fix(linter): permit $schema .oxlintrc.json struct

[Copilot]

Fix: Allow $schema in .oxlintrc.json while maintaining deny_unknown_fields

Problem

• The Oxlintrc struct has #[serde(deny_unknown_fields)] which rejects all unknown fields
• Users commonly use $schema in their .oxlintrc.json files for IDE support (as shown in documentation examples)
• This causes deserialization to fail

Solution

Added a schema field to the Oxlintrc struct that:

• Is properly named $schema via #[serde(rename = "$schema")]
• Is optional (Option<String>) and skips serialization when None
• Maintains deny_unknown_fields for other unknown properties
• Follows the same merge behavior as other optional fields (self takes priority)

Changes

1. Added schema field to Oxlintrc struct with appropriate serde attributes
2. Removed manual $schema injection from generate_schema_json() - now auto-generated
3. Updated merge() function to handle the new field correctly
4. Added comprehensive tests for deserialization, serialization, and merge behavior
5. Updated schema JSON - $schema now appears first and has correct type ["string", "null"]
6. Fixed CI failures:
   • Resolved clippy warning about unnecessary raw string hashes
   • Updated website_linter snapshot to include $schema field

Testing

✅ Config files with $schema are now accepted
✅ Config files without $schema still work
✅ Unknown fields are still properly rejected
✅ Merge behavior gives priority to self over other
✅ All existing tests pass (878 tests)
✅ Schema generation produces correct output
✅ Clippy checks pass
✅ Website linter tests pass

Original prompt

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This section details on the original issue you should resolve

<issue_title>linter: $schema in .oxlintrc.json causes failure to deserailize</issue_title>
<issue_description>cc @connorshea

https://github.com/oxc-project/oxc-ecosystem-ci/actions/runs/20336440475/job/58424680576</issue_description>

<agent_instructions>This broke in d446c43, we should keep deny unknonw fields, but allow $schema</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes linter: $schema property in .oxlintrc.json causes serde failure to deserailize #17059

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[camc314]

@copilot fix lint and test CI jobs

[codspeed-hq]

CodSpeed Performance Report

Merging #17060 will not alter performance

_{Comparing copilot/fix-linter-schema-issue (bbea0fe) with main (fd03131)}

Summary

✅ 4 untouched
⏩ 41 skipped¹

Footnotes

1. 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. ↩

[Copilot]

Pull request overview

This PR fixes a deserialization failure when $schema is present in .oxlintrc.json configuration files by adding explicit support for the field while maintaining strict validation of other unknown fields.

Key Changes:

• Added schema field to Oxlintrc struct with proper serde configuration
• Updated merge logic to handle the new optional field
• Removed manual schema injection in favor of auto-generation

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/oxc_linter/src/config/oxlintrc.rs	Added schema field to Oxlintrc struct with appropriate serde attributes, updated merge logic, and added comprehensive tests
npm/oxlint/configuration_schema.json	Updated schema with auto-generated $schema property definition (now positioned first with correct type)
crates/oxc_linter/src/snapshots/schema_json.snap	Updated snapshot to reflect schema changes

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[camc314]

@copilot CI is failing. fix it

[camc314]

@copilot fix the failing CI

[Copilot]

@copilot fix the failing CI

Fixed in 679492d. Resolved:

• Clippy warning: removed unnecessary hashes from raw string literal
• Website linter snapshot: updated to include $schema field documentation