Remove most backtracking from lockdir parser #12487
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rgrinberg
approved these changes
Sep 23, 2025
Indeed. In the issue, I wrote down my investigation of the remaining slowness. |
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Thanks for the thorough investigation. Do you want to send PR's for those fixes? Seems a bit silly if I am just going to redo the work from your notes. |
To parse both portable and non-portable lockdirs with mostly the same code, the parser would attempt to parse fields with the non-portable lockdir syntax and fall back to the portable syntax should parsing fail. This led to the generation of parse errors when the first attempt at parsing a field would fail, and even though these errors are discarded, generating them took a noticeable amount of time. This changes the parsing logic to only attempt to parse fields in a single syntax, determined by the presence of the `solved_for_platforms` field in the lockdir metadata file. This field is present precisely when a lockdir is portable. Signed-off-by: Stephen Sherratt <[email protected]>
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I sent the changes I have, but I don't have a broad understanding of the code, so while the changes are enough to prove that dune should be much faster, maybe some other change would be even better. |
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To parse both portable and non-portable lockdirs with mostly the same code, the parser would attempt to parse fields with the non-portable lockdir syntax and fall back to the portable syntax should parsing fail. This led to the generation of parse errors when the first attempt at parsing a field would fail, and even though these errors are discarded, generating them took a noticeable amount of time.
This changes the parsing logic to only attempt to parse fields in a single syntax, determined by the presence of the
solved_for_platformsfield in the lockdir metadata file. This field is present precisely when a lockdir is portable.Fixes #12248