FA-76474 / Email MIME structure / Member archive

Resolve cid: references inside multipart/related: scheme case · case 04

References written as "CID:" are not recognised as content-id URLs.

Member previewVariant 4 · 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
scheme casing	`{"resolved": [["CID:pic@x", null], ["Cid:pic@x", null], ["http://pic@x", null]], "root": 0, "unused": [1]}`	`{"resolved": [["CID:pic@x", 1], ["Cid:pic@x", 1], ["http://pic@x", null]], "root": 0, "unused": []}`	Failed

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