test: enabled_if in foreign_library not respected

doc/changes/11707.md

@@ -0,0 +1,2 @@
+- fix: Evaluate `enabled_if` when computing the stubs for stanzas such as
+  `foreign_library` (#11707, @Alizter, @rgrinberg)

src/dune_rules/dir_contents.ml

@@ -292,7 +292,7 @@ end = struct
               ; foreign_sources =
                   Memo.lazy_ (fun () ->
                     let dune_version = Dune_project.dune_version project in
-                    stanzas >>| Foreign_sources.make ~dune_version ~dirs)
+                    stanzas >>= Foreign_sources.make ~dir ~dune_version ~dirs)
               ; coq =
                   Memo.lazy_ (fun () ->
                     stanzas >>| Coq_sources.of_dir ~dir ~include_subdirs ~dirs)
@@ -370,7 +370,7 @@ end = struct
            let foreign_sources =
              Memo.lazy_ (fun () ->
                let dune_version = Dune_project.dune_version project in
-               stanzas >>| Foreign_sources.make ~dune_version ~dirs)
+               stanzas >>= Foreign_sources.make ~dir ~dune_version ~dirs)
            in
            let coq =
              Memo.lazy_ (fun () ->

src/dune_rules/foreign_sources.ml

@@ -1,4 +1,5 @@
 open Import
+open Memo.O
 
 type t =
   { libraries : Foreign.Sources.t Lib_name.Map.t
@@ -215,24 +216,23 @@ let make stanzas ~(sources : Unresolved.t) ~dune_version =
       List.fold_left
         stanzas
         ~init:([], [], [])
-        ~f:(fun ((libs, foreign_libs, exes) as acc) stanza ->
-          match Stanza.repr stanza with
-          | Library.T lib ->
+        ~f:(fun (libs, foreign_libs, exes) stanza ->
+          match stanza with
+          | `Library (lib : Library.t) ->
             let all =
               eval_foreign_stubs lib.buildable.foreign_stubs lib.buildable.ctypes
             in
             (lib, all) :: libs, foreign_libs, exes
-          | Foreign_library.T library ->
+          | `Foreign_library (library : Foreign_library.t) ->
             let all = eval_foreign_stubs [ library.stubs ] None in
             ( libs
             , (library.archive_name, (library.archive_name_loc, all)) :: foreign_libs
             , exes )
-          | Executables.T exe | Tests.T { exes = exe; _ } ->
+          | `Executables exe | `Tests { Tests.exes = exe; _ } ->
             let all =
               eval_foreign_stubs exe.buildable.foreign_stubs exe.buildable.ctypes
             in
-            libs, foreign_libs, (exe, all) :: exes
-          | _ -> acc)
+            libs, foreign_libs, (exe, all) :: exes)
     in
     List.(rev libs, rev foreign_libs, rev exes)
   in
@@ -337,3 +337,23 @@ let make stanzas ~dune_version ~dirs =
   let sources = Unresolved.load_dirs ~dune_version dirs in
   make stanzas ~dune_version ~sources
 ;;
+
+let make stanzas ~dir ~dune_version ~dirs =
+  let+ stanzas =
+    List.filter_map stanzas ~f:(fun stanza ->
+      match Stanza.repr stanza with
+      | Library.T lib -> Some (`Library lib, lib.enabled_if)
+      | Foreign_library.T lib -> Some (`Foreign_library lib, lib.enabled_if)
+      | Executables.T exe -> Some (`Executables exe, exe.enabled_if)
+      | Tests.T ({ exes = exe; _ } as tests) -> Some (`Tests tests, exe.enabled_if)
+      | _ -> None)
+    |> Memo.parallel_map ~f:(fun (stanza, enabled_if) ->
+      let* expander = Expander0.get ~dir in
+      Expander0.eval_blang expander enabled_if
+      >>| function
+      | false -> None
+      | true -> Some stanza)
+    >>| List.filter_opt
+  in
+  make stanzas ~dune_version ~dirs
+;;

src/dune_rules/foreign_sources.mli

@@ -11,6 +11,7 @@ val for_exes : t -> first_exe:string -> Foreign.Sources.t
 
 val make
   :  Stanza.t list
+  -> dir:Path.Build.t
   -> dune_version:Syntax.Version.t
   -> dirs:Source_file_dir.t list
-  -> t
+  -> t Memo.t

test/blackbox-tests/test-cases/foreign-stubs/foreign-library-enabled-if.t

@@ -0,0 +1,64 @@
+Interaction of the foreign_library stanza and the enabled_if field.
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.18)
+  > EOF
+
+We should allow multiple foreign libraries to define the same archive if only
+one of them is enabled:
+
+  $ cat > dune <<EOF
+  > (foreign_library
+  >  (enabled_if true)
+  >  (language c)
+  >  (archive_name a)
+  >  (names a))
+  > 
+  > (foreign_library
+  >  (enabled_if false)
+  >  (language c)
+  >  (archive_name a)
+  >  (names a))
+  > 
+  > (foreign_library
+  >  (enabled_if false)
+  >  (language c)
+  >  (archive_name a)
+  >  (names a))
+  > EOF
+  $ cat > a.c
+  $ dune build
+
+
+Repeat the test, but now two of the libraries are indeed enabled which is
+illegal:
+
+  $ cat > dune <<EOF
+  > (foreign_library
+  >  (enabled_if true)
+  >  (language c)
+  >  (archive_name a)
+  >  (names a))
+  > 
+  > (foreign_library
+  >  (enabled_if true)
+  >  (language c)
+  >  (archive_name a)
+  >  (names a))
+  > 
+  > (foreign_library
+  >  (enabled_if false)
+  >  (language c)
+  >  (archive_name a)
+  >  (names a))
+  > EOF
+  $ cat > a.c
+  $ dune build
+  File "dune", line 5, characters 8-9:
+  5 |  (names a))
+              ^
+  Error: Multiple definitions for the same object file "a". See another
+  definition at dune:11.
+  Hint: You can avoid the name clash by renaming one of the objects, or by
+  placing it into a different directory.
+  [1]

test/blackbox-tests/test-cases/foreign-stubs/github10675.t

@@ -20,8 +20,3 @@ stubs, dune should not crash. See #10675.
   $ touch startup.c main.ml
 
   $ dune build
-  File "dune", line 3, characters 7-11:
-  3 |  (name main))
-             ^^^^
-  Error: Executables with same name "main" use different foreign sources
-  [1]