refactor: use Pattern enum instead of Cow<Pat> in javascript parser

[CPunisher]

Summary

This PR refactors the JavaScript parser to use a new Pattern enum instead of Cow<Pat> for representing AST patterns.

Key Changes:

• Introduced Pattern<'ast> enum in estree.rs to wrap various SWC AST pattern types.
• Replaced Cow<Pat> usage with Pattern<'ast> across JavascriptParser and its plugins.
• Removed deprecated warp_ident_to_pat helper.
• Updated walk_pattern, enter_pattern, and related methods to handle the new Pattern enum.

Rationale:

Using Pattern<'ast> allows us to work with references to the AST more directly, reducing the need for Cow and unnecessary cloning of Pat nodes, which should improve performance and simplify the code.

Related links

None.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

[netlify]

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[gemini-code-assist]

Summary of Changes

Hello @CPunisher, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly refactors the JavaScript parser by introducing a dedicated Pattern enum. This change aims to improve performance and simplify the codebase by allowing the parser to work with direct references to the Abstract Syntax Tree (AST) patterns, thereby reducing the need for Cow (Clone-on-Write) and avoiding unnecessary cloning of Pat nodes.

Highlights

• New Pattern Enum: Introduced a Pattern<'ast> enum in estree.rs to represent various SWC AST pattern types, providing a more direct way to work with AST references.
• Cow Replacement: Replaced all instances of Cow<Pat> with the new Pattern<'ast> enum across the JavascriptParser and its associated plugins, simplifying type handling.
• Deprecated Helper Removal: The warp_ident_to_pat helper function has been removed as it is no longer needed with the new Pattern enum, streamlining the codebase.
• Parser Method Updates: walk_pattern, enter_pattern, and other related methods within the JavascriptParser have been updated to correctly handle the new Pattern enum, ensuring compatibility and proper AST traversal.

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[Copilot]

Pull request overview

This PR refactors the JavaScript parser to replace Cow<Pat> with a new Pattern<'ast> enum for representing AST patterns. The refactoring aims to work with AST references more directly, reducing cloning and improving performance.

Key Changes:

• Introduced Pattern<'ast> enum with variants for Identifier, ObjectPattern, ArrayPattern, RestElement, AssignmentPattern, and Expression
• Removed Cow<Pat> usage and the deprecated warp_ident_to_pat helper function
• Updated pattern walking and entering methods to use the new Pattern type with proper lifetime annotations

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/rspack_plugin_javascript/src/visitors/dependency/parser/estree.rs	Defines new Pattern<'ast> enum and From<&'ast Pat> implementation
crates/rspack_plugin_javascript/src/visitors/dependency/parser/walk_pre.rs	Removes Cow import and updates to use Pattern::from
crates/rspack_plugin_javascript/src/visitors/dependency/parser/walk.rs	Removes warp_ident_to_pat, updates walk_pattern and related methods to use Pattern, replaces Cow::Borrowed/Cow::Owned with Pattern variants
crates/rspack_plugin_javascript/src/visitors/dependency/parser/mod.rs	Updates enter_pattern signature and removes Pat import
crates/rspack_plugin_javascript/src/parser_plugin/import_parser_plugin.rs	Updates to use Pattern instead of Cow<Pat> in scope parameters
crates/rspack_plugin_javascript/src/parser_plugin/amd/amd_require_dependencies_block_parser_plugin.rs	Removes Cow import and converts to Pattern
crates/rspack_plugin_javascript/src/parser_plugin/amd/amd_define_dependency_parser_plugin.rs	Updates to use Pattern and refactors get_ident_name to accept Pattern

---

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[gemini-code-assist]

Code Review

This pull request is a great refactoring that replaces Cow<Pat> with a new Pattern enum, which should improve performance and code clarity by reducing cloning. The changes are well-executed and consistent across the codebase. I've found one potential issue regarding the handling of invalid AST patterns that could lead to a panic, and I've provided suggestions to improve robustness.

[github-actions]

Rsdoctor Bundle Diff Analysis

Found 5 projects in monorepo, 0 projects with changes.

📊 Quick Summary

Project	Total Size	Change
react-10k	5.7 MB	0
react-1k	825.4 KB	0
react-5k	2.7 MB	0
ui-components	2.1 MB	0
rome	984.3 KB	0

Generated by Rsdoctor GitHub Action

[github-actions]

📦 Binary Size-limit

Comparing 817b70f to chore: limit workers for loader parallel tests (#12620) by CPunisher

❌ Size increased by 5.50KB from 47.87MB to 47.87MB (⬆️0.01%)

[codspeed-hq]

CodSpeed Performance Report

Merging #12625 will not alter performance

_{Comparing 01-05-refactor/pattern-ref (817b70f) with main (cd97e3b)}

Summary

✅ 16 untouched
⏩ 1 skipped¹

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