refactor(tasks): improve terminal diff output with context lines

[Dunqing]

Summary

Improves the print_diff_in_terminal function with better readability and a simpler API:

API Changes:

• print_diff_in_terminal(expected, result) - Simple API that takes two strings
• print_text_diff(diff) - For when you already have a TextDiff (e.g., to use diff.ratio())

Features:

• Show 3 lines of context above and below each change
• Add line numbers with gutter separator (│)
• Add blank line between adjacent hunks for visual separation
• Add ... separator when lines are skipped between hunks
• Use single-pass streaming algorithm with small fixed-size buffer
• Colors: red (-) for deletions, green (+) for insertions, dim for context

Formatter Example:

• Added --diff flag to show diff between original and formatted code

Example output:

    1 │class A {
    2 │  #x;
    3 │}
-   4 │var _x = /* @__PURE__ */ new WeakMap();
-   5 │var _B_brand = /* @__PURE__ */ new WeakSet();
    4 │class B {

-   7 │  constructor() {
-   8 │    babelHelpers.classPrivateMethodInitSpec(this, _B_brand);
-   9 │    babelHelpers.classPrivateFieldInitSpec(this, _x, void 0);
+   5 │  #x;
+   6 │  #y() {
+   7 │    this.#x;
    8 │  }

-  11 │}
-  12 │function _y() {
-  13 │  babelHelpers.classPrivateFieldGet2(_x, this);
    9 │}

Test plan

• cargo check -p oxc_tasks_common passes
• Clippy passes
• Verified output with just test-transform --filter "plugins-integration/class-features-node-12/input.js"

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR refactors the print_diff_in_terminal function to improve the readability of diff output by adding context lines (like git diff), line numbers with a gutter separator, and gap separators between change hunks. The implementation uses a streaming algorithm with a fixed-size buffer to avoid collecting all lines in memory.

Changes:

• Added context line support showing 3 lines before and after each change
• Added line numbers with │ gutter separator and improved formatting
• Implemented streaming algorithm using VecDeque buffer for efficient memory usage
• Added comprehensive documentation with example output

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[Dunqing]

I really like using AI to improve the debugging experience.

[codspeed-hq]

Merging this PR will not alter performance

✅ 42 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing refactor/improve-diff-terminal-output (92562bd) with main (85ab400)²}

Footnotes

1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (b8a371d) during the generation of this report, so 85ab400 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Dunqing]

• fix(formatter): preserve trailing comments before the semicolon in class methods without a body #18446
• chore(formatter): support --diff in example #18443
• chore(tasks): unify printing differences for mismatch code #18441
• chore(prettier_conformance): improve the information that is shown in filter #18439
• refactor(tasks): improve terminal diff output with context lines #18437 👈 (View in Graphite)
• main

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[leaysgur]

I've just remembered I tried to apply https://github.com/mitsuhiko/similar/blob/main/examples/terminal-inline.rs once and forget…🫢

[graphite-app]

Merge activity

• Jan 23, 8:47 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Jan 23, 8:59 AM UTC: Merged by the Graphite merge queue.

[Dunqing]

I've just remembered I tried to apply https://github.com/mitsuhiko/similar/blob/main/examples/terminal-inline.rs once and forget…🫢

TIL, it looks good too!