This might break Rust analysis for users who have pinned v3 (or similar) of the Action as well as a CodeQL CLI >= 2.19.3 && < 2.22.1 and who used CODEQL_ENABLE_EXPERIMENTAL_FEATURES. I agree that it's not unreasonable to ask users to upgrade to a newer CLI version in that case, but perhaps we should give them some warning first before breaking their workflows over night when the next Action release happens? That said, it's not clear to me that a warning in the output would necessarily be noticed. I don't know if we have any data to know how many people would be affected.

in that situation (version 2.19.3..2.22.1 and CODEQL_ENABLE_EXPERIMENTAL_FEATURES=true) codeql resolve languages does give rust, which means that (await codeql.resolveLanguages()).rust is not undefined. The only change then is that users lose the Experimental Rust analysis enabled log line, but no functional change happens.

uh, actually, now I see that that log line was dead code anyway!