test: verify incremental builds with alias re-exported libraries (#4572)#14129
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rgrinberg merged 1 commit intoocaml:mainfrom Apr 10, 2026
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…ml#4572) Add test verifying that when a library re-exports a dependency via a module alias (module Impl = Impl), incremental builds correctly recompile consumers when the re-exported library's .cmi changes. Soft changes (implementation only, no .cmi change) can safely skip recompilation due to -opaque. Hard changes (.cmi modified) must trigger recompilation to avoid inconsistent interface assumptions. Reproduction case from @art-w. Signed-off-by: Robin Bate Boerop <me@robinbb.com>
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| Main is rebuilt (necessary — impl.cmi changed and main.ml uses | ||
| Impl through the Alias re-export): | ||
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| $ dune trace cat | jq -s 'include "dune"; [.[] | targetsMatchingFilter(test("Main"))] | length | . > 0' |
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Do we need the length and predicate here? Seeing the target would be enough.
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Alas, yes, as the length is actually different on different platforms (Mac vs. non-Mac), which caused what I had here originally (the unfiltered uncounted output) to fail CI.
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... because the output was different on different platforms, and even the filtered output was different (hence the non-zero count check instead of a firm count).
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@rgrinberg Back to you. I can't give you what you want (per my comment). I wanted it, too. :-( |
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Summary
Add test verifying that when a library re-exports a dependency via a
module alias (
module Impl = Impl), incremental builds correctlyrecompile consumers when the re-exported library's
.cmichanges..cmichange) can safely skiprecompilation due to
-opaque.cmimodified) must trigger recompilation to avoidinconsistent interface assumptions
executables skip ocamldep)
Reproduction case from @art-w.
Ref: #4572
Test plan
main(no filtering active, all deps present)