feat: allow multiple (dirs ..) stanzas

doc/changes/added/13734.md

@@ -0,0 +1,4 @@
+- Allow multiple `(dirs ..)` stanzas in the same Dune file. Starting with
+  `(lang dune 3.23)`, Dune takes the union of the specified directories
+  (#13734, fixes #6249, @anmonteiro)
+

src/source/dune_file.ml

@@ -288,7 +288,7 @@ module Ast = struct
     fields
     @@
     let+ subdirs = multi_field "subdir" (subdir ~inside_include)
-    and+ dirs = field_o "dirs" dirs
+    and+ dirs = multi_field "dirs" dirs
     and+ files = field_o "files" files
     and+ ignored_sub_dirs =
       multi_field "ignored_subdirs" (ignored_sub_dirs ~inside_subdir)
@@ -298,7 +298,7 @@ module Ast = struct
     and+ rest = leftover_fields in
     let ast =
       List.concat
-        [ Option.to_list dirs
+        [ dirs
         ; Option.to_list files
         ; Option.to_list vendored_dirs
         ; subdirs
@@ -410,7 +410,7 @@ module Group = struct
     { Source_dir_status.Map.normal = dirs; data_only; vendored = vendored_dirs }
   ;;
 
-  let combine t (ast : Ast.t) =
+  let combine ~dune_version t (ast : Ast.t) =
     match ast with
     | Ignored_sub_dirs (loc, glob) ->
       { t with ignored_sub_dirs = (loc, glob) :: t.ignored_sub_dirs }
@@ -420,15 +420,25 @@ module Group = struct
       }
     | Vendored_dirs (loc, glob) ->
       { t with vendored_dirs = Some (no_dupes "vendored_dirs" loc t.vendored_dirs glob) }
-    | Dirs (loc, glob) -> { t with dirs = Some (no_dupes "dirs" loc t.dirs glob) }
+    | Dirs (loc, glob) ->
+      let dirs =
+        if dune_version >= (3, 23)
+        then (
+          match t.dirs with
+          | None -> loc, glob
+          | Some (existing_loc, existing_glob) ->
+            existing_loc, Predicate_lang.or_ [ existing_glob; glob ])
+        else no_dupes "dirs" loc t.dirs glob
+      in
+      { t with dirs = Some dirs }
     | Files (loc, glob) -> { t with files = Some (no_dupes "files" loc t.files glob) }
     | Subdir (path, stanzas) -> { t with subdirs = (path, stanzas) :: t.subdirs }
     | Leftovers stanzas -> { t with leftovers = List.rev_append stanzas t.leftovers }
     | Include _ -> assert false
   ;;
 
-  let of_ast (ast : Ast.t list) =
-    let t = List.fold_left ast ~init:empty ~f:combine in
+  let of_ast (ast : Ast.t list) ~dune_version =
+    let t = List.fold_left ast ~init:empty ~f:(combine ~dune_version) in
     let t = { t with leftovers = List.rev t.leftovers } in
     match t.data_only_dirs, t.dirs, t.ignored_sub_dirs with
     | _, Some (loc, _), _ :: _ ->
@@ -445,16 +455,16 @@ module Group = struct
   ;;
 end
 
-let rec to_dir_map ast =
-  let group = Group.of_ast ast in
+let rec to_dir_map ast ~dune_version =
+  let group = Group.of_ast ast ~dune_version in
   let node =
     let subdir_status = Group.subdir_status group in
     let files = group.files in
     Dir_map.singleton { Dir_map.Per_dir.sexps = group.leftovers; subdir_status; files }
   in
   let subdirs =
     List.map group.subdirs ~f:(fun (path, stanzas) ->
-      Dir_map.make_at_path (Path.Local.explode path) (to_dir_map stanzas))
+      Dir_map.make_at_path (Path.Local.explode path) (to_dir_map stanzas ~dune_version))
   in
   Dir_map.merge_all (node :: subdirs)
 ;;
@@ -478,7 +488,7 @@ let decode ~file project sexps =
        ~inside_subdir
        ~inside_include
        Filename.current_dir_name
-  >>| to_dir_map
+  >>| to_dir_map ~dune_version:(Dune_project.dune_version project)
 ;;
 
