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Fix: Add memoization to containsRecursiveSingularField to prevent exponential traversal #2014

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Fix: Add memoization to containsRecursiveSingularField to prevent exponential traversal #2014

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10 changes: 10 additions & 0 deletions Sources/protoc-gen-swift/MessageStorageDecision.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,16 @@ private func analyze(descriptor: Descriptor) -> AnalyzeResult {
// in the cycle must be defined in the same file.
guard messageType.file === initialFile else { return false }

// If this message has already been fully analyzed, skip re-traversal.
// Without this check, well-connected graphs (like large combined.proto files
// with hub types referenced by hundreds of messages) cause exponential
// re-traversal because recursionHelper does not consult the cache.
// Any cycle involving this message would already have been detected and
// written into analysisCache when it was first analyzed.
if analysisCache.wrappedValue[messageType.fullName] != nil {
return false
}

// Did things recurse?
if let first = messageStack.firstIndex(where: { $0 === messageType }) {
// Mark all those in the loop as using storage.
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