fix(linter/plugins): prevent comments being accessed after file is linted

[overlookmotel]

Follow on after #14637. I now realize that there was a subtle race condition.

We use astId counter in the getter for program.comments, to check that the getter is not called after that AST is done with. Buffers are reused, so the buffer held in local reference is the same, but the contents of the buffer could have changed - it may now contain a different AST.

Previously, astId was incremented in deserializeProgram. So if comments getter is accessed after another AST is deserialized, it (rightly) throws.

But there's a small period of time in between walking the AST on JS side and the next call to deserializeProgram. During that period, the buffer may be being mutated on Rust side (in another thread), but astId hasn't been incremented yet, so the localAstId === astId check in comments getter will pass, and it won't throw an error as it should.

Fix this by incrementing astId as soon as traversal of this AST ends, instead of before deserializing the next AST begins.

[overlookmotel]

• fix(linter/plugins): prevent comments being accessed after file is linted #14727 👈 (View in Graphite)
• refactor(linter/plugins): rename function #14726
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging #14727 will not alter performance

_{Comparing 10-17-fix_linter_plugins_prevent_comments_being_accessed_after_file_is_linted (5d6165e) with main (3029dfb)¹}

Summary

✅ 37 untouched

Footnotes

1. No successful run was found on 10-17-refactor_linter_plugins_rename_function (4568276) during the generation of this report, so main (3029dfb) was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[overlookmotel]

Merge activity

• Oct 17, 1:18 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Oct 17, 1:19 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
• Oct 17, 1:30 PM UTC: Merged by the Graphite merge queue.

[overlookmotel]

cc @lilnasy FYI. I didn't spot this before. Highly unlikely this would be a problem in practice, but I think worth covering all bases...