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test: cross-library .cmi regression baselines (4 fixtures)#14584

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robinbb-test-cross-lib-soundness-barriers
May 27, 2026
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test: cross-library .cmi regression baselines (4 fixtures)#14584
Alizter merged 1 commit into
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robinbb-test-cross-lib-soundness-barriers

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@robinbb robinbb commented May 18, 2026

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Four fixtures pinning the consumer-compile cmi-dep behaviour today, when the cctx-wide cmi glob over a dep lib's objdir covers the consumer's transitive .cmi needs regardless of whether ocamldep can see the chain syntactically. Each fixture hides the leaf's name from ocamldep through a different mechanism:

  • cross-lib-preprocess-barrier.t — (preprocess (action ...))
  • cross-lib-pps-runtime-no-ocamldep-barrier.t — (preprocess (pps X)) + ppx_runtime_libraries
  • cross-lib-instrumentation-barrier.t — (instrumentation (backend X))
  • cross-lib-open-flag-barrier.t — (flags (-open M))

Three of the four assert build success under --sandbox=copy. The instrumentation case additionally pins today's wide cmi glob over middle's objdir in dune rules output.

The forthcoming per-module narrowing work (#14492) will validate that each construct continues to work soundly under tighter per-module dep tracking, and will flip the instrumentation case's jq expected output from "glob present" to "glob absent".

@robinbb robinbb force-pushed the robinbb-test-cross-lib-soundness-barriers branch 2 times, most recently from 7e57b43 to 1b7d59d Compare May 18, 2026 18:02
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@robinbb robinbb self-assigned this May 18, 2026
@robinbb robinbb force-pushed the robinbb-test-cross-lib-soundness-barriers branch from 1b7d59d to 3c4514f Compare May 18, 2026 20:31
@robinbb robinbb requested a review from Copilot May 18, 2026 20:36
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Pull request overview

Adds blackbox regression fixtures under per-module-lib-deps/ to pin today’s “wide .cmi glob” behavior for cross-library compilation dependencies in cases where ocamldep can’t see the full transitive .cmi chain (preprocess/action, ppx runtime deps, instrumentation backend, and -open flags). These baselines are intended to guard upcoming per-module dependency narrowing work (#14492).

Changes:

  • Add a preprocess (action ...) fixture ensuring a consumer build succeeds under --sandbox=copy when only transitive .cmi loads make the leaf needed.
  • Add a ppx runtime-libraries fixture ensuring the consumer build succeeds under --sandbox=copy even when the runtime library is never named in consumer source.
  • Add an instrumentation-backend fixture that snapshots the current .cmi glob present in dune rules JSON output.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

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File Description
test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-preprocess-barrier.t New blackbox test for .cmi dep tracking across an action-preprocessed library under sandbox copy.
test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-pps-runtime-no-ocamldep-barrier.t/run.t New blackbox test exercising ppx_runtime_libraries-induced compile-time .cmi needs under sandbox copy.
test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-instrumentation-barrier.t/run.t New blackbox test pinning current instrumentation-disabled behavior and .cmi glob presence in dune rules output.
test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-instrumentation-barrier.t/ppx/hello.ml Support library for the instrumentation backend fixture.
test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-instrumentation-barrier.t/ppx/hello_ppx.ml Support ppx rewriter for the instrumentation backend fixture.
test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-instrumentation-barrier.t/ppx/dune-project Defines the nested hello package for the instrumentation backend fixture.
test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-instrumentation-barrier.t/ppx/dune Declares the instrumentation backend and its ppx/runtime library.
test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-open-flag-barrier.t New blackbox test intended to cover -open-hidden transitive .cmi needs under sandbox copy.

