the deviations) -- but that's no longer necessary, now that we have proper testing that takes deviations into account.
This just re-formats all the `.py.expect` files with Black, both to add a trailing newline and be doubly-certain that they're correctly formatted.
I also ensured that we add a hard line break after each statement, and that we avoid including an extra newline in the generated Markdown (since the code should contain the exact expected newlines).
This PR changes the testing infrastructure to run all black tests and:
* Pass if Ruff and Black generate the same formatting
* Fail and write a markdown snapshot that shows the input code, the differences between Black and Ruff, Ruffs output, and Blacks output
This is achieved by introducing a new `fixture` macro (open to better name suggestions) that "duplicates" the attributed test for every file that matches the specified glob pattern. Creating a new test for each file over having a test that iterates over all files has the advantage that you can run a single test, and that test failures indicate which case is failing.
The `fixture` macro also makes it straightforward to e.g. setup our own spec tests that test very specific formatting by creating a new folder and use insta to assert the formatted output.
# 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.
Micha Reiser
konstin
Charlie Marsh
Jeong, YunWon
Jonathan Plasse
Calum Young
Micha Reiser