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Resolve cid: references inside multipart/related: unused excludes root · case 02

The root document is reported as an unreferenced related part.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

related has params (optional start, with angle brackets) and parts with optional cid values such as " <img@x> ". Content ids are compared after trimming spaces and angle brackets. The root is the part whose id equals the start id, else the first part. Each reference is a URL; the "cid:" scheme is case-insensitive and the rest is percent-decoded. A reference resolves to the first non-root part with an equal id, else None. Result {root, resolved [[ref, index]...], unused: non-root indexes nobody referenced}.

Why this case matters

Inline images and style sheets in HTML mail are located through Content-ID references.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
padded content id	`{"resolved": [["cid:pic2@x", 1]], "root": 0, "unused": [0]}`	`{"resolved": [["cid:pic2@x", 1]], "root": 0, "unused": []}`	Failed

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