show proper errors on public libs collision

Signed-off-by: Javier Chávarri <javier.chavarri@gmail.com>

src/dune_rules/gen_rules.ml

@@ -111,25 +111,32 @@ end = struct
       let+ () = Toplevel.Stanza.setup ~sctx ~dir ~toplevel in
       empty_none
     | Library.T lib ->
-      let* lib_info =
-        let* ocaml =
-          let ctx = Super_context.context sctx in
-          Context.ocaml ctx
-        in
-        let lib_config = ocaml.lib_config in
-        Memo.return (Library.to_lib_info lib ~dir ~lib_config)
-      in
-      let* enabled_in_context =
-        let* enabled = Lib_info.enabled lib_info in
-        match enabled with
-        | Disabled_because_of_enabled_if -> Memo.return false
-        | Normal | Optional -> Memo.return true
-      in
-      let* available = Lib.DB.available (Scope.libs scope) (Library.best_name lib) in
-      if_available_buildable
-        ~loc:lib.buildable.loc
-        (fun () -> Lib_rules.rules lib ~sctx ~dir ~scope ~dir_contents ~expander)
-        (enabled_in_context && available)
+      let db = Scope.libs scope in
+      (* This check reveals conflicts between the private names of public libraries,
+         otherwise the user will see duplicated rules for their cmxs *)
+      let* res = Lib.DB.find_invalid db (Library.private_name lib) in
+      (match res with
+       | Some err -> User_error.raise [ User_message.pp err ]
+       | None ->
+         let* lib_info =
+           let* ocaml =
+             let ctx = Super_context.context sctx in
+             Context.ocaml ctx
+           in
+           let lib_config = ocaml.lib_config in
+           Memo.return (Library.to_lib_info lib ~dir ~lib_config)
+         in
+         let* enabled_in_context =
+           let* enabled = Lib_info.enabled lib_info in
+           match enabled with
+           | Disabled_because_of_enabled_if -> Memo.return false
+           | Normal | Optional -> Memo.return true
+         in
+         let* available = Lib.DB.available (Scope.libs scope) (Library.best_name lib) in
+         if_available_buildable
+           ~loc:lib.buildable.loc
+           (fun () -> Lib_rules.rules lib ~sctx ~dir ~scope ~dir_contents ~expander)
+           (enabled_in_context && available))
     | Foreign.Library.T lib ->
       Expander.eval_blang expander lib.enabled_if
       >>= if_available (fun () ->

src/dune_rules/lib.ml

@@ -1941,6 +1941,14 @@ module DB = struct
     | Ignore | Not_found | Invalid _ | Hidden _ -> None
   ;;
 
+  let find_invalid t name =
+    let open Memo.O in
+    Resolve_names.find_internal t name
+    >>| function
+    | Invalid err -> Some err
+    | Found _ | Ignore | Not_found | Hidden _ -> None
+  ;;
+
   let find_even_when_hidden t name =
     let open Memo.O in
     Resolve_names.find_internal t name

src/dune_rules/lib.mli

@@ -122,6 +122,7 @@ module DB : sig
     -> t
 
   val find : t -> Lib_name.t -> lib option Memo.t
+  val find_invalid : t -> Lib_name.t -> User_message.t option Memo.t
   val find_even_when_hidden : t -> Lib_name.t -> lib option Memo.t
   val available : t -> Lib_name.t -> bool Memo.t
 

src/dune_rules/stanzas/library.ml

@@ -366,6 +366,7 @@ let best_name t =
   | Public p -> snd p.name
 ;;
 
+let private_name t = Lib_name.of_local t.name
 let is_virtual t = Option.is_some t.virtual_modules
 let is_impl t = Option.is_some t.implements
 

src/dune_rules/stanzas/library.mli

@@ -72,6 +72,7 @@ val foreign_lib_files
 val archive : t -> dir:Path.Build.t -> ext:string -> Path.Build.t
 
 val best_name : t -> Lib_name.t
+val private_name : t -> Lib_name.t
 val is_virtual : t -> bool
 val is_impl : t -> bool
 val obj_dir : dir:Path.Build.t -> t -> Path.Build.t Obj_dir.t

test/blackbox-tests/test-cases/lib-collision/lib-collision-private-same-folder.t

@@ -15,6 +15,13 @@ the same folder.
 Without any consumers of the libraries
 
   $ dune build
+  Error:
+  File "dune", line 1, characters 0-21:
+  Error: A library with name "foo" is defined in two folders: _build/default
+  and _build/default. Either change one of the names, or enable them
+  conditionally using the 'enabled_if' field.
+
+  [1]
 
