perf: replace O(n) indexOf+children with O(1) nextSibling traversal in C# analyzer

[github-actions]

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Summary

Eliminates two O(n) linear scans over parent.children in CSharpMetricsAnalyzer by replacing them with direct nextSibling pointer walks (O(1) per step in tree-sitter's underlying C structure).

Changes

src/metricsAnalyzer/languages/csharpAnalyzer.ts

1. getMethodBody — preprocessor sibling search

Previously:

const methodIndex = parent.children.indexOf(node);  // O(n) scan
for (let i = methodIndex + 1; i < parent.children.length; i++) {
  const sibling = parent.children[i];
  ...
}

Now:

let sibling = node.nextSibling;  // O(1) pointer walk
while (sibling) {
  ...
  sibling = sibling.nextSibling;
}

2. hasMatchingColonInSiblings — ternary colon detection

Previously:

const errorIndex = parent.children.indexOf(errorNode);  // O(n) scan
for (let i = errorIndex + 1; i < Math.min(errorIndex + 3, ...); i++) {
  const sibling = parent.children[i];
  ...
}

Now:

let sibling = errorNode.nextSibling;  // O(1) pointer walk
for (let steps = 0; sibling && steps < 2; steps++, sibling = sibling.nextSibling) {
  ...
}

Also simplifies the parent-null guard in hasMatchingColonInSiblings (no longer needs parent at all since nextSibling handles missing siblings gracefully).

Rationale

Array.prototype.indexOf walks the entire children array to find the node. In large C# classes with many members, this linear scan runs every time a preprocessor-split method or ternary in an ERROR node is encountered. The SyntaxNode.nextSibling property in tree-sitter is a constant-time pointer dereference, making both paths run in O(k) where k is bounded by either the class size found (early exit on preproc_if or another method) or 2 (the fixed step limit for colon detection).

Test Status

npm run compile  ✅  (0 errors)
npm run lint     ✅  (0 warnings)
npm run test:unit  ✅  201 passing, 0 failing

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[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.46%. Comparing base (fd7d1f7) to head (badb8e2).

Files with missing lines	Patch %	Lines
src/metricsAnalyzer/languages/csharpAnalyzer.ts	75.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #499      +/-   ##
==========================================
+ Coverage   81.37%   81.46%   +0.08%     
==========================================
  Files          13       13              
  Lines        4366     4354      -12     
  Branches      442      441       -1     
==========================================
- Hits         3553     3547       -6     
+ Misses        812      806       -6     
  Partials        1        1              

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[Copilot]

🟡 Not ready to approve

The new sibling-walk stop condition still only breaks on class/interface declarations and should also stop on other type declarations (struct/record/enum) to avoid mis-associating a later preproc_if as the method body.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

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Pull request overview

Optimizes the C# cognitive complexity analyzer’s tree-sitter AST traversal by replacing parent.children.indexOf(...) + indexed loops with nextSibling pointer walks, reducing repeated linear scans when handling preprocessor-split method bodies and fragmented ternary operators.

Changes:

• Updated getFunctionBody to search for preproc_if using node.nextSibling traversal instead of scanning parent.children.
• Updated hasMatchingColonInSiblings to check up to two nextSiblings instead of scanning via indexOf + bounds math.

File summaries

File	Description
src/metricsAnalyzer/languages/csharpAnalyzer.ts	Replaces sibling lookup loops that depend on parent.children.indexOf with nextSibling traversal for better performance in C# AST analysis.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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