Comment thread test/blackbox-tests/test-cases/per-module-lib-deps/cross-lib-open-flag-barrier.t
@robinbb robinbb force-pushed the robinbb-test-cross-lib-soundness-barriers branch from 3c4514f to 3fb5e95 Compare May 18, 2026 20:57
@robinbb robinbb marked this pull request as ready for review May 18, 2026 22:11
@robinbb robinbb requested a review from Alizter May 18, 2026 22:11
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robinbb commented May 18, 2026

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@Alizter This is more code that I have factored out of the 9-layer PR 14492.

@robinbb robinbb force-pushed the robinbb-test-cross-lib-soundness-barriers branch from 3fb5e95 to 6b999b2 Compare May 18, 2026 23:17
@robinbb robinbb requested a review from Alizter May 18, 2026 23:18
@robinbb
test: cross-library .cmi regression baselines (4 fixtures)
7e326e9 
Four fixtures pinning the consumer-compile cmi-dep behaviour today, when the cctx-wide cmi glob over a dep lib's objdir covers the consumer's transitive `.cmi` needs regardless of whether `ocamldep` can see the chain syntactically. Each fixture hides the leaf's name from `ocamldep` through a different mechanism:

- `cross-lib-preprocess-barrier.t` — `(preprocess (action ...))`
- `cross-lib-pps-runtime-no-ocamldep-barrier.t` — `(preprocess (pps X))` + `ppx_runtime_libraries`
- `cross-lib-instrumentation-barrier.t` — `(instrumentation (backend X))`
- `cross-lib-open-flag-barrier.t` — `(flags (-open M))`

Three of the four assert build success under `--sandbox=copy`. The instrumentation case additionally pins today's wide cmi glob over `middle`'s objdir in `dune rules` output.

The forthcoming per-module narrowing work (#14492) will validate that each construct continues to work soundly under tighter per-module dep tracking, and will flip the instrumentation case's `jq` expected output from "glob present" to "glob absent".

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
@robinbb robinbb force-pushed the robinbb-test-cross-lib-soundness-barriers branch from 6b999b2 to 7e326e9 Compare May 20, 2026 20:33
@Alizter Alizter merged commit 4e6677b into main May 27, 2026
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@Alizter Alizter deleted the robinbb-test-cross-lib-soundness-barriers branch May 27, 2026 19:39
@robinbb robinbb mentioned this pull request May 29, 2026
Merged
robinbb added a commit to robinbb/dune that referenced this pull request May 29, 2026
@robinbb
fix: BFS-expand through dep libs' effective -open modules
f6294d5 
Closes a soundness gap in the per-module narrowing pipeline missed
by the wrapped / ppx-runtime / virtual-impl recoveries: when a
dependency library's effective flags inject [-open M], its source
can reference [M]'s identifiers without naming [M], and ocamldep
emits no token to drive the cross-library walker. Both the
library stanza's own [(flags ...)] and any [(env ...)] stanza that
contributes default flags to the dep lib's directory can inject
[-open] entries.

Reported by RyanJamesStewart on ocaml#14517 with this fixture: an
unwrapped [middle] depending on unwrapped [prelude] with
[(flags (:standard -open Prelude))], exposing
[val pick : unit -> color] (where [color] resolves through the open
to [Prelude.color]). The consumer pattern-matches the result
against bare constructors. The compile genuinely needs [prelude.cmi]
to resolve the constructors; the BFS over [ocamldep -modules]
cannot reach [prelude] (no syntactic [Prelude] token on either
side); the three existing recoveries do not catch it ([prelude] is
not wrapped, not a ppx-runtime lib, not a virtual-impl).

[Module_compilation.cross_lib_tight_set]:
- Add [~mode] (the consumer's compile mode) so we can expand a dep
  lib's effective flags via [Ocaml_flags.get].
- Extend [read_entry_deps] to compute [read_lib_opens] for the
  visited lib and union the result into the BFS frontier. Localised
  in the BFS rather than the initial-frontier computation so the
  reachability rule reads as: a module is reachable iff the consumer
  references it, or some reached module's ocamldep names it, or some
  reached module's owning lib's effective flags open it.
- [read_lib_opens] short-circuits to empty for non-local libs; their
  [src_dir] is not a build path, and env stanzas cannot inject flags
  into already-compiled artifacts. For local libs we evaluate
  [Ocaml_flags_db.ocaml_flags] which folds env-stanza flags under the
  library stanza's spec, so both injection paths are captured even
  when the library stanza is [:standard].