 type t =

test/blackbox-tests/lacking-description

@@ -113,7 +113,6 @@
 ./test-cases/stanzas/env/env-link_flags.t/run.t
 ./test-cases/stanzas/env/env-var-expansion/missing-default-in-blang.t/run.t
 ./test-cases/stanzas/env/env-var-expansion/nesting.t/run.t
-./test-cases/stanzas/include-stanza/github2711.t
 ./test-cases/stanzas/include-stanza/include-loop.t/run.t
 ./test-cases/stanzas/install/github2123.t/run.t
 ./test-cases/stanzas/ocamllex/ocamllex-include-qualified.t

test/blackbox-tests/test-cases/stanzas/include-stanza/github2711.t

@@ -1,3 +1,5 @@
+Dirs stanzas from included files are evaluated.
+
   $ make_dune_project 2.7
   $ cat >dune.inc <<EOF
   > (dirs foo)
@@ -9,3 +11,108 @@
   $ dune build ./foo
   $ cat _build/default/foo
   bar
+
+Multiple dirs stanzas are unioned across dune and include files.
+
+  $ mkdir composed
+  $ cd composed
+  $ make_dune_project 3.23
+  $ mkdir keep foo bar
+  $ cat >keep/dune <<EOF
+  > (rule (with-stdout-to ok (echo keep)))
+  > EOF
+  $ cat >foo/dune <<EOF
+  > (rule (with-stdout-to nope (echo foo)))
+  > EOF
+  $ cat >bar/dune <<EOF
+  > (rule (with-stdout-to nope (echo bar)))
+  > EOF
+  $ cat >dune.inc <<EOF
+  > (dirs :standard \ foo)
+  > EOF
+  $ cat >dune <<EOF
+  > (dirs :standard \ bar)
+  > (include dune.inc)
+  > EOF
+  $ dune build ./keep/ok
+  $ cat _build/default/keep/ok
+  keep
+  $ dune build ./foo/nope
+  $ cat _build/default/foo/nope
+  foo
+  $ dune build ./bar/nope
+  $ cat _build/default/bar/nope
+  bar
+  $ cd ..
+
+Dirs stanzas that use :standard are interpreted independently.
+
+  $ mkdir override
+  $ cd override
+  $ make_dune_project 3.23
+  $ mkdir keep other
+  $ cat >keep/dune <<EOF
+  > (rule (with-stdout-to ok (echo keep)))
+  > EOF
+  $ cat >other/dune <<EOF
+  > (rule (with-stdout-to nope (echo other)))
+  > EOF
+  $ cat >dune.inc <<EOF
+  > (dirs keep)
+  > EOF
+  $ cat >dune <<EOF
+  > (dirs :standard \ keep)
+  > (include dune.inc)
+  > EOF
+  $ dune build ./keep/ok
+  $ cat _build/default/keep/ok
+  keep
+  $ dune build ./other/nope
+  $ cat _build/default/other/nope
+  other
+  $ cd ..
+
+The review example evaluates to the union of all matching directories.
+
+  $ mkdir review-example
+  $ cd review-example
+  $ make_dune_project 3.23
+  $ mkdir foo keep
+  $ cat >foo/dune <<EOF
+  > (rule (with-stdout-to ok (echo foo)))
+  > EOF
+  $ cat >keep/dune <<EOF
+  > (rule (with-stdout-to ok (echo keep)))
+  > EOF
+  $ cat >dune <<EOF
+  > (dirs foo)
+  > (dirs :standard \ foo)
+  > (dirs foo)
+  > EOF
+  $ dune build ./foo/ok
+  $ cat _build/default/foo/ok
+  foo
+  $ dune build ./keep/ok
+  $ cat _build/default/keep/ok
+  keep
+  $ cd ..
+
+Before version 3.23, multiple dirs stanzas are rejected.
+
+  $ mkdir pre-3-23
+  $ cd pre-3-23
+  $ make_dune_project 3.22
+  $ cat >dune.inc <<EOF
+  > (dirs foo)
+  > EOF
+  $ cat >dune <<EOF
+  > (dirs bar)
+  > (include dune.inc)
+  > EOF
+  $ dune build
+  File "dune.inc", line 1, characters 6-9:
+  1 | (dirs foo)
+            ^^^
+  Error: may not set the "dirs" stanza more than once
+  [1]
+  $ cd ..