validate resource name format before PopFirst in bundle parsing

[alhudz]

DecodeName and IsLocalDocumentKey accept a resource name from bundle input and call PopFirst(5) after only checking IsLocalResourceName, which still allows a four-segment name like projects/p/databases/d. That trips the length assertion inside PopFirst. ExtractLocalPathFromResourceName and DocumentKey::FromName already require size() > 4 and a documents segment, so this applies the same format check at the two bundle-reachable sites.

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[paulb777]

@alhudz Thanks for the PR. Please sign the CLA and we'll take a look

[alhudz]

@alhudz Thanks for the PR. Please sign the CLA and we'll take a look

Done

[paulb777]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds validation checks to ensure that Firestore resource paths have at least 5 segments and that the 5th segment (index 4) is "documents" before processing them, preventing potential out-of-bounds access. The review comments suggest minor readability improvements to make the size checks (< 5 and >= 5) more intuitive and directly aligned with the 5-segment requirement.

[gemini-code-assist]

Using path.size() < 5 is slightly more readable here as it directly aligns with the 5 segments required to safely call path.PopFirst(5) later in the function.

Suggested change

	if (!rpc_serializer_.IsLocalResourceName(path) || path.size() <= 4 ||
	path[4] != "documents") {
	if (!rpc_serializer_.IsLocalResourceName(path) || path.size() < 5 ||
	path[4] != "documents") {

[alhudz]

Switched to path.size() < 5, reads better against the PopFirst(5) below. Behaviour is the same.

[gemini-code-assist]

Using resource.size() >= 5 is slightly more intuitive than resource.size() > 4 as it directly corresponds to the 5 segments required for resource.PopFirst(5) and makes the relationship with index 4 (resource[4]) clearer.

Suggested change

	return IsLocalResourceName(resource) && resource.size() > 4 &&
	resource[4] == "documents" &&
	return IsLocalResourceName(resource) && resource.size() >= 5 &&
	resource[4] == "documents" &&

[alhudz]

Done, resource.size() >= 5 now.

[cherylEnkidu]

I will take a look for this next week.

[alhudz]

Folded in the two readability tweaks from the review (< 5 / >= 5 rather than <= 4 / > 4); the checks are behaviour-identical, just clearer against the PopFirst(5). The actual guard is the path[4] != "documents" segment check, which stops a 4-segment projects/p/databases/d name from reaching PopFirst(5) and tripping its length assert. Ready whenever you get to it.

[paulb777]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds path validation to ensure resource paths have at least 5 segments and that the 5th segment is "documents" before processing them, preventing potential out-of-bounds crashes. The reviewer notes that while this prevents a crash in PopFirst(5), DecodeName can still return paths that are not valid document keys, which could still trigger a crash in DecodeDocumentMetadata and DecodeDocument. The reviewer suggests adding validation using DocumentKey::IsDocumentKey in those functions.

[gemini-code-assist]

While this change successfully prevents a crash in PopFirst(5) for paths with fewer than 5 segments, DecodeName can still return a path that is not a valid document key (e.g., an odd number of segments or an empty path).

Because DecodeDocumentMetadata (line 643) and DecodeDocument (line 674) directly construct DocumentKey(path) using the result of DecodeName without checking DocumentKey::IsDocumentKey(path), any malformed bundle containing a non-document path (like a collection path or root documents path) will still trigger a HARD_ASSERT and crash the application.

Since DecodeName is also used for queries (where collection paths are valid), we should not enforce IsDocumentKey inside DecodeName itself. Instead, DecodeDocumentMetadata and DecodeDocument should be updated to validate the path using DocumentKey::IsDocumentKey(path) and call reader.Fail(...) if it is invalid, before attempting to construct the DocumentKey.