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Build a bounded MIME tree summary from parser events: nested skip depth · case 02

After skipping an over-deep subtree with nested containers, parsing resumes inside it and misattributes its parts.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

events are ["open", type] (multipart start), ["leaf", type, size] and ["close"]. The root multipart has depth 1. An open that would exceed max_depth records "too-deep" and its whole subtree (including nested opens) is skipped, but it still counts as a child of its parent. A multipart closing with no children records "empty-multipart", a close with nothing open records "stray-close", and containers left open record "unclosed". Result {leaves, depth (maximum reached), errors}.

Why this case matters

Bounding MIME nesting protects mail parsers from resource exhaustion while keeping the reachable structure intact.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
deep skipped subtree	`{"depth": 1, "errors": ["too-deep", "stray-close", "stray-close"], "leaves": 2}`	`{"depth": 1, "errors": ["too-deep"], "leaves": 1}`	Failed

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