fix(pkg): print depexts message when a program is not found (#11005)

* fix(pkg): print depexts message when a program is not found

Signed-off-by: Alpha DIALLO <[email protected]>

src/dune_rules/pkg_rules.ml

@@ -579,6 +579,16 @@ module Substitute = struct
   let action expander ~src ~dst = A.action { Spec.expander; src; dst }
 end
 
+let depexts_hint = function
+  | [] -> None
+  | depexts ->
+    [ Pp.textf "You may want to verify the following depexts are installed:"
+    ; Pp.enumerate ~f:Pp.verbatim depexts
+    ]
+    |> Pp.concat_map ~sep:Pp.cut ~f:(fun pp -> Pp.box pp)
+    |> Option.some
+;;
+
 module Run_with_path = struct
   module Output : sig
     type error
@@ -616,30 +626,28 @@ module Run_with_path = struct
     ;;
 
     let to_paragraphs t error =
-      let pkg_name, loc = t.pkg in
-      let depexts_warning =
-        match t.depexts with
-        | [] -> []
-        | _ :: _ ->
-          [ Pp.textf "You may want to verify the following depexts are installed:"
-          ; Pp.enumerate ~f:Pp.verbatim t.depexts
-          ]
-      in
-      let pp_pkg = Pp.textf "Logs for package %s" (Package.Name.to_string pkg_name) in
-      [ pp_pkg; Pp.verbatim error ] @ depexts_warning, loc
+      let pp_pkg = Pp.textf "Logs for package %s" (Package.Name.to_string (fst t.pkg)) in
+      [ pp_pkg; Pp.verbatim error ]
     ;;
 
     let prerr ~rc error =
+      let hints =
+        lazy
+          (match depexts_hint error.depexts with
+           | None -> []
+           | Some h -> [ h ])
+      in
+      let loc = snd error.pkg in
       match Predicate.test error.accepted_exit_codes rc, error.display with
       | false, _ ->
-        let paragraphs, loc = Stdune.Io.read_file error.filename |> to_paragraphs error in
-        User_warning.emit ~loc ~is_error:true paragraphs
+        let paragraphs = Stdune.Io.read_file error.filename |> to_paragraphs error in
+        User_warning.emit ~hints:(Lazy.force hints) ~loc ~is_error:true paragraphs
       | true, Display.Verbose ->
         let content = Stdune.Io.read_file error.filename in
         if not (String.is_empty content)
         then (
-          let paragraphs, loc = to_paragraphs error content in
-          User_warning.emit ~loc paragraphs)
+          let paragraphs = to_paragraphs error content in
+          User_warning.emit ~hints:(Lazy.force hints) ~loc paragraphs)
       | true, _ -> ()
     ;;
   end
@@ -943,8 +951,13 @@ module Action_expander = struct
                 >>| (function
                  | Some p -> Ok p
                  | None ->
+                   let hint =
+                     depexts_hint t.depexts
+                     |> Option.map ~f:(fun pp -> Format.asprintf "%a" Pp.to_fmt pp)
+                   in
                    Error
                      (Action.Prog.Not_found.create
+                        ?hint
                         ~program
                         ~context:t.context
                         ~loc:(Some loc)

test/blackbox-tests/test-cases/pkg/depexts/error-message.t

@@ -37,8 +37,8 @@ Make dune.lock files with known program "dune".
   >   (checksum md5=$(md5sum foo.tar | cut -f1 -d' '))))
   > EOF
 
-Build the project, when it fails building 'foo' package, it shows
-the depexts error message.
+Build the project, when it fails building 'foo' package, it shows the depexts
+error message.
   $ dune build
   File "dune.lock/foo.pkg", line 3, characters 6-10:
   3 |  (run dune build))
@@ -47,7 +47,7 @@ the depexts error message.
   File "dune-project", line 1, characters 0-0:
   Error: Invalid first line, expected: (lang <lang> <version>)
 
-  You may want to verify the following depexts are installed:
+  Hint: You may want to verify the following depexts are installed:
   - unzip
   - gnupg
   [1]
@@ -65,13 +65,14 @@ Make dune.lock files with unknown program and unknown package.
   >   (checksum md5=$(md5sum foo.tar | cut -f1 -d' '))))
   > EOF
 
-Doing the same build which is supposed to show the depexts message at the end.
-There is a bug at the moment, it shows the correct error message but without
-depexts message.
+Running the same build. It is supposed to show the depexts message at the end,
+when the program is not found.
   $ dune build
   File "dune.lock/foo.pkg", line 3, characters 6-21:
   3 |  (run unknown-program))
             ^^^^^^^^^^^^^^^
   Error: Program unknown-program not found in the tree or in PATH
    (context: default)
+  Hint: You may want to verify the following depexts are installed:
+  - unknown-package
   [1]