YAML lexer treats // as a comment, breaking values that start with //

[walles]

Describe the bug

Since v2.25.0 the YAML lexer has an unconditional //.*$ → Comment rule, added in #1278 to address #1271.

YAML has exactly one comment syntax: #. Per YAML 1.2.2 §6.6 Comments, "An explicit comment is marked by a # indicator." As a result, any value that begins with // is now highlighted as a comment. This breaks UNC paths and protocol-relative URLs.

Values with // in the middle are unaffected — url: https://example.com/x and regex: "a//b" still highlight correctly. It is specifically values starting with //.

I left a comment on #1271 explaining why that issue's premise was incorrect: its sample is not valid YAML, so the rule improves rendering of invalid YAML at the cost of misrendering valid YAML.

To Reproduce

Paste into the Chroma Playground with language YAML:

path: //server/share
proto: //cdn.example.com/lib.js
url: https://example.com/x
regex: "a//b"
comment: # real YAML comment

Expected: only the last line contains a comment.
Actual: lines 1 and 2 have their values highlighted as comments.

🤖 Report written by Claude (Sonnet 5)