test(formatter): add snapshot-based test infrastructure

[Dunqing]

Implement a flexible snapshot-based testing framework for oxc_formatter using insta and build-time test generation.

Features

• Auto-discovery: Tests are automatically discovered from tests/fixtures/ directory
• Individual test functions: Each fixture file gets its own test function for easy identification
• Hierarchical options: Support for options.json files at any directory level
• Multiple option sets: Test the same input with multiple formatting configurations
• Co-located snapshots: Snapshot files are stored next to test files (e.g., foo.js.snap)
• Comprehensive README: Detailed documentation for adding and running tests

Implementation

• build.rs: Scans tests/fixtures/ and generates test functions at build time
• tests/fixtures/mod.rs: Core test infrastructure with option resolution and snapshot generation
• tests/README.md: Complete guide for using the test framework
• Sample tests: Example tests demonstrating JS, JSX, TS, and nested configurations

🤖 Generated with Claude Code

Co-Authored-By: Claude [email protected]

[Dunqing]

• fix(formatter): print a line break incorrectly for directives #14577
• refactor(formatter): simplify foramtting import and export #14576
• refactor(formatter): remove SiblingNode #14551
• refactor(formatter): improve printing comments for special nodes #14544
• fix(formatter): correct printing comments that are around the StaticMemberExpression #14543
• fix(formatter): no need to wrap a parenthesis for TSConditionalType and TSFunctionType when its parent is TSUnionType and it only has one element #14540
• refactor(formatter): improve line break detaching logic in SourceText #14539
• fix(formatter): missing parenthesis for ComputedMemberExpression when its parent is an NewExpression #14530
• fix(formatter): missing parenthesis for PrivateInExpression when its parent is an UnaryExpression #14529
• fix(formatter): correct printing comments for logical expression #14500
• fix(formatter): should break even if the right side of the assignment is a require when it has a leading own line comment #14499
• fix(formatter): correct printing comments for the end of union type #14498
• fix(formatter): correct printing comments for try statement #14497
• fix(formatter): should expand the parent if the member chain will break #14487
• fix(formatter): correct printing comments around the expression of ComputedMemberExpression #14486
• fix(formatter): correct printing yield argument #14485
• fix(formatter): no need to wrap with parentheses for a type cast node #14484
• fix(formatter): ignore the leading line break for the first argument of the call expression #14483
• fix(formatter): correct checking comments between the operator and the right side for assignment like nodes #14482
• fix(formatter): block comments without a leading linebreak that are around the operator of the conditional expression should be printed as-is #14474
• fix(formatter): correct printing comments for for statements #14473
• fix(formatter): correct printing comments for assignment pattern #14469
• test(formatter): add snapshot-based test infrastructure #14400 👈 (View in Graphite)
• main

---

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

• 0-merge - adds this PR to the back of the merge queue
• hotfix - for urgent hot fixes, skip the queue and merge this PR next

You must have a Graphite account in order to use the merge queue. Sign up using this link.

An organization admin has enabled the Graphite Merge Queue in this repository.

Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codspeed-hq]

CodSpeed Performance Report

Merging #14400 will not alter performance

_{Comparing feat/formatter-snapshot-tests (bb43dc5) with main (9965676)¹}

Summary

✅ 33 untouched
⏩ 4 skipped²

Footnotes

1. No successful run was found on main (33b6cde) during the generation of this report, so 9965676 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 4 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. ↩

[Copilot]

Pull Request Overview

This PR implements a comprehensive snapshot-based testing framework for oxc_formatter using insta and build-time test generation. The framework enables automatic test discovery from fixture files and supports hierarchical configuration through options.json files.

Key changes include:

• Build-time test generation that scans tests/fixtures/ and creates individual test functions
• Core test infrastructure with option resolution and snapshot generation capabilities
• Comprehensive documentation explaining how to add and use the test framework

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/oxc_formatter/tests/mod.rs	Adds module declaration for fixtures test infrastructure
crates/oxc_formatter/tests/fixtures/mod.rs	Core test infrastructure implementing option parsing, formatting, and snapshot generation
crates/oxc_formatter/tests/README.md	Complete documentation guide for using the test framework
crates/oxc_formatter/build.rs	Build script that discovers test files and generates test functions at compile time
crates/oxc_formatter/Cargo.toml	Adds required dev dependencies for snapshot testing and JSON parsing

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[leaysgur]

Commented mainly about how to handle options. 👀

[graphite-app]

Merge activity

• Oct 12, 3:55 PM UTC: Dunqing added this pull request to the Graphite merge queue.
• Oct 12, 4:01 PM UTC: Merged by the Graphite merge queue.