Libraries and executables can allow overlapping dependencies

doc/jbuild.rst

@@ -177,6 +177,9 @@ modules you want.
   such modules to avoid surprises. ``<modules>`` must be a subset of
   the modules listed in the ``(modules ...)`` field.
 
+- ``(allow_overlapping_dependencies)`` allows external dependencies to
+  overlap with libraries that are present in the workspace
+
 Note that when binding C libraries, Jbuilder doesn't provide special support for
 tools such as ``pkg-config``, however it integrates easily with `configurator
 <https://github.com/janestreet/configurator>`__ by using ``(c_flags (:include
@@ -263,6 +266,9 @@ binary at the same place as where ``ocamlc`` was found, or when there is a
 - ``(modules_without_implementation <modules>)`` is the same as the
   corresponding field of `library`_
 
+- ``(allow_overlapping_dependencies)`` is the same as the
+  corresponding field of `library`_
+
 executables
 -----------
 

src/gen_rules.ml

@@ -559,7 +559,10 @@ module Gen(P : Install_rules.Params) = struct
             |> String.concat ~sep:"\n")
          >>> Build.write_file_dyn (Path.relative dir file.name)));
 
-    let compile_info = Lib.DB.get_compile_info (Scope.libs scope) lib.name in
+    let compile_info =
+      Lib.DB.get_compile_info (Scope.libs scope) lib.name
+        ~allow_overlaps:lib.buildable.allow_overlapping_dependencies
+    in
     let requires, real_requires =
       SC.Libs.requires sctx compile_info
         ~dir ~has_dot_merlin:true
@@ -810,6 +813,7 @@ module Gen(P : Install_rules.Params) = struct
       Lib.DB.resolve_user_written_deps (Scope.libs scope)
         exes.buildable.libraries
         ~pps:(Jbuild.Preprocess_map.pps exes.buildable.preprocess)
+        ~allow_overlaps:exes.buildable.allow_overlapping_dependencies
     in
     let requires, real_requires =
       SC.Libs.requires sctx ~dir

src/jbuild.ml

@@ -476,6 +476,7 @@ module Buildable = struct
     ; ocamlc_flags             : Ordered_set_lang.Unexpanded.t
     ; ocamlopt_flags           : Ordered_set_lang.Unexpanded.t
     ; js_of_ocaml              : Js_of_ocaml.t
+    ; allow_overlapping_dependencies : bool
     }
 
   let modules_field name =
@@ -487,8 +488,6 @@ module Buildable = struct
     >>= fun preprocess ->
     field "preprocessor_deps" (list Dep_conf.t) ~default:[]
     >>= fun preprocessor_deps ->
-    (* CR-someday jdimino: remove this. There are still a few Jane Street packages using
-       this *)
     field "lint" Lint.t ~default:Lint.default
     >>= fun lint ->
     modules_field "modules"
@@ -500,7 +499,10 @@ module Buildable = struct
     field_oslu "flags"          >>= fun flags          ->
     field_oslu "ocamlc_flags"   >>= fun ocamlc_flags   ->
     field_oslu "ocamlopt_flags" >>= fun ocamlopt_flags ->
-    field "js_of_ocaml" (Js_of_ocaml.t) ~default:Js_of_ocaml.default >>= fun js_of_ocaml ->
+    field "js_of_ocaml" (Js_of_ocaml.t) ~default:Js_of_ocaml.default
+    >>= fun js_of_ocaml ->
+    field_b "allow_overlapping_dependencies"
+    >>= fun allow_overlapping_dependencies ->
     return
       { loc
       ; preprocess
@@ -513,6 +515,7 @@ module Buildable = struct
       ; ocamlc_flags
       ; ocamlopt_flags
       ; js_of_ocaml
+      ; allow_overlapping_dependencies
       }
 
   let single_preprocess t =
@@ -867,7 +870,8 @@ module Rule = struct
             return (fallback, mode))
            ~f:(function
              | true, Some _ ->
-               Error "Cannot use both (fallback) and (mode ...) at the same time.\n\
+               Error "Cannot use both (fallback) and (mode ...) at the \
+                      same time.\n\
                       (fallback) is the same as (mode fallback), \
                       please use the latter in new code."
              | false, Some mode -> Ok mode

src/jbuild.mli

@@ -143,6 +143,7 @@ module Buildable : sig
     ; ocamlc_flags             : Ordered_set_lang.Unexpanded.t
     ; ocamlopt_flags           : Ordered_set_lang.Unexpanded.t
     ; js_of_ocaml              : Js_of_ocaml.t
+    ; allow_overlapping_dependencies : bool
     }
 
   (** Preprocessing specification used by all modules or [No_preprocessing] *)