[Lib_info]:
- Add [stanza_flags : Dune_lang.Ocaml_flags.Spec.t] field plus
  accessor. Local libs carry their stanza's [conf.buildable.flags];
  external libs ([findlib], [dune_package]) carry [Spec.standard].

Regression tests on `main` that this patch makes pass under the
per-module narrowing stack:
- [cross-lib-open-flag-barrier.t] (added by ocaml#14584) pins the
  stanza-flag injection path. Fails on L4 and L5 head before this
  patch (Unbound constructor Green under [--sandbox=copy]); passes
  after.
- [cross-lib-env-open-flag-barrier.t] (added by ocaml#14776) pins the
  env-stanza injection path: same shape, but [-open Prelude] is
  supplied by an [(env ...)] stanza while the library stanza uses
  [:standard]. Fails on the pre-ocaml#14517 [:standard]-short-circuit
  variant of this patch (same Unbound constructor error); passes
  after.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
Alizter pushed a commit that referenced this pull request May 30, 2026
@robinbb
test: env-stanza -open variant of cross-lib .cmi regression baseline
aa9415d 
Fifth fixture in the cross-lib `.cmi` regression baseline family
(#14584): pins consumer-compile cmi-dep behaviour when `-open M`
is injected by an `(env ...)` stanza rather than the intermediate
library's own `(flags ...)` field. The intermediate's library
stanza uses `:standard`. Asserts build success under
`--sandbox=copy`.

The forthcoming per-module narrowing work (#14492) will validate
that this construct continues to work soundly under tighter
per-module dep tracking.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
Alizter added a commit that referenced this pull request May 30, 2026
@Alizter
test: env-stanza -open variant of cross-lib .cmi regression baseline (#…
6d7951f 
…14776)

## Summary

Fifth fixture in the cross-lib `.cmi` regression baseline family started
by #14584. Pins consumer-compile `.cmi` dep behaviour when `-open M` is
injected by an `(env ...)` stanza rather than the intermediate library's
own `(flags ...)` field. The intermediate's library stanza uses
`:standard`. Asserts build success under `--sandbox=copy`.

Pairs with the stanza-flag variant `cross-lib-open-flag-barrier.t`
already on `main` from #14584, covering the second of the two `-open`
injection paths.

The forthcoming per-module narrowing work (#14492) will validate that
this construct continues to work soundly under tighter per-module dep
tracking.
robinbb added a commit that referenced this pull request Jun 8, 2026
@robinbb
fix: BFS-expand through dep libs' effective -open modules
f310a37 
Closes a soundness gap in the per-module narrowing pipeline missed
by the wrapped / ppx-runtime / virtual-impl recoveries: when a
dependency library's effective flags inject [-open M], its source
can reference [M]'s identifiers without naming [M], and ocamldep
emits no token to drive the cross-library walker. Both the
library stanza's own [(flags ...)] and any [(env ...)] stanza that
contributes default flags to the dep lib's directory can inject
[-open] entries.

Reported by RyanJamesStewart on #14517 with this fixture: an
unwrapped [middle] depending on unwrapped [prelude] with
[(flags (:standard -open Prelude))], exposing
[val pick : unit -> color] (where [color] resolves through the open
to [Prelude.color]). The consumer pattern-matches the result
against bare constructors. The compile genuinely needs [prelude.cmi]
to resolve the constructors; the BFS over [ocamldep -modules]
cannot reach [prelude] (no syntactic [Prelude] token on either
side); the three existing recoveries do not catch it ([prelude] is
not wrapped, not a ppx-runtime lib, not a virtual-impl).

