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test: sibling-module consumer unreferenced-dep regression guard #14309

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robinbb merged 2 commits into from
Apr 27, 2026
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test: sibling-module consumer unreferenced-dep regression guard #14309

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test: add sibling-module consumer unreferenced-dep regression guard
robinbb Apr 23, 2026
855d030
test: rewrite as observational baseline with signature-change edit
robinbb Apr 23, 2026
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76 changes: 76 additions & 0 deletions test/blackbox-tests/test-cases/per-module-lib-deps/sibling-unreferenced-lib.t
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Baseline: multi-module consumer library with a sibling module that
references no module of its declared dependency library.

This is an observational test. It records the number of rebuild
targets for the consumer's [spurious_rebuild] module when a module
of the dependency library [dep_lib] has its interface edited.

[consumer_lib] is an unwrapped library with two modules.
[consumes_dep] references [Referenced_dep]; [spurious_rebuild]
references nothing from [dep_lib]. On current main, editing
[referenced_dep]'s interface rebuilds [spurious_rebuild] even
though it references nothing from [dep_lib]: the consumer depends
on a glob over [dep_lib]'s object directory, which is invalidated
by the cmi change.

The zero-reference-sibling-in-a-library corner is distinct from
scenarios covered by existing tests: [lib-to-lib-unwrapped.t] probes
siblings that reference a different (non-edited) module of the dep;
[transitive.t] and [unwrapped.t] probe zero-reference modules but
within executable stanzas, not library stanzas. A future fix
implementing library-level dep filtering at consumer-module
granularity would drop [dep_lib] entirely from [spurious_rebuild]'s
deps, tightening this corner to zero rebuilds.

See: https://github.com/ocaml/dune/issues/4572
See: https://github.com/ocaml/dune/pull/14116#issuecomment-4301275263

$ cat > dune-project <<EOF
> (lang dune 3.23)
> EOF

$ cat > dune <<EOF
> (library
> (name dep_lib)
> (wrapped false)
> (modules unused_module referenced_dep))
> (library
> (name consumer_lib)
> (wrapped false)
> (modules consumes_dep spurious_rebuild)
> (libraries dep_lib))
> EOF

$ cat > unused_module.ml <<EOF
> let x = 42
> EOF
$ cat > referenced_dep.ml <<EOF
> let x = 43
> EOF
$ cat > referenced_dep.mli <<EOF
> val x : int
> EOF
$ cat > consumes_dep.ml <<EOF
> let x = Referenced_dep.x
> EOF
$ cat > spurious_rebuild.ml <<EOF
> let x = 12
> EOF

$ dune build @check

Edit [referenced_dep]'s interface. [spurious_rebuild] references
nothing in [dep_lib]. Record the number of [spurious_rebuild]
rebuild targets observed in the trace:

$ cat > referenced_dep.mli <<EOF
> val x : int
> val y : string
> EOF
$ cat > referenced_dep.ml <<EOF
> let x = 43
> let y = "hello"
> EOF
$ dune build @check
$ dune trace cat | jq -s 'include "dune"; [.[] | targetsMatchingFilter(test("spurious_rebuild"))] | length'
1
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