## Summary
This is small refactoring to reuse the code that detects the magic
trailing comma across functions. I make this change now to avoid copying
code in a later PR. @MichaReiser is planning on making a larger
refactoring later that integrates with the join nodes builder
## Test Plan
No functional changes. The magic trailing comma behaviour is checked by
the fixtures.
## Motivation
While black keeps parentheses nearly everywhere, the notable exception
is in the body of for loops:
```python
for (a, b) in x:
pass
```
becomes
```python
for a, b in x:
pass
```
This currently blocks #5163, which this PR should unblock.
## Solution
This changes the `ExprTuple` formatting option to include one additional
option that removes the parentheses when not using magic trailing comma
and not breaking. It is supposed to be used through
```rust
#[derive(Debug)]
struct ExprTupleWithoutParentheses<'a>(&'a Expr);
impl Format<PyFormatContext<'_>> for ExprTupleWithoutParentheses<'_> {
fn fmt(&self, f: &mut Formatter<PyFormatContext<'_>>) -> FormatResult<()> {
match self.0 {
Expr::Tuple(expr_tuple) => expr_tuple
.format()
.with_options(TupleParentheses::StripInsideForLoop)
.fmt(f),
other => other.format().with_options(Parenthesize::IfBreaks).fmt(f),
}
}
}
```
## Testing
The for loop formatting isn't merged due to missing this (and i didn't
want to create more git weirdness across two people), but I've confirmed
that when applying this to while loops instead of for loops, then
```rust
write!(
f,
[
text("while"),
space(),
ExprTupleWithoutParentheses(test.as_ref()),
text(":"),
trailing_comments(trailing_condition_comments),
block_indent(&body.format())
]
)?;
```
makes
```python
while (a, b):
pass
while (
ajssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssa,
b,
):
pass
while (a,b,):
pass
```
formatted as
```python
while a, b:
pass
while (
ajssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssa,
b,
):
pass
while (
a,
b,
):
pass
```
This implements formatting ExprTuple, including magic trailing comma. I
intentionally didn't change the settings mechanism but just added a
dummy global const flag.
Besides the snapshots, I added custom breaking/joining tests and a
deeply nested test case. The diffs look better than previously, proper
black compatibility depends on parentheses handling.
---------
Co-authored-by: Micha Reiser <micha@reiser.io>
* A basic StmtAssign formatter and better dummies for expressions
The goal of this PR was formatting StmtAssign since many nodes in the black tests (and in python in general) are after an assignment. This caused unstable formatting: The spacing of power op spacing depends on the type of the two involved expressions, but each expression was formatted as dummy string and re-parsed as a ExprName, so in the second round the different rules of ExprName were applied, causing unstable formatting.
This PR does not necessarily bring us closer to black's style, but it unlocks a good porting of black's test suite and is a basis for implementing the Expr nodes.
* fmt
* Review
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## Summary
This PR replaces the `verbatim_text` builder with a `not_yet_implemented` builder that emits `NOT_YET_IMPLEMENTED_<NodeKind>` for not yet implemented nodes.
The motivation for this change is that partially formatting compound statements can result in incorrectly indented code, which is a syntax error:
```python
def func_no_args():
a; b; c
if True: raise RuntimeError
if False: ...
for i in range(10):
print(i)
continue
```
Get's reformatted to
```python
def func_no_args():
a; b; c
if True: raise RuntimeError
if False: ...
for i in range(10):
print(i)
continue
```
because our formatter does not yet support `for` statements and just inserts the text from the source.
## Downsides
Using an identifier will not work in all situations. For example, an identifier is invalid in an `Arguments ` position. That's why I kept `verbatim_text` around and e.g. use it in the `Arguments` formatting logic where incorrect indentations are impossible (to my knowledge). Meaning, `verbatim_text` we can opt in to `verbatim_text` when we want to iterate quickly on nodes that we don't want to provide a full implementation yet and using an identifier would be invalid.
## Upsides
Running this on main discovered stability issues with the newline handling that were previously "hidden" because of the verbatim formatting. I guess that's an upside :)
## Test Plan
None?
Charlie Marsh
Micha Reiser
konstin