Warn when dune-project does not exist

CHANGES.md

@@ -130,6 +130,8 @@ Unreleased
 - Dune no longer automatically create or edit `dune-project` files
   (#4239, fixes #4108, @jeremiedimino)
 
+- Warn if `dune-project` is not found (fatal in release mode) (#5343, @emillon)
+
 - Cleanup temporary files after running `$ dune exec`. (#4260, fixes #4243,
   @rgrinberg)
 

bin/common.ml

@@ -51,6 +51,7 @@ type t =
   ; workspace_config : Dune_rules.Workspace.Clflags.t
   ; cache_debug_flags : Dune_engine.Cache_debug_flags.t
   ; report_errors_config : Dune_engine.Report_errors_config.t
+  ; require_dune_project_file : bool
   }
 
 let capture_outputs t = t.capture_outputs
@@ -204,6 +205,11 @@ let init ?log_file c =
   Clflags.promote_install_files := c.promote_install_files;
   Clflags.always_show_command_line := c.always_show_command_line;
   Clflags.ignore_promoted_rules := c.ignore_promoted_rules;
+  Clflags.on_missing_dune_project_file :=
+    if c.require_dune_project_file then
+      Error
+    else
+      Warn;
   Dune_util.Log.info
     [ Pp.textf "Workspace root: %s"
         (Path.to_absolute_filename Path.root |> String.maybe_quoted)
@@ -313,6 +319,7 @@ module Options_implied_by_dash_p = struct
     ; default_target : Arg.Dep.t
     ; always_show_command_line : bool
     ; promote_install_files : bool
+    ; require_dune_project_file : bool
     }
 
   let docs = copts_sect
@@ -413,6 +420,12 @@ module Options_implied_by_dash_p = struct
         last
         & opt_all ~vopt:true bool [ false ]
         & info [ "promote-install-files" ] ~docs ~doc)
+    and+ require_dune_project_file =
+      let doc = "Fail if a dune-project file is missing." in
+      Arg.(
+        last
+        & opt_all ~vopt:true bool [ false ]
+        & info [ "require-dune-project-file" ] ~docs ~doc)
     in
     { root
     ; only_packages = No_restriction
@@ -422,6 +435,7 @@ module Options_implied_by_dash_p = struct
     ; default_target
     ; always_show_command_line
     ; promote_install_files
+    ; require_dune_project_file
     }
 
   let dash_dash_release =
@@ -436,6 +450,7 @@ module Options_implied_by_dash_p = struct
           ; "release"
           ; "--always-show-command-line"
           ; "--promote-install-files"
+          ; "--require-dune-project-file"
           ; "--default-target"
           ; "@install"
           ]
@@ -444,10 +459,11 @@ module Options_implied_by_dash_p = struct
             "Put $(b,dune) into a reproducible $(i,release) mode. This is in \
              fact a shorthand for $(b,--root . --ignore-promoted-rules \
              --no-config --profile release --always-show-command-line \
-             --promote-install-files --default-target @install). You should \
-             use this option for release builds. For instance, you must use \
-             this option in your $(i,<package>.opam) files. Except if you \
-             already use $(b,-p), as $(b,-p) implies this option.")
+             --promote-install-files --default-target @install \
+             --require-dune-project-file). You should use this option for \
+             release builds. For instance, you must use this option in your \
+             $(i,<package>.opam) files. Except if you already use $(b,-p), as \
+             $(b,-p) implies this option.")
 
   let options =
     let+ t = options
@@ -872,6 +888,7 @@ let term ~default_root_is_cwd =
        ; default_target
        ; always_show_command_line
        ; promote_install_files
+       ; require_dune_project_file
        } =
     Options_implied_by_dash_p.term
   and+ x =
@@ -1042,6 +1059,7 @@ let term ~default_root_is_cwd =
       }
   ; cache_debug_flags
   ; report_errors_config
+  ; require_dune_project_file
   }
 
 let set_rpc t rpc = { t with rpc = Some rpc }

bin/init.ml

@@ -210,6 +210,7 @@ let term =
       & info [ "pkg" ] ~docv ~doc)
   in
   let _config = Common.init common_term in
+  Dune_engine.Clflags.on_missing_dune_project_file := Dune_engine.Clflags.Ignore;
   let open Component in
   let context = Init_context.make path in
   let common : Options.Common.t = { name; libraries; pps } in

src/dune_engine/clflags.ml

@@ -37,3 +37,10 @@ let always_show_command_line = ref false
 let promote_install_files = ref false
 
 let ignore_promoted_rules = ref false
+
+type on_missing_dune_project_file =
+  | Error
+  | Warn
+  | Ignore
+
+let on_missing_dune_project_file = ref Warn

src/dune_engine/clflags.mli

@@ -53,3 +53,11 @@ val promote_install_files : bool ref
 
 (** Whether we are ignoring rules with [(mode promote)] *)
 val ignore_promoted_rules : bool ref
+
+type on_missing_dune_project_file =
+  | Error
+  | Warn
+  | Ignore
+
+(** Desired behavior when dune project file is absent *)
+val on_missing_dune_project_file : on_missing_dune_project_file ref

src/dune_engine/dune_project.ml

@@ -267,10 +267,6 @@ let default_dune_language_version =
 let get_dune_lang () =
   { (Lang.get_exn "dune") with version = !default_dune_language_version }
 
-type created_or_already_exist =
-  | Created
-  | Already_exist
-
 module Extension = struct
   type 'a t = 'a Univ_map.Key.t
 

src/dune_engine/dune_project.mli

@@ -152,10 +152,6 @@ val anonymous :
 (** "dune-project" *)
 val filename : string
 
-type created_or_already_exist =
-  | Created
-  | Already_exist
-
 (** Default language version to use for projects that don't have a