feat(oxfmt): Support formatting JSON files

[leaysgur]

• Added support for JSON like files
  • Does not use linguist-data; instead, directly adopts the results extended by Prettier
  • Since tsconfig.json is typically jsonc, added our own support for it
• Existing tests were modified as JSON became a format target

[leaysgur]

• feat(oxfmt): Support config for prettier formatFile() #16526
• feat(oxfmt): Support formatting HTML, YAML, GraphQL, Handlerbars, Markdown, CSS files #16524
• feat(oxfmt): Support formatting JSON files #16523 👈 (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.

[Copilot]

Pull request overview

This PR adds support for formatting JSON files in oxfmt by integrating an external formatter (Prettier) via NAPI. The implementation distinguishes between different JSON variants (strict JSON, JSONC with comments, and json-stringify for package.json) and delegates formatting to the appropriate Prettier parser.

Key changes:

• Implemented external formatter support for JSON/JSONC files using Prettier parsers
• Added PHF-based file pattern matching for efficient JSON file type detection
• Updated test fixtures to exclude JSON/JSONC files from internal formatter tests

Reviewed changes

Copilot reviewed 13 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
apps/oxfmt/src/core/support.rs	Added get_external_parser_name function with comprehensive file type detection logic using PHF sets for JSON, JSONC, and JSON5 files; includes unit tests
apps/oxfmt/Cargo.toml	Added phf dependency with macros feature for efficient static set lookups
Cargo.lock	Updated lockfile to include phf dependency
apps/oxfmt/test/external_formatter.test.ts	New test suite verifying JSON formatting through external formatter for basic JSON, package.json, and tsconfig files
apps/oxfmt/test/fixtures/external_formatter/*.json	Test fixtures demonstrating unformatted JSON files with various formatting issues
apps/oxfmt/test/__snapshots__/external_formatter.test.ts.snap	Snapshot showing before/after formatting results for JSON files
apps/oxfmt/test/config_file.test.ts	Updated to exclude JSON/JSONC files from config file discovery tests using !*.{json,jsonc} pattern
apps/oxfmt/test/__snapshots__/config_file.test.ts.snap	Updated snapshots reflecting exclusion of JSON/JSONC files
apps/oxfmt/test/fixtures/config_file/*.jsonc	Added trailing commas to JSONC config files (valid JSONC syntax)
apps/oxfmt/test/__snapshots__/config_ignore_patterns.test.ts.snap	Updated to show JSON/JSONC files being formatted instead of causing "no files matched" errors
apps/oxfmt/test/fixtures/config_ignore_patterns/fmtrc.jsonc	Reformatted with proper indentation

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codspeed-hq]

CodSpeed Performance Report

Merging #16523 will not alter performance

_{Comparing 12-05-feat_oxfmt_support_formatting_json_files (264bf78) with main (a607cc4)}

Summary

✅ 42 untouched
⏩ 3 skipped¹

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. ↩

[leaysgur]

It's expected, unavoidable, but it impacts performance.

Here's what the results looked like when I ran it locally against the outline repository.
This repository contained about 46 .json files.

❯ node node_modules/oxfmt-dev/cli.js --check repos/outline/'

Checking formatting...

repos/outline/app/actions/definitions/apiKeys.tsx (0ms)
...
repos/outline/shared/utils/urls.ts (0ms)
repos/outline/tsconfig.json (48ms)

Format issues found in above 1053 files. Run without `--check` to fix.
Finished in 381ms on 1966 files using 8 threads.

🆚

❯ node node_modules/oxfmt-dev/cli.js --check repos/outline/ '!*.json'

Checking formatting...

repos/outline/app/actions/definitions/apiKeys.tsx (0ms)
...
repos/outline/shared/utils/urls.ts (0ms)

Format issues found in above 1052 files. Run without `--check` to fix.
Finished in 68ms on 1915 files using 8 threads.

And time | ... results:

./node_modules/.bin/prettier repos/outline/**/*.json -w  0.69s user 0.08s system 157% cpu 0.487 total

node node_modules/oxfmt-dev/cli.js repos/outline/**/*.json  0.67s user 0.06s system 174% cpu 0.422 total

But yes, it's working!

NOTE: Currently, formatted string on the JS side are sent back to the Rust side, then saved to disk.

I tried writing them directly to disk from the JS side too, but this did not yield significant improvement.

Especially for JSON, I think it possible to support by tweaking usage of oxc_formatter a bit, though.

[graphite-app]

Merge activity

• Dec 5, 7:55 AM UTC: Dunqing added this pull request to the Graphite merge queue.
• Dec 5, 8:02 AM UTC: Merged by the Graphite merge queue.