FA-76362 / Email MIME structure / Member archive

Assign IMAP-style section numbers to body parts: encapsulated multipart · case 02

Parts of an attached multipart message get an extra ".1" level, so fetching them returns the wrong entity.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

Returns [section, type] for every non-multipart entity in depth-first order. A single-part message body is section "1". Children of a multipart are numbered 1..n under the parent's number (nested multiparts get their own number). A message/rfc822 part is listed itself; if its encapsulated body is multipart, that body's children are numbered directly under the message part (P.1, P.2...); a single-part encapsulated body is P.1.

Why this case matters

Section numbers are how clients fetch individual parts; off-by-one numbering downloads the wrong attachment.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
attached multipart message	`[["1", "text/plain"], ["2", "message/rfc822"], ["2.1.1", "text/plain"], ["2.1.2", "image/jpeg"]]`	`[["1", "text/plain"], ["2", "message/rfc822"], ["2.1", "text/plain"], ["2.2", "image/jpeg"]]`	Failed

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