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Fix formatter instability with half-indented comment (#6460)

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## Summary
The bug was happening in this
[loop](75f402eb82/crates/ruff_python_formatter/src/comments/placement.rs (L545)).

Basically, In the first iteration of the loop, the `comment_indentation`
is bigger than `child_indentation` (`comment_indentation` is 7 and
`child_indentation` is 4) making the `Ordering::Greater` branch execute.
Inside the `Ordering::Greater` branch, the `if` block gets executed,
resulting in the update of these variables.
```rust
parent_body = current_body;                    
current_body = Some(last_child_in_current_body);
last_child_in_current_body = nested_child;
```
In the second iteration of the loop, `comment_indentation` is smaller
than `child_indentation` (`comment_indentation` is 7 and
`child_indentation` is 8) making the `Ordering::Less` branch execute.
Inside the `Ordering::Less` branch, the `if` block gets executed, this
is where the bug was happening. At this point `parent_body` should be a
`StmtFunctionDef` but it was a `StmtClassDef`. Causing the comment to be
incorrectly formatted.

That happened for the following code:
```python
class A:
    def f():
        pass
       # strangely indented comment

print()
```

There is only one problem that I couldn't figure it out a solution, the
variable `current_body` in this
[line](75f402eb82/crates/ruff_python_formatter/src/comments/placement.rs (L542C5-L542C49))
now gives this warning _"value assigned to `current_body` is never read
maybe it is overwritten before being read?"_
Any tips on how to solve that?

Closes #5337

## Test Plan

Add new test case.

---------

Co-authored-by: konstin <konstin@mailbox.org>
This commit is contained in:
Victor Hugo Gomes 2023-08-11 08:21:16 -03:00 • committed by GitHub
parent 0ef6af807b
commit b05574babd
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GPG key ID: 4AEE18F83AFDEB23
5 changed files with 79 additions and 26 deletions
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35
crates/ruff_python_formatter/src/comments/placement.rs
View file

@ -451,12 +451,11 @@ fn handle_own_line_comment_after_branch<'a>(
return CommentPlacement::Default(comment);
}
let mut parent_body = None;
let mut current_body = Some(preceding_node);
let mut last_child_in_current_body = last_child;
let mut parent = None;
let mut last_child_in_parent = last_child;
loop {
let child_indentation = indentation(locator, &last_child_in_current_body)
let child_indentation = indentation(locator, &last_child_in_parent)
.unwrap_or_default()
.len();
@ -465,15 +464,16 @@ fn handle_own_line_comment_after_branch<'a>(
// if parent_body:
// if current_body:
// child_in_body()
// last_child_in_current_body # may or may not have children on its own
// last_child_in_current_body # may or may not have children on its own
// # less: Comment belongs to the parent block.
// # less
// # less: Comment belongs to the parent block.
// # equal: The comment belongs to this block.
// # greater
// # greater: The comment belongs to the inner block.
// # greater (but less in the next iteration)
// # greater: The comment belongs to the inner block.
// ```
match comment_indentation.cmp(&child_indentation) {
Ordering::Less => {
return if let Some(parent_block) = parent_body {
return if let Some(parent_block) = parent {
// Comment belongs to the parent block.
CommentPlacement::trailing(parent_block, comment)
} else {
@ -488,14 +488,13 @@ fn handle_own_line_comment_after_branch<'a>(
}
Ordering::Equal => {
// The comment belongs to this block.
return CommentPlacement::trailing(last_child_in_current_body, comment);
return CommentPlacement::trailing(last_child_in_parent, comment);
}
Ordering::Greater => {
if let Some(nested_child) = last_child_in_body(last_child_in_current_body) {
if let Some(nested_child) = last_child_in_body(last_child_in_parent) {
// The comment belongs to the inner block.
parent_body = current_body;
current_body = Some(last_child_in_current_body);
last_child_in_current_body = nested_child;
parent = Some(last_child_in_parent);
last_child_in_parent = nested_child;
} else {
// The comment is overindented, we assign it to the most indented child we have.
// ```python
@ -503,7 +502,7 @@ fn handle_own_line_comment_after_branch<'a>(
// pass
// # comment
// ```
return CommentPlacement::trailing(last_child_in_current_body, comment);
return CommentPlacement::trailing(last_child_in_parent, comment);
}
}
}
@ -1346,7 +1345,7 @@ where
right.is_some_and(|right| left.ptr_eq(right.into()))
}
/// The last child of the last branch, if the node hs multiple branches.
/// The last child of the last branch, if the node has multiple branches.
fn last_child_in_body(node: AnyNodeRef) -> Option<AnyNodeRef> {
let body = match node {
AnyNodeRef::StmtFunctionDef(ast::StmtFunctionDef { body, .. })
@ -1504,9 +1503,7 @@ mod tests {
);
assert_eq!(
max_empty_lines(
"# trailing comment\n\n# own line comment\n\n\n# an other own line comment\n# block"
),
max_empty_lines("# trailing comment\n\n# own line comment\n\n\n# an other own line comment\n# block"),
2
);