| Issue |
182274
|
| Summary |
[clang-format] BeforeLambdaBody causes incorrect argument wrapping when lambda is not the last argument
|
| Labels |
clang-format
|
| Assignees |
|
| Reporter |
christophe-calmejane
|
## Description
When `BraceWrapping.BeforeLambdaBody` is `true` and a function call contains a lambda that is **not the last argument** (either followed by more arguments, or when multiple lambdas are present), arguments before the lambda are incorrectly wrapped to a new line even though they fit on the first line.
## Steps to Reproduce
Use the following `.clang-format` configuration:
```yaml
BasedOnStyle: LLVM
BreakBeforeBraces: Custom
BraceWrapping:
BeforeLambdaBody: true
AllowShortLambdasOnASingleLine: None
```
Format the following code:
```cpp
void test() {
func(a, b, [](int x) { return x; }, c);
}
```
## Expected Output
```cpp
void test() {
func(a, b,
[](int x)
{
return x;
},
c);
}
```
Arguments `a, b,` should stay on the same line as the function name.
## Actual Output
```cpp
void test() {
func(
a, b,
[](int x)
{
return x;
},
c);
}
```
Arguments `a, b,` are incorrectly wrapped to a new line, with a line break inserted right after the opening `(`.
## Root Cause
The `DisallowLineBreaks` heuristic in `ContinuationIndenter::addTokenOnCurrentLine` scans ahead for lambda braces and sets `State.NoLineBreak = true` when found. This heuristic is designed for inlined lambda bodies: when all arguments including the lambda should stay on the same line. However, with `BeforeLambdaBody`, the lambda body is intentionally expanded using Allman-style braces, so this heuristic should not apply — the multi-line lambda body is expected and should not trigger argument wrapping.
The issue manifests when:
- A lambda argument is followed by another argument (trailing argument after lambda)
- Multiple lambda arguments are present in the same function call
## Fix
Return `false` from the `DisallowLineBreaks` lambda when `BraceWrapping.BeforeLambdaBody` is `true`, since Allman-style lambda formatting makes the heuristic counterproductive. I can provide a PR with fix + unit tests.
## Environment
- LLVM version: 21.1.8 (and likely older versions since `BeforeLambdaBody` was introduced)
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