Parameter value "" (quoted-string, empty string value)

[bathos]

I believe the current parsing algorithm is intended to describe a superset of the RFC grammar, but in one respect it appears to depart:

§ 4.4 Parsing a MIME type

In step 7’s substeps, when the value portion of a parameter is a quoted string, the parameterValue being assembled is the string value (that is, with escapes resolved and without the surrounding quotation marks).

In step 8, the resulting key-value pair is only appended if “parameterValue is not the empty string.”

Contrast with the grammar in the RFCs, where key="" is permitted (the quoted portion is the production quoted-string, RFC 7230 § 3.2.6*). For this input, parameterValue will have been the empty string, so the pair will be ignored.

Is this an intentional departure, am I missing another step here, or is it a mistake?

If it is a mistake, note that the empty string check is still required, but only in the not-a-quoted-string branch (11 -> 7 -> 2).

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* DQUOTE *( qdtext / quoted-pair ) DQUOTE, note the kleene star

[annevk]

Thanks for spotting that, that is unintentional!

[annevk]

cc @hsivonen @MattMenke2