[Module_compilation.cross_lib_tight_set]:
- Add [~mode] (the consumer's compile mode) so we can expand a dep
  lib's effective flags via [Ocaml_flags.get].
- Extend [read_entry_deps] to compute [read_lib_opens] for the
  visited lib and union the result into the BFS frontier. Localised
  in the BFS rather than the initial-frontier computation so the
  reachability rule reads as: a module is reachable iff the consumer
  references it, or some reached module's ocamldep names it, or some
  reached module's owning lib's effective flags open it.
- [read_lib_opens] short-circuits to empty for non-local libs; their
  [src_dir] is not a build path, and env stanzas cannot inject flags
  into already-compiled artifacts. For local libs we evaluate
  [Ocaml_flags_db.ocaml_flags] which folds env-stanza flags under the
  library stanza's spec, so both injection paths are captured even
  when the library stanza is [:standard].

[Lib_info]:
- Add [stanza_flags : Dune_lang.Ocaml_flags.Spec.t] field plus
  accessor. Local libs carry their stanza's [conf.buildable.flags];
  external libs ([findlib], [dune_package]) carry [Spec.standard].

Regression tests on `main` that this patch makes pass under the
per-module narrowing stack:
- [cross-lib-open-flag-barrier.t] (added by #14584) pins the
  stanza-flag injection path. Fails on L4 and L5 head before this
  patch (Unbound constructor Green under [--sandbox=copy]); passes
  after.
- [cross-lib-env-open-flag-barrier.t] (added by #14776) pins the
  env-stanza injection path: same shape, but [-open Prelude] is
  supplied by an [(env ...)] stanza while the library stanza uses
  [:standard]. Fails on the pre-#14517 [:standard]-short-circuit
  variant of this patch (same Unbound constructor error); passes
  after.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
@robinbb robinbb mentioned this pull request Jun 8, 2026
Merged
robinbb added a commit that referenced this pull request Jun 8, 2026
@robinbb
fix: BFS-expand through dep libs' effective -open modules
95b35de 
Closes a soundness gap in the per-module narrowing pipeline missed
by the wrapped / ppx-runtime / virtual-impl recoveries: when a
dependency library's effective flags inject [-open M], its source
can reference [M]'s identifiers without naming [M], and ocamldep
emits no token to drive the cross-library walker. Both the
library stanza's own [(flags ...)] and any [(env ...)] stanza that
contributes default flags to the dep lib's directory can inject
[-open] entries.

Reported by RyanJamesStewart on #14517 with this fixture: an
unwrapped [middle] depending on unwrapped [prelude] with
[(flags (:standard -open Prelude))], exposing
[val pick : unit -> color] (where [color] resolves through the open
to [Prelude.color]). The consumer pattern-matches the result
against bare constructors. The compile genuinely needs [prelude.cmi]
to resolve the constructors; the BFS over [ocamldep -modules]
cannot reach [prelude] (no syntactic [Prelude] token on either
side); the three existing recoveries do not catch it ([prelude] is
not wrapped, not a ppx-runtime lib, not a virtual-impl).

[Module_compilation.cross_lib_tight_set]:
- Add [~mode] (the consumer's compile mode) so we can expand a dep
  lib's effective flags via [Ocaml_flags.get].
- Extend [read_entry_deps] to compute [read_lib_opens] for the
  visited lib and union the result into the BFS frontier. Localised
  in the BFS rather than the initial-frontier computation so the
  reachability rule reads as: a module is reachable iff the consumer
  references it, or some reached module's ocamldep names it, or some
  reached module's owning lib's effective flags open it.
- [read_lib_opens] short-circuits to empty for non-local libs; their
  [src_dir] is not a build path, and env stanzas cannot inject flags
  into already-compiled artifacts. For local libs we evaluate
  [Ocaml_flags_db.ocaml_flags] which folds env-stanza flags under the
  library stanza's spec, so both injection paths are captured even
  when the library stanza is [:standard].

