feat(linter/plugins): allow JS plugins to access globals

[lilnasy]

• This PR implements a naive, inefficient solution to Linter plugins: Pass globals to JS plugins #16359.
• To establish current and expected behavior, this PR serializes rust-resolved and -overridden globals once for every file.

Future work

• Add test for globals from the env field. Implement support if not currently supported.
• Optimization: we want to serialize globals for all files only once at the start of the lint run.

AI Usage

• This PR was drafted by Claude Sonnet 4.5 in Plan + Agent mode, then manually reviewed and iterated on.

[codspeed-hq]

CodSpeed Performance Report

Merging #16512 will not alter performance

_{Comparing lilnasy:globals-quick-dirty-and-inefficient (3a44ac0) with main (40b0134)¹}

Summary

✅ 4 untouched
⏩ 41 skipped²

Footnotes

1. No successful run was found on main (e24aabd) during the generation of this report, so 40b0134 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 41 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. ↩

[overlookmotel]

I know you've said this is just an experiment, but I think we should merge it!

Yes, it's inefficient to serialize globals for every file (ditto settings). But at least it works! Much better than just not supporting it at all, which is what we have now.

A few comments below - none major.

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We also support an env option in config: https://oxc.rs/docs/guide/usage/linter/config.html#configuration-file-format

I'm not sure globals from env already get merged into OxlintGlobals on Rust side, in which case it'll work already after this PR.

If so, we should add a test for that. If not, we should add support for env (simplest way would be to just apply env to OxlintGlobals on Rust side, before serializing to JSON). Either way, I suggest leaving that to a follow-up PR.

[lilnasy]

@overlookmotel Makes sense. I'll address the review comments tonight and add todo comments for performance.

[Copilot]

Pull request overview

This PR enables JavaScript plugins to access the globals configuration by passing serialized globals from Rust to JavaScript for each file during linting. The implementation follows the existing pattern used for settings, serializing the globals once per file to support folder-level overrides.

Key Changes:

• Added globals serialization in Rust and deserialization in TypeScript with lazy initialization
• Extended the ExternalLinterLintFileCb type signature to include globals JSON parameter
• Implemented globals conversion from "writeable" to "writable" for ESLint compatibility in JavaScript

Reviewed changes

Copilot reviewed 17 out of 18 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
crates/oxc_linter/src/lib.rs	Serializes globals to JSON and passes to external linter callback
crates/oxc_linter/src/external_linter.rs	Updates type signature to accept globals JSON parameter
crates/oxc_linter/src/context/host.rs	Adds getter method to expose globals from config
crates/oxc_linter/src/config/globals.rs	Adds TODO comment about adding serde rename for ESLint compatibility
apps/oxlint/src/run.rs	Updates type signature for globals parameter in JS callback
apps/oxlint/src/js_plugins/external_linter.rs	Passes globals JSON to JavaScript lint function
apps/oxlint/src-js/plugins/lint.ts	Accepts and processes globals JSON parameter, with incorrect import extension
apps/oxlint/src-js/plugins/globals.ts	New module implementing globals deserialization with "writeable" to "writable" conversion, contains incorrect import extension
apps/oxlint/src-js/plugins/context.ts	Exposes globals via languageOptions with lazy initialization
apps/oxlint/src-js/plugins/config.ts	Updates TODO to include globals setup
apps/oxlint/src-js/package/rule_tester.ts	Adds empty globals JSON parameter for testing
apps/oxlint/src-js/cli.ts	Forwards globals JSON parameter to lint function
apps/oxlint/src-js/bindings.d.ts	Updates type definition to include globals parameter
apps/oxlint/test/fixtures/globals/*	Test fixtures verifying globals functionality with base and override configurations

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[lilnasy]

Addressed all review comments. CI is failing because spell check flaked.