Fix Shiki hang on inline struct type highlighting

[nighca]

Summary

• narrow the inline struct semicolon field rule in the xgo TextMate grammar
• avoid catastrophic regex behavior when Shiki tokenizes nested function types with inline struct parameters
• preserve normal highlighting for representative semicolon-separated struct fields

Testing

• verified the updated grammar file parses without errors
• reproduced the original pathological input in an isolated Shiki harness and confirmed codeToTokens and codeToHtml complete successfully after the grammar change
• verified a representative type T struct{X_0 int; X_1 float64} sample still produces highlighted HTML

Closes #2932

[gemini-code-assist]

Summary of Changes

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This pull request resolves a critical performance issue in the Shiki syntax highlighter, specifically targeting a regular expression within the Go+ TextMate grammar. The previous regex caused significant delays or hangs when processing complex inline struct type definitions, particularly those involving nested function parameters. The updated grammar rule prevents this catastrophic backtracking, ensuring efficient and correct highlighting for Go+ code without impacting standard struct field highlighting.

Highlights

• Grammar Refinement: Narrowed the inline struct semicolon field rule within the xgo TextMate grammar.
• Performance Fix: Addressed catastrophic regex behavior that occurred when Shiki tokenized nested function types containing inline struct parameters.
• Highlighting Preservation: Ensured normal highlighting is preserved for representative semicolon-separated struct fields.

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Changelog

• spx-gui/src/utils/xgo/gop-tm-language.json
  • Modified the regex pattern for inline struct field declarations to be more specific and prevent catastrophic backtracking.
  • Simplified the capture group structure for the inline struct field highlighting rule.

Activity

• Verified that the updated grammar file parses without errors.
• Reproduced the original pathological input in an isolated Shiki harness and confirmed successful completion of codeToTokens and codeToHtml after the grammar change.
• Verified that a representative type T struct{X_0 int; X_1 float64} sample still produces correctly highlighted HTML.

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[gemini-code-assist]

Code Review

This pull request effectively resolves a performance issue with the syntax highlighter by replacing a complex and inefficient regular expression. This simplification prevents catastrophic backtracking and is a significant improvement. I have identified a minor issue in the new regex concerning the matching of variable lists, which could result in incorrect highlighting for certain valid code formats. My suggestion aims to enhance the robustness of this matching.

[Copilot]

Pull request overview

This PR updates the xgo (GoPlus) TextMate grammar used by Shiki in spx-gui to avoid catastrophic regex behavior when highlighting inline struct{...} types containing semicolon-separated fields, addressing a browser hang during tokenization.

Changes:

• Replaced the inline-struct “semicolon field” matching rule with a simpler regex intended to avoid catastrophic backtracking.
• Kept capture-based highlighting for struct field names and types via existing #type-declarations patterns.

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[xgopilot]

Solid fix. The catastrophic backtracking (ReDoS) in the old regex was caused by nested quantifiers around [\\S]+ with an optional terminator — a textbook ambiguity that forced exponential backtracking on nested struct types. Replacing it with an unambiguous negated character class [^; `\"/}]+eliminates the ambiguity entirely. The simplification of the capture structure (flat vs. nested sub-patterns) is correct. Two minor notes left inline: the removed(?<=\{)lookbehind assumption and the stale"comment"` field.