 With some consumer of the library
 
@@ -33,6 +40,12 @@ With some consumer of the library
   > EOF
 
   $ dune build
+  Error:
+  File "dune", line 1, characters 0-21:
+  Error: A library with name "foo" is defined in two folders: _build/default
+  and _build/default. Either change one of the names, or enable them
+  conditionally using the 'enabled_if' field.
+
   File "dune", line 3, characters 0-21:
   3 | (library
   4 |  (name foo))

test/blackbox-tests/test-cases/lib-collision/lib-collision-private.t

@@ -20,6 +20,14 @@ different folders.
 Without any consumers of the libraries
 
   $ dune build
+  Error:
+  File "b/dune", line 1, characters 0-21:
+  Error: A library with name "foo" is defined in two folders: _build/default/a
+  and _build/default/b. Either change one of the names, or enable them
+  conditionally using the 'enabled_if' field.
+
+  -> required by alias default
+  [1]
 
 With some consumer of the library
 
@@ -34,6 +42,13 @@ With some consumer of the library
   > EOF
 
   $ dune build
+  Error:
+  File "b/dune", line 1, characters 0-21:
+  Error: A library with name "foo" is defined in two folders: _build/default/a
+  and _build/default/b. Either change one of the names, or enable them
+  conditionally using the 'enabled_if' field.
+
+  -> required by alias default
   File "b/dune", line 1, characters 0-21:
   1 | (library
   2 |  (name foo))

test/blackbox-tests/test-cases/lib-collision/lib-collision-public-same-folder.t

@@ -19,9 +19,12 @@ the same folder.
 Without any consumers of the libraries
 
   $ dune build
-  Error: Multiple rules generated for _build/default/foo.cmxs:
-  - dune:4
-  - dune:1
+  Error:
+  File "dune", line 1, characters 0-44:
+  Error: A library with name "foo" is defined in two folders: _build/default
+  and _build/default. Either change one of the names, or enable them
+  conditionally using the 'enabled_if' field.
+
   [1]
 
 With some consumer
@@ -43,6 +46,12 @@ With some consumer
   > EOF
 
   $ dune build
+  Error:
+  File "dune", line 1, characters 0-44:
+  Error: A library with name "foo" is defined in two folders: _build/default
+  and _build/default. Either change one of the names, or enable them
+  conditionally using the 'enabled_if' field.
+
   File "dune", line 1, characters 0-0:
   Error: Module "Main" is used in several stanzas:
   - dune:1

test/blackbox-tests/test-cases/lib-collision/lib-collision-public.t

@@ -24,6 +24,17 @@ different folders.
 Without any consumers of the libraries
 
   $ dune build
+  Error:
+  File "b/dune", line 1, characters 0-44:
+  Error: A library with name "foo" is defined in two folders: _build/default/a
+  and _build/default/b. Either change one of the names, or enable them
+  conditionally using the 'enabled_if' field.
+
+  -> required by _build/install/default/lib/bar/foo/foo.a
+  -> required by _build/default/bar.install
+  -> required by alias all
+  -> required by alias default
+  [1]
 
 With some consumer
 
@@ -38,6 +49,16 @@ With some consumer
   > EOF
 
   $ dune build
+  Error:
+  File "b/dune", line 1, characters 0-44:
+  Error: A library with name "foo" is defined in two folders: _build/default/a
+  and _build/default/b. Either change one of the names, or enable them
+  conditionally using the 'enabled_if' field.
+
+  -> required by _build/install/default/lib/bar/foo/foo.a
+  -> required by _build/default/bar.install
+  -> required by alias all
+  -> required by alias default
   File "b/dune", line 1, characters 0-44:
   1 | (library
   2 |  (name foo)