allow to use a private name when declaring external variants

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

src/lib.ml

@@ -1335,12 +1335,20 @@ module DB = struct
         Errors.fail_opt loc
           "Library %a isn't a virtual library."
           Lib_name.pp vlib
-      | Some (Redirect (None, best_name)) ->
-        Errors.fail_opt loc
-          "To declare variants you must use %a's public name,@ which is %a."
-          Lib_name.pp vlib Lib_name.pp best_name
       | _ -> ())
 
+  let error_two_impl_for_variant name (variant, (loc1, impl1), (loc2, impl2)) =
+    Errors.fail_opt None
+      "Error: Two implementations of %a have the same variant %a:\n\
+        - %a (%a)\n\
+        - %a (%a)\n"
+      Lib_name.pp name
+      Variant.pp variant
+      Lib_name.pp impl1
+      Loc.pp_file_colon_line loc1
+      Lib_name.pp impl2
+      Loc.pp_file_colon_line loc2
+
   let create_from_library_stanzas ?parent ~lib_config lib_stanzas
         variants_stanzas =
     (* Lookup the local scope to find implementations*)
@@ -1365,25 +1373,39 @@ module DB = struct
       |> Lib_name.Map.map ~f:Variant.Map.of_list
       |> Lib_name.Map.mapi ~f:(fun name -> function
         | Ok x -> x
-        | Error (variant, (loc1, impl1), (loc2, impl2)) ->
-          Errors.fail_opt None
-            "Error: Two implementations of %a have the same variant %a:\n\
-             - %a (%a)\n\
-             - %a (%a)\n"
-            Lib_name.pp name
-            Variant.pp variant
-            Lib_name.pp impl1
-            Loc.pp_file_colon_line loc1
-            Lib_name.pp impl2
-            Loc.pp_file_colon_line loc2)
+        | Error x -> error_two_impl_for_variant name x
+      )
     in
     let map =
       List.concat_map lib_stanzas ~f:(fun (dir, (conf : Dune_file.Library.t)) ->
-        let variants =
+        let variants_public =
           Dune_file.Library.best_name conf
           |> Lib_name.Map.find variant_map
           |> Option.value ~default:Variant.Map.empty
         in
+        let variants_private =
+          conf.public
+          |> Option.map
+          ~f:(fun p ->
+            let name = Dune_file.Public_lib.name p in
+            if (Lib_name.equal name (Lib_name.of_local conf.name)) then
+              Variant.Map.empty
+            else
+              (Lib_name.of_local conf.name)
+              |> Lib_name.Map.find variant_map
+              |> Option.value ~default:Variant.Map.empty
+            )
+          |> Option.value ~default:Variant.Map.empty
+        in
+        let variants = Variant.Map.merge variants_private variants_public
+          ~f:(fun variant a b -> match a, b with
+            | Some a, Some b ->
+                error_two_impl_for_variant
+                  (Dune_file.Library.best_name conf)
+                  (variant, a, b)
+            | Some a, _ -> Some a
+            | _, b -> b)
+        in
         let info = Lib_info.of_library_stanza ~dir ~lib_config variants conf in
         match conf.public with
         | None ->

test/blackbox-tests/test-cases/variants-external-declaration-conflict/not-a-vlib-redirect/dune → test/blackbox-tests/test-cases/variants-external-declaration-conflict/public-private/dune

@@ -6,3 +6,8 @@
  (virtual_library libfoo)
  (variant somevariant)
  (implementation impl1))
+
+(external_variant
+ (virtual_library another-name)
+ (variant somevariant)
+ (implementation impl2))

test/blackbox-tests/test-cases/variants-external-declaration-conflict/run.t

@@ -34,15 +34,11 @@ implementation with the same variant.
   Error: Library libfoo isn't a virtual library.
   [1]
 
-  $ dune build --root not-a-vlib-redirect
-  Entering directory 'not-a-vlib-redirect'
-  File "dune", line 5, characters 0-91:
-  5 | (external_variant
-  6 |  (virtual_library libfoo)
-  7 |  (variant somevariant)
-  8 |  (implementation impl1))
-  Error: To declare variants you must use libfoo's public name,
-  which is another-name.
+  $ dune build --root public-private
+  Entering directory 'public-private'
+  Error: Two implementations of another-name have the same variant "somevariant":
+  - impl1 (dune:5)
+  - impl2 (dune:10)
   [1]
 
   $ dune build --root vlib-dont-exist

test/blackbox-tests/test-cases/variants-external-declaration/exe/dune

@@ -1,4 +1,4 @@
 (executable
  (name exe)
- (libraries vlibfoo)
+ (libraries vlibfoo-ext)
  (variants somevariant))

test/blackbox-tests/test-cases/variants-external-declaration/prj1/dune

@@ -1,10 +1,16 @@
 (library
  (name vlibfoo)
- (public_name vlibfoo)
+ (public_name vlibfoo-ext)
  (virtual_modules vlibfoo)
 )
 
 (external_variant
   (virtual_library vlibfoo)
   (variant somevariant)
-  (implementation impl))
+  (implementation impl))
+
+
+(external_variant
+  (virtual_library vlibfoo-ext)
+  (variant somevariant-2)
+  (implementation impl-2))

test/blackbox-tests/test-cases/variants-external-declaration/prj2/dune

@@ -1,4 +1,4 @@
 (library
  (name impl)
  (public_name impl)
- (implements vlibfoo))
+ (implements vlibfoo-ext))

test/blackbox-tests/test-cases/variants-external-declaration/run.t

@@ -3,17 +3,17 @@ declared in the virtual library definition.
 
   $ dune build exe/exe.exe
 
-  $ dune build -p vlibfoo
+  $ dune build -p vlibfoo-ext
 
-  $ cat _build/install/default/lib/vlibfoo/dune-package
+  $ cat _build/install/default/lib/vlibfoo-ext/dune-package
   (lang dune 1.10)
-  (name vlibfoo)
+  (name vlibfoo-ext)
   (library
-   (name vlibfoo)
+   (name vlibfoo-ext)
    (kind normal)
    (virtual)
    (foreign_archives (native vlibfoo$ext_lib))
-   (known_implementations (somevariant impl))
+   (known_implementations (somevariant impl) (somevariant-2 impl-2))
    (main_module_name Vlibfoo)
    (modes byte native)
    (modules