[Lib_info]:
- Add [stanza_flags : Dune_lang.Ocaml_flags.Spec.t] field plus
  accessor. Local libs carry their stanza's [conf.buildable.flags];
  external libs ([findlib], [dune_package]) carry [Spec.standard].

Regression tests on `main` that this patch makes pass under the
per-module narrowing stack:
- [cross-lib-open-flag-barrier.t] (added by #14584) pins the
  stanza-flag injection path. Fails on L4 and L5 head before this
  patch (Unbound constructor Green under [--sandbox=copy]); passes
  after.
- [cross-lib-env-open-flag-barrier.t] (added by #14776) pins the
  env-stanza injection path: same shape, but [-open Prelude] is
  supplied by an [(env ...)] stanza while the library stanza uses
  [:standard]. Fails on the pre-#14517 [:standard]-short-circuit
  variant of this patch (same Unbound constructor error); passes
  after.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
robinbb added a commit to robinbb/dune that referenced this pull request Jun 8, 2026
@robinbb
test: cross-library .cmi baseline for dotted -open path
c419eaf 
A fifth sibling to the cross-library `.cmi` regression baselines (ocaml#14584), covering `(flags (-open Prelude.Color))` where the intermediate library opens a *dotted* module path naming a submodule of a wrapped dependency, rather than a bare top-level module.

As in `cross-lib-open-flag-barrier.t`, the intermediate's source never names `Prelude` (the open hides it) and the consumer never names it either, so `ocamldep` sees no syntactic chain to `prelude`. The fixture asserts build success under `--sandbox=copy`, pinning that the consumer's compile tracks `prelude`'s `.cmi`s.

The forthcoming per-module narrowing work (ocaml#14492) must key its effective-`-open` detection on the head component of the path (`Prelude` from `Prelude.Color`), since only top-level module names map to libraries; without that, the dotted open would be dropped from the cross-library frontier and the sandboxed build would regress.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
robinbb added a commit that referenced this pull request Jun 8, 2026
@robinbb
test: cross-library .cmi baseline for dotted -open path
7347d71 
A fifth sibling to the cross-library `.cmi` regression baselines (#14584), covering `(flags (-open Prelude.Color))` where the intermediate library opens a *dotted* module path naming a submodule of a wrapped dependency, rather than a bare top-level module.

As in `cross-lib-open-flag-barrier.t`, the intermediate's source never names `Prelude` (the open hides it) and the consumer never names it either, so `ocamldep` sees no syntactic chain to `prelude`. The fixture asserts build success under `--sandbox=copy`, pinning that the consumer's compile tracks `prelude`'s `.cmi`s.

The forthcoming per-module narrowing work (#14492) must key its effective-`-open` detection on the head component of the path (`Prelude` from `Prelude.Color`), since only top-level module names map to libraries; without that, the dotted open would be dropped from the cross-library frontier and the sandboxed build would regress.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
robinbb added a commit that referenced this pull request Jun 8, 2026
@robinbb
fix: BFS-expand through dep libs' effective -open modules
72c3f1a 
Closes a soundness gap in the per-module narrowing pipeline missed
by the wrapped / ppx-runtime / virtual-impl recoveries: when a
dependency library's effective flags inject [-open M], its source
can reference [M]'s identifiers without naming [M], and ocamldep
emits no token to drive the cross-library walker. Both the
library stanza's own [(flags ...)] and any [(env ...)] stanza that
contributes default flags to the dep lib's directory can inject
[-open] entries.

Reported by RyanJamesStewart on #14517 with this fixture: an
unwrapped [middle] depending on unwrapped [prelude] with
[(flags (:standard -open Prelude))], exposing
[val pick : unit -> color] (where [color] resolves through the open
to [Prelude.color]). The consumer pattern-matches the result
against bare constructors. The compile genuinely needs [prelude.cmi]
to resolve the constructors; the BFS over [ocamldep -modules]
cannot reach [prelude] (no syntactic [Prelude] token on either
side); the three existing recoveries do not catch it ([prelude] is
not wrapped, not a ppx-runtime lib, not a virtual-impl).

