dev meeting 2025 09 17

Meeting notes

Attendees: @ElectreAAS, @Leonidas-from-XIV, @art-w, @rgrinberg, @Alizter, @aguluman

Parametric libraries (@art-w)

• Good progress!
• There will be more PRs going forward
• Modules have to be instantiated in dependency order
  • For local modules that is already computed by dune
  • For OPAM dependencies ocamlobjinfo can be used, but make sure it is not called multiple times
• Executables that need to instantiate libraries might cause duplication
  • Store instantiation in a shared location, this is what js_of_ocaml is doing in some places
  • Preferrably path-addressable, but otherwise a similar hashing strategy can be used as PPXes do
• Need to fix Merlin and Odoc
  • Jane Street has some basic fixes that makes Odoc not crash
  • dot-merlin can be patched

Copy lock dir rules (@Leonidas-from-XIV)

• How to copy from the build directory to the build directory?
  • Any way is fine as long as dependencies are tracked
• Race condition for writing to source and reading the source to determine whether generate the rules
  • The dev-tools are doing this in a broken way, locking and running is not supported in that way
  • It's ok to exclude them for now, it's an experimental feature anyway
  • Dev tool lock files should live in _build anyway, the fact they're in the source is a hack
• Location reporting
  • Need to map back to the original source if it was copied from the source
  • There is no general mechanism to do this mapping, it's on to just postprocess

Portable lock file slowdown (@rgrinberg)

• Slows down parsing a lot because it checks for portable lock dirs a lot
• It is on the Tarides MVP target list but it would be good to get it fixed soon
• Will help copy rules as well
• Maybe @ElectreAAS can fix it, the fix should be fairly simple
• Otherwise @gridbugs should be back by the end of the month
• #12244 and #12248