test: special files in directory targets (#13180)

Author: Alizter

src/dune_targets/dune_targets.ml

@@ -203,7 +203,6 @@ module Produced = struct
         ; Pp.verbatim (Unix.error_message unix_error)
         ]
       | Unsupported_file (file, kind) ->
-        (* CR-soon amokhov: This case is untested. *)
         [ Pp.textf
             "Rule produced file %S with unrecognised kind %S"
             (Path.Build.drop_build_context_maybe_sandboxed_exn file

test/blackbox-tests/test-cases/directory-targets/special-files.t

@@ -0,0 +1,53 @@
+Test that dune produces a clear error when a rule creates special files
+in its output.
+
+FIFO:
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.22)
+  > (using directory-targets 0.1)
+  > EOF
+
+  $ cat > dune <<EOF
+  > (rule
+  >   (targets (dir output))
+  >   (action
+  >    (progn
+  >     (run mkdir -p output)
+  >     (run mkfifo output/myfifo))))
+  > EOF
+
+  $ dune build output
+  File "dune", lines 1-6, characters 0-110:
+  1 | (rule
+  2 |   (targets (dir output))
+  3 |   (action
+  4 |    (progn
+  5 |     (run mkdir -p output)
+  6 |     (run mkfifo output/myfifo))))
+  Error: Rule produced file "output/myfifo" with unrecognised kind "S_FIFO"
+  [1]
+
+  $ rm -rf _build
+
+Socket:
+
+  $ cat > dune <<EOF
+  > (rule
+  >   (targets (dir output))
+  >   (action
+  >    (progn
+  >     (run mkdir -p output)
+  >     (run dune_cmd mksocket output/mysocket))))
+  > EOF
+
+  $ dune build output
+  File "dune", lines 1-6, characters 0-123:
+  1 | (rule
+  2 |   (targets (dir output))
+  3 |   (action
+  4 |    (progn
+  5 |     (run mkdir -p output)
+  6 |     (run dune_cmd mksocket output/mysocket))))
+  Error: Rule produced file "output/mysocket" with unrecognised kind "S_SOCK"
+  [1]

test/blackbox-tests/utils/dune_cmd.ml

@@ -334,6 +334,23 @@ module Wait_for_file_to_appear = struct
   let () = register name of_args run
 end
 
+module Mksocket = struct
+  let name = "mksocket"
+
+  let of_args = function
+    | [ path ] -> path
+    | _ -> raise (Arg.Bad "Usage: dune_cmd mksocket <path>")
+  ;;
+
+  let run path =
+    let sock = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0 in
+    Unix.bind sock (Unix.ADDR_UNIX path);
+    Unix.close sock
+  ;;
+
+  let () = register name of_args run
+end
+
 (* implements `exec -a` in a portable way *)
 module Exec_a = struct
   type t =