[Module_compilation.cross_lib_tight_set]:
- Add [~mode] (the consumer's compile mode) so we can expand a dep
  lib's effective flags via [Ocaml_flags.get].
- Extend [read_entry_deps] to compute [read_lib_opens] for the
  visited lib and union the result into the BFS frontier. Localised
  in the BFS rather than the initial-frontier computation so the
  reachability rule reads as: a module is reachable iff the consumer
  references it, or some reached module's ocamldep names it, or some
  reached module's owning lib's effective flags open it.
- [read_lib_opens] short-circuits to empty for non-local libs; their
  [src_dir] is not a build path, and env stanzas cannot inject flags
  into already-compiled artifacts. For local libs we evaluate
  [Ocaml_flags_db.ocaml_flags] which folds env-stanza flags under the
  library stanza's spec, so both injection paths are captured even
  when the library stanza is [:standard].

[Lib_info]:
- Add [stanza_flags : Dune_lang.Ocaml_flags.Spec.t] field plus
  accessor. Local libs carry their stanza's [conf.buildable.flags];
  external libs ([findlib], [dune_package]) carry [Spec.standard].

Regression tests on `main` that this patch makes pass under the
per-module narrowing stack:
- [cross-lib-open-flag-barrier.t] (added by #14584) pins the
  stanza-flag injection path. Fails on L4 and L5 head before this
  patch (Unbound constructor Green under [--sandbox=copy]); passes
  after.
- [cross-lib-env-open-flag-barrier.t] (added by #14776) pins the
  env-stanza injection path: same shape, but [-open Prelude] is
  supplied by an [(env ...)] stanza while the library stanza uses
  [:standard]. Fails on the pre-#14517 [:standard]-short-circuit
  variant of this patch (same Unbound constructor error); passes
  after.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
robinbb added a commit to robinbb/dune that referenced this pull request Jun 8, 2026
@robinbb
test: cross-library .cmi baseline for chained -open path
ab6a151 
A sibling to the cross-library `.cmi` regression baselines (ocaml#14584), covering two chained opens `(flags (-open Prelude -open Color))` where the second argument resolves through the first: `Color` is the `Color` submodule of the wrapped dependency `prelude`, brought into scope by `-open Prelude`, not a top-level module.

As in `cross-lib-open-flag-barrier.t`, the intermediate's source names neither `Prelude` nor `Color`, so `ocamldep` sees no syntactic chain to `prelude`. The fixture asserts build success under `--sandbox=copy`, pinning that the consumer's compile tracks `prelude`'s `.cmi`s.

Per-module narrowing (ocaml#14492) must stay sound when an `-open` argument is not a compilation unit: here `-open Prelude` already reaches `prelude`, covering `Color`'s contents.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
robinbb added a commit that referenced this pull request Jun 8, 2026
@robinbb
test: cross-library .cmi baseline for chained -open path
fd63b53 
A sibling to the cross-library `.cmi` regression baselines (#14584), covering two chained opens `(flags (-open Prelude -open Color))` where the second argument resolves through the first: `Color` is the `Color` submodule of the wrapped dependency `prelude`, brought into scope by `-open Prelude`, not a top-level module.

As in `cross-lib-open-flag-barrier.t`, the intermediate's source names neither `Prelude` nor `Color`, so `ocamldep` sees no syntactic chain to `prelude`. The fixture asserts build success under `--sandbox=copy`, pinning that the consumer's compile tracks `prelude`'s `.cmi`s.

