The YAML grammar requires every directive to head an explicit document,
so a directive must be followed by a '---' marker. The scanner accepted a
directive with no document at all: '%YAML 1.2' alone, or '%YAML 1.2' then
a '...' document-end marker, parsed without error.
The scanner now records the line of a directive awaiting its document,
clears it at a document start, and rejects a still-pending directive at a
document-end marker and at stream end. Both scan drivers finalize through
the same stream-end path, so the check lives in one helper called from
each. The rule applies to any directive, including an unrecognized one
(which is otherwise still ignored); the directive test that relied on an
unrecognized directive parsing without a '---' is corrected to include
one, since that leniency is not permitted by the grammar.
Measured against the official YAML test-suite, parse-level conformance
rises from 253/333 (76.0%) to 255/333 (76.6%) with no regression.
Mihaela M
27c423dbb9