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GeezerVison is showing github.com — diff: place -y gutter marker at the middle of the gutter by nagendramohan · Pull Request #277 · uutils/diffutils

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@nagendramohan

@nagendramohan nagendramohan commented Aug 24, 2026

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In side-by-side (-y) output the gutter marker was written wherever process_half_line stopped
padding the left half (one column past sdiff_half_width), not at separator_pos (the middle of
the gutter). Those agree only when the gutter is 3–4 columns wide, so the default
--width=130 --tabsize=8 (gutter 3) looked right while other widths/tab sizes drifted — e.g.
--width=40 placed < at column 17 instead of 19.

Pad from half_width + 1 up to separator_pos before writing the marker so it lands at the gutter
middle, matching GNU sdiff. format_tabs_and_spaces is a no-op when already at/past separator_pos,
so narrow gutters are unaffected. Added a regression test at --width=40.

Fixes #269.

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@nagendramohan
diff: place -y gutter marker at the middle of the gutter
7d3f389 
In side-by-side output the gutter marker was written wherever
process_half_line stopped padding the left half (one column past
sdiff_half_width), not at separator_pos (the middle of the gutter).
Those agree only when the gutter is 3 or 4 columns wide, so the default
--width=130 --tabsize=8 (gutter 3) looked right while other widths/tab
sizes drifted (e.g. --width=40 placed '<' at column 17 instead of 19).

Pad from half_width + 1 up to separator_pos before writing the marker so
it lands at the gutter middle, matching GNU sdiff. format_tabs_and_spaces
is a no-op when already at/past separator_pos, so narrow gutters are
unaffected. Add a regression test at --width=40.

Fixes uutils#269
@github-actions

github-actions Bot commented Aug 24, 2026

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GNU diffutils testsuite comparison:

Test results comparison:
  Current:   TOTAL: 33 / PASSED: 0 / FAILED: 33 / SKIPPED: 0
  Reference: TOTAL: 33 / PASSED: 8 / FAILED: 21 / SKIPPED: 4

Changes from main branch:
  TOTAL: +0
  PASSED: -8
  FAILED: +12

New test failures (12):
  - basic
  - bignum
  - brief-vs-stat-zero-kernel-lies
  - bug-64316
  - cmp
  - diff3
  - help-version
  - large-subopt
  - strcoll-0-names
  - strip-trailing-cr
  - timezone
  - y2038-vs-32bit
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sylvestre
sylvestre reviewed Sep 29, 2026
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Comment thread src/side_diff.rs Outdated
// `process_half_line` left the cursor one column past the half width. The gutter marker
// belongs at the middle of the gutter (`separator_pos`), which is only `half_width + 1`
// when the gutter is 3 or 4 columns wide; pad up to it for wider gutters so the marker
// doesn't drift (see #269). `format_tabs_and_spaces` is a no-op when already at/past it.

@sylvestre sylvestre Sep 29, 2026

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4 lines of comment for a one-liner, could you please make it shorter? :)

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sylvestre
sylvestre reviewed Sep 29, 2026
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Comment thread src/side_diff.rs Outdated
// Regression test for #269: the `-y` gutter marker must sit at the middle of the gutter
// (separator_pos) regardless of gutter width. At the default width (gutter 3) the marker
// was already correct; at other widths it drifted. Here width=40 yields a wider gutter, so
// the marker must land at column 19 (matching GNU), not the old `half_width + 1`.

@sylvestre sylvestre Sep 29, 2026

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same here, please make it shorter

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sylvestre
sylvestre reviewed Sep 29, 2026
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Comment thread src/side_diff.rs
// (separator_pos) regardless of gutter width. At the default width (gutter 3) the marker
// was already correct; at other widths it drifted. Here width=40 yields a wider gutter, so
// the marker must land at column 19 (matching GNU), not the old `half_width + 1`.
#[test]

@sylvestre sylvestre Sep 29, 2026

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please also add a test in tests/integration.rs with -y --width=40

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@nagendramohan nagendramohan Sep 29, 2026

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Thanks! Shortened both comments and added an integration test covering -y --width=40 in both --expand-tabs and the default (tab-path) modes, asserting the marker sits at the gutter middle.

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sylvestre
sylvestre reviewed Sep 29, 2026
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Comment thread src/side_diff.rs
let params = Params {
tabsize: 8,
expand_tabs: true,
width: 40,

@sylvestre sylvestre Sep 29, 2026

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could you please also test with expand_tabs: false?
that is the default, and the padding goes through the tab path

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@nagendramohan
diff: address review — shorten comments and add -y width tests
ab9f8d9 
Shorten the two long comments per review, and add an integration test in
tests/integration.rs exercising `-y --width=40` in both the default
(expand_tabs: false, tab-padding path) and --expand-tabs modes, asserting
the gutter marker lands at the middle of the gutter.
@nagendramohan
nagendramohan requested a review from sylvestre September 29, 2026 05:51
sylvestre
sylvestre reviewed Sep 30, 2026
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Comment thread tests/integration.rs Outdated
}

// Visual (tab-aware) column of the `-y` gutter marker on the first output line.
fn side_marker_visual_column(output: &[u8], tabsize: usize) -> Option<usize> {

@sylvestre sylvestre Sep 30, 2026

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could we just compare the whole stdout instead of this helper?
simpler, and it would also check the exact tabs/spaces emitted

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@nagendramohan
diff: compare full -y stdout in the gutter marker test
add112b 
Per review, assert the exact stdout for both --expand-tabs and the
default tab path instead of a column helper, so the test also pins the
exact tabs/spaces emitted.
@sylvestre
sylvestre merged commit 7aa5409 into uutils:main Oct 5, 2026
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@sylvestre

sylvestre commented Oct 5, 2026

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Thanks for your PR
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@BrewTestBot BrewTestBot mentioned this pull request Oct 23, 2026
uutils-diffutils 0.6.0 Homebrew/homebrew-core#320660
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diff: -y draws the gutter marker at the wrong column unless the gutter is 3 or 4 columns wide

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@nagendramohan @sylvestre
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