FA-76533 / Email MIME structure / Member archive

Build a bounded MIME tree summary from parser events: depth limit · case 03

One more nesting level than configured is accepted.

Member previewVariant 3 · 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
three levels with limit two	`{"depth": 3, "errors": [], "leaves": 4}`	`{"depth": 2, "errors": ["too-deep"], "leaves": 3}`	Failed

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