FA-76393 / Email MIME structure / Member archive

Resolve a part's effective content type and charset: charset scope · case 03

Non-text parts report a charset taken from a meaningless parameter.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

header is the raw Content-Type value or None. The type is the lower-cased text before ";" with surrounding spaces removed; it is valid only with a non-empty major and minor separated by "/" and no inner space. Missing or invalid types default to message/rfc822 inside multipart/digest and text/plain everywhere else (parameters of an invalid header are ignored). text/* types get the charset parameter (quotes removed, lower-cased) or us-ascii; other types have charset None. Result [type, charset].

Why this case matters

Default and fallback types decide whether a part is rendered as text, as a nested message or as an attachment.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
charset on a binary type	`["image/png", "binary"]`	`["image/png", null]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.