Fix separate installation of implementations

When instantiating an implementation with a variant, make sure it matches vlib's
known implementations. It replaces the same-project check that was done when
instantiating an implementation.

Signed-off-by: Lucas Pluvinage <lucas.pluvinage@gmail.com>

CHANGES.md

@@ -14,6 +14,10 @@
 1.11.0 (unreleased)
 -------------------
 
+- When instantiating an implementation with a variant, make sure it matches
+  virtual library's list of known implementations. (..., fixes #2322, @TheLortex,
+  review by ...)
+
 - Don't reserve the `Ppx` toplevel module name for ppx rewriters (#2242, @diml)
 
 - Redesign of the library variant feature according to the #2134 proposal. The

src/lib.ml

@@ -168,6 +168,28 @@ module Error = struct
           (Lib_name.to_string not_vlib)
           (Lib_name.to_string impl)
       ]
+
+  let vlib_known_implementation_mismatch ~loc ~name ~variant ~vlib_name =
+    make ~loc
+      [
+        Pp.textf "Virtual library %S doesn't know about implementation %S with \
+                  variant %S. Instead of using (variant %s) here, you need to \
+                  reference it in the virtual library project, using the \
+                  external_variant stanza:\n\
+                  (external_variant\n\
+                  \  (virtual_library %s)\n\
+                  \  (variant %s)\n\
+                  \  (implementation %s))"
+          (Lib_name.to_string vlib_name)
+          (Lib_name.to_string name)
+          (Variant.to_string variant)
+          (Variant.to_string variant)
+          (Lib_name.to_string vlib_name)
+          (Variant.to_string variant)
+          (Lib_name.to_string name)
+      ]
+
+
 end
 
 (* Types *)
@@ -864,32 +886,19 @@ let rec instantiate db name info ~stack ~hidden =
         | None -> Ok vlib
         | Some variant ->
           (* If the library is an implementation tagged with a
-             variant, we must make sure that that it implements a
-             library that is part of the same project *)
-          let status_vlib = Lib_info.status vlib.info in
-          if Option.equal Dune_project.Name.equal
-               (Lib_info.Status.project_name status)
-               (Lib_info.Status.project_name status_vlib)
-          then
-            Ok vlib
-          else
+             variant, we must make sure that that it's correctly part of the
+             virtual library's known implementations. *)
+          let vlib_impls = Lib_info.known_implementations vlib.info in
+          Variant.Map.find vlib_impls variant
+          |> Option.bind
+            ~f:(fun (_, impl_name) ->
+              let name = Lib_info.name info in
+              Option.some_if (Lib_name.equal impl_name name) (Ok vlib))
+          |> Option.value
+          ~default:(
+            let vlib_name = Lib_info.name vlib.info in
             let name = Lib_info.name info in
-            let name_vlib = Lib_info.name vlib.info in
-            Errors.fail loc
-              "Library implementation %a with variant %a implements@ a \
-               library outside the project.@ Instead of using \
-               (variant %a) here,@ you need to reference it in the \
-               virtual library project,@ using the external_variant stanza:@ \
-               (external_variant@\n\
-               \  (virtual_library %a)@\n\
-               \  (variant %a)@\n\
-               \  (implementation %a))"
-              Lib_name.pp name
-              Variant.pp variant
-              Variant.pp variant
-              Lib_name.pp name_vlib
-              Variant.pp variant
-              Lib_name.pp name)
+            Error.vlib_known_implementation_mismatch ~loc ~name ~variant ~vlib_name))
   in
   let default_implementation =
     Lib_info.default_implementation info

test/blackbox-tests/test-cases/variants-multi-project/run.t

@@ -5,12 +5,12 @@ variant.
   File "prj2/dune", line 4, characters 13-20:
   4 |  (implements vlibfoo)
                    ^^^^^^^
-  Error: Library implementation impl with variant "somevariant" implements
-  a library outside the project. Instead of using (variant "somevariant") here,
-  you need to reference it in the virtual library project,
-  using the external_variant stanza:
+  Error: Virtual library "vlibfoo" doesn't know about implementation "impl"
+  with variant "somevariant". Instead of using (variant somevariant) here, you
+  need to reference it in the virtual library project, using the
+  external_variant stanza:
   (external_variant
     (virtual_library vlibfoo)
-    (variant "somevariant")
+    (variant somevariant)
     (implementation impl))
   [1]

test/blackbox-tests/test-cases/variants-only-package/project-2/impl2foo/dune

@@ -0,0 +1,6 @@
+(library
+ (name impl2foo)
+ (public_name impl2foo)
+ (implements vlibfoo)
+ (variant somevariant2)
+)

test/blackbox-tests/test-cases/variants-only-package/project/dune-project

@@ -0,0 +1,2 @@
+(lang dune 1.10)
+(using library_variants 0.1)

test/blackbox-tests/test-cases/variants-only-package/project/implfoo/vlibfoo.ml

@@ -0,0 +1 @@
+let implme () = ()

test/blackbox-tests/test-cases/variants-only-package/run.t

@@ -1,9 +1,9 @@
 Check that local variant implementations are correctly exported in the list of
 known_implementations implementations when using -p
 
-  $ dune build -p vlibfoo
+  $ cd project && dune build -p vlibfoo
 
-  $ cat _build/install/default/lib/vlibfoo/dune-package
+  $ cat project/_build/install/default/lib/vlibfoo/dune-package
   (lang dune 1.11)
   (name vlibfoo)
   (library
@@ -23,3 +23,25 @@ known_implementations implementations when using -p
       (kind virtual)
       (intf)))
     (wrapped true)))
+
+Also check that the implementation correctly builds while using -p when part of the same project
+
+  $ cp -r project/_build/ opam
+
+  $ cd project && env OCAMLPATH=../opam/install/default/lib dune build -p implfoo
+
+And fail if it's not part of the same project.
+
+  $ cd project-2 && env OCAMLPATH=../opam/install/default/lib dune build -p impl2foo
+  File "impl2foo/dune", line 4, characters 13-20:
+  4 |  (implements vlibfoo)
+                   ^^^^^^^
+  Error: Virtual library "vlibfoo" doesn't know about implementation "impl2foo"
+  with variant "somevariant2". Instead of using (variant somevariant2) here,
+  you need to reference it in the virtual library project, using the
+  external_variant stanza:
+  (external_variant
+    (virtual_library vlibfoo)
+    (variant somevariant2)
+    (implementation impl2foo))
+  [1]