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compiletest: ignore SVG y offset in by-lines comparison #157350

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compiletest: ignore SVG y offset in by-lines comparison #157350

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36 changes: 31 additions & 5 deletions src/tools/compiletest/src/runtest.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2714,11 +2714,37 @@ impl<'test> TestCx<'test> {
(&tmp.0, &tmp.1)
}
} else if compare_output_by_lines {
let mut actual_lines: Vec<&str> = actual.lines().collect();
let mut expected_lines: Vec<&str> = expected.lines().collect();
actual_lines.sort_unstable();
expected_lines.sort_unstable();
if actual_lines == expected_lines {
// SVG output (`--color=always`) renders one terminal row per line,
// laid out top to bottom. Under the parallel front-end, independent
// diagnostics can be emitted in a different order, which permutes the
// rows and re-renders each at a different vertical `y` offset without
// changing its content. Strip the `y` coordinate (and the first line,
// the `<svg>` header whose width/height are already ignored by the
// exact comparison above) before the line-multiset comparison so that
// such a reordering is not reported as a difference. The normalization
// is comparison-only: on mismatch the original strings are kept for
// the diff and for blessing. Single-threaded runs take the
// exact-comparison path above and still check `y`.
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@petrochenkov petrochenkov Jun 3, 2026 •
edited by rustbot
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@zetanumbers
At least the root cause analyses look plausible (although they need to be verified by a human of course), and may be potentially put into the tracking issue, even if the change is not merged.

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@xmakro xmakro Jun 4, 2026 •
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When running the SVG test under the parallel frontend at head, then any run fails the existing line by line comparison, and compiletest writes the actual rendered SVG to disk:

RS=tests/ui/error-emitter/multiline-removal-suggestion.rs
for i in $(seq 1 40); do
  ./x test $RS --test-args "--parallel-frontend-threads=16" --force-rerun
done
# each failing run prints: Saved the actual svg to `<build>/.../multiline-removal-suggestion.svg`

Both files are 456 lines, but the diagnostic blocks come out in a different vertical order:

A: E0277@21:8 E0277@53:28 E0277@43:7 E0277@32:6 E0277@50:2 E0277@39:2 ...
B: E0277@43:7 E0277@39:2 E0277@53:28 E0277@32:6 E0277@21:8 E0277@50:2 ...

Raw sorted line comparison, which is what the test does before this PR:

$ diff <(sort A.svg) <(sort B.svg) | grep -c '^[<>]'
232      # nonzero, so the comparison reports a difference

By comparison, with this PR, we drop the <svg> header line, replace y="..px" with a constant, then sort:

$ norm(){ tail -n +2 "$1" | sed -E 's/y="[0-9]+px"/y="0px"/g' | sort; }
$ diff <(norm A.svg) <(norm B.svg) | grep -c '^[<>]'
0        # identical as a multiset

Each differing line is the same row at a different height. For example the rows for the span at :39:2:

A: <tspan x="10px" y="1648px"> ... rs:39:2</tspan>
B: <tspan x="10px" y="370px"> ... rs:39:2</tspan>

The content is the same but the y changes. After the substitution both become y="0px" and match.

let matches = if self.force_color_svg() {
let strip_y = static_regex!(r#"y="\d+px""#);
let normalize = |svg: &str| {
let mut lines: Vec<String> = svg
.lines()
.skip(1)
.map(|line| strip_y.replace_all(line, r#"y="0px""#).into_owned())
.collect();
lines.sort_unstable();
lines
};
normalize(expected) == normalize(actual)
} else {
let mut actual_lines: Vec<&str> = actual.lines().collect();
let mut expected_lines: Vec<&str> = expected.lines().collect();
actual_lines.sort_unstable();
expected_lines.sort_unstable();
actual_lines == expected_lines
};
if matches {
return CompareOutcome::Same;
} else {
(expected, actual)
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1 change: 0 additions & 1 deletion tests/ui/error-emitter/multiline-removal-suggestion.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,4 +56,3 @@ fn bay() -> Vec<(bool, HashSet<u8>)> {
.collect()
}
fn main() {}
//@ ignore-parallel-frontend invalid svg(multiple threads trying to write to the same file)
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