Per-module narrowing (#14492) must stay sound when an `-open` argument is not a compilation unit: here `-open Prelude` already reaches `prelude`, covering `Color`'s contents.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
robinbb added a commit that referenced this pull request Jun 8, 2026
@robinbb
fix: BFS-expand through dep libs' effective -open modules
fcbc236 
Closes a soundness gap in the per-module narrowing pipeline missed
by the wrapped / ppx-runtime / virtual-impl recoveries: when a
dependency library's effective flags inject [-open M], its source
can reference [M]'s identifiers without naming [M], and ocamldep
emits no token to drive the cross-library walker. Both the
library stanza's own [(flags ...)] and any [(env ...)] stanza that
contributes default flags to the dep lib's directory can inject
[-open] entries.

Reported by RyanJamesStewart on #14517 with this fixture: an
unwrapped [middle] depending on unwrapped [prelude] with
[(flags (:standard -open Prelude))], exposing
[val pick : unit -> color] (where [color] resolves through the open
to [Prelude.color]). The consumer pattern-matches the result
against bare constructors. The compile genuinely needs [prelude.cmi]
to resolve the constructors; the BFS over [ocamldep -modules]
cannot reach [prelude] (no syntactic [Prelude] token on either
side); the three existing recoveries do not catch it ([prelude] is
not wrapped, not a ppx-runtime lib, not a virtual-impl).

[Module_compilation.cross_lib_tight_set]:
- Add [~mode] (the consumer's compile mode) so we can expand a dep
  lib's effective flags via [Ocaml_flags.get].
- Extend [read_entry_deps] to compute [read_lib_opens] for the
  visited lib and union the result into the BFS frontier. Localised
  in the BFS rather than the initial-frontier computation so the
  reachability rule reads as: a module is reachable iff the consumer
  references it, or some reached module's ocamldep names it, or some
  reached module's owning lib's effective flags open it.
- [read_lib_opens] short-circuits to empty for non-local libs; their
  [src_dir] is not a build path, and env stanzas cannot inject flags
  into already-compiled artifacts. For local libs we evaluate
  [Ocaml_flags_db.ocaml_flags] which folds env-stanza flags under the
  library stanza's spec, so both injection paths are captured even
  when the library stanza is [:standard].

[Lib_info]:
- Add [stanza_flags : Dune_lang.Ocaml_flags.Spec.t] field plus
  accessor. Local libs carry their stanza's [conf.buildable.flags];
  external libs ([findlib], [dune_package]) carry [Spec.standard].

Regression tests on `main` that this patch makes pass under the
per-module narrowing stack:
- [cross-lib-open-flag-barrier.t] (added by #14584) pins the
  stanza-flag injection path. Fails on L4 and L5 head before this
  patch (Unbound constructor Green under [--sandbox=copy]); passes
  after.
- [cross-lib-env-open-flag-barrier.t] (added by #14776) pins the
  env-stanza injection path: same shape, but [-open Prelude] is
  supplied by an [(env ...)] stanza while the library stanza uses
  [:standard]. Fails on the pre-#14517 [:standard]-short-circuit
  variant of this patch (same Unbound constructor error); passes
  after.

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
robinbb added a commit that referenced this pull request Jun 9, 2026
@robinbb
test: cross-library .cmi baseline for dotted -open path (#15056)
19568fd 
## Summary

A fifth sibling to the cross-library `.cmi` regression baselines from
#14584, covering an intermediate library compiled with `(flags (-open
Prelude.Color))` — a *dotted* module path naming a submodule of a
wrapped dependency, rather than a bare top-level module.

The fixture asserts build success under `--sandbox=copy`. It builds on
`main` today (no per-module narrowing) and pins behaviour that the
per-module narrowing work in #14492 must preserve: the effective-`-open`
detection has to key on the head component of the path (`Prelude` from
`Prelude.Color`), since only top-level module names map to libraries.
Without that, the dotted open is dropped from the cross-library frontier
and the sandboxed build regresses.

Test-only; no changelog.

---------

Signed-off-by: Robin Bate Boerop <me@robinbb.com>
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