refactor(linter/plugins): store source text in end of buffer

[overlookmotel]

Previously we had to store source text at start of buffers sent to JS via raw transfer.

#18376 made changes to how raw transfer deserializer handles strings, in order to support files containing a BOM. Building on that, we're now able to remove the requirement that source text be at start of the buffer entirely.

This PR changes the deserializer used in Oxlint JS plugins to accept source text being anywhere in the buffer, as long as no other strings are after it. In practice this just means that the source text must be allocated before anything else, which is easy to satisfy.

Now the source text can be allocated with just the usual safe allocator.alloc_str(source_text) method.

This change removes a ton of dodgy workarounds and unsafe code we used previously to get source text at the start of buffer. It makes the code less labyrinthine and far less likely a slip up can inadvertently introduce UB.

Note: In napi/parser, source text still is at start of the buffer, as that's simpler and more efficient when the source text is written into the buffer on JS side. This change only affects Oxlint.

[overlookmotel]

• feat(oxc_allocator)!: remove dangerous Allocator methods #18715
• refactor(linter/plugins): store source text in end of buffer #18714 👈 (View in Graphite)
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing om/01-29-refactor_linter_plugins_store_source_text_in_end_of_buffer (2c6c42b) with main (051cfcf)¹}

Summary

✅ 46 untouched benchmarks
⏩ 3 skipped benchmarks²

Footnotes

1. No successful run was found on main (b82faec) during the generation of this report, so 051cfcf was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 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. ↩

[Copilot]

Pull request overview

This PR refactors how source text is stored in buffers for Oxlint JS plugins, moving it from the start to the end of the buffer. This change simplifies the code significantly by removing unsafe workarounds and making the implementation more maintainable.

Changes:

• Refactored string deserializer to detect source text by checking if position is >= sourceStartPos (for linter) instead of < sourceEndPos
• Updated parse function to accept source_start parameter and position source text at end of buffer
• Removed RawTransferFileSystem and its complex unsafe file reading implementation, now using standard OsFileSystem
• Simplified source text allocation from unsafe alloc_bytes_start to safe alloc_str
• Added ACTIVE_SIZE and CHUNK_FOOTER_SIZE constants for better buffer size calculations
• Removed complex allocator reset logic that was restoring data pointer to start

Reviewed changes

Copilot reviewed 11 out of 19 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tasks/ast_tools/src/generators/raw_transfer.rs	Updated string deserializer to check pos >= sourceStartPos for linter; added CHUNK_FOOTER_SIZE constant and ACTIVE_SIZE calculation
napi/parser/src/generated/raw_transfer_constants.rs	Added CHUNK_FOOTER_SIZE constant
napi/parser/src-js/generated/constants.js	Added ACTIVE_SIZE constant for buffer size calculations
crates/oxc_linter/src/lint_runner.rs	Removed file_system parameter, now always uses OsFileSystem
crates/oxc_linter/src/lib.rs	Simplified source text allocation to use alloc_str instead of unsafe alloc_bytes_start
crates/oxc_allocator/src/pool/fixed_size.rs	Removed complex data pointer restoration logic from reset method
crates/oxc_allocator/src/generated/fixed_size_constants.rs	Added CHUNK_FOOTER_SIZE constant
crates/oxc_allocator/src/from_raw_parts.rs	Added compile-time check to verify CHUNK_FOOTER_SIZE matches expected value
apps/oxlint/src/lint.rs	Removed file_system parameter from lint_files call and removed associated configuration logic
apps/oxlint/src/js_plugins/raw_fs.rs	Deleted entire file - no longer needed with new approach
apps/oxlint/src/js_plugins/parse.rs	Updated to accept source_start parameter, position source text at end, and set allocator cursor accordingly
apps/oxlint/src/js_plugins/mod.rs	Removed RawTransferFileSystem export
apps/oxlint/src/generated/raw_transfer_constants.rs	Added CHUNK_FOOTER_SIZE constant
apps/oxlint/src-js/package/parse.ts	Calculate sourceStartPos as ACTIVE_SIZE - maxSourceByteLen and pass to parseRawSync
apps/oxlint/src-js/generated/deserialize.js	Removed sourceEndPos variable; updated string detection to use pos >= sourceStartPos
apps/oxlint/src-js/generated/constants.ts	Added ACTIVE_SIZE constant
apps/oxlint/src-js/bindings.d.ts	Updated parseRawSync signature to include sourceStart parameter
apps/oxlint/Cargo.toml	Removed unused simdutf8 dependency
Cargo.lock	Updated to reflect removed simdutf8 dependency

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[overlookmotel]

I wrote this shameful hacky code originally, so I think I know it better than anyone. So merging without review.

[graphite-app]

Merge activity

• Jan 30, 12:51 AM UTC: overlookmotel added this pull request to the Graphite merge queue.
• Jan 30, 12:58 AM UTC: Merged by the Graphite merge queue.