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The spec forbids U+0000–1F and U+007F in unbracketed destinations. The handwritten scanner only stopped on whitespace, so [a](\x01) became a link. Fixes commonmark#127
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Summary
The handwritten unbracketed destination scanner stops on
c <= 0x20 || c === 0x7F(the old whitespace set plus the remaining controls and DEL). It only stopped on whitespace (space/ tab / LF / VT / FF / CR), so[a](\x01)became<a href="%01">.Robin Stocker reported this against spec 0.28; the copy of spec 0.31.2 in this repo still states that unbracketed destinations must not contain ASCII control characters (
U+0000–1ForU+007F) or space. Inline links, images, and reference definitions all go through this scanner.Angle-bracket destinations (
<...>) are a different production and still allow controls other than NUL/line endings. NUL is still replaced with U+FFFD before parsing, so[a](\x00)remains a link to the replacement character.Stop (do not
return null) on space/control in the unbracketed form only. Alternative: fail the destination immediately, and/or also reject controls inside<...>.Space in this loop already stops rather than failing. That matches the reporter's "doesn't stop" and markdown-it's destination helper. Can switch to failing closed on the first control, or to rejecting controls inside
<...>.Fixes #127
Test plan
npm test(748 passed, including the five new Link destination parsing accepts control characters (but should not) #127 cases)%01output comes back) and pass with it restoredlib/inlines.jsandtest/test.jsmake benchbefore/after (not run here; the new check replaces a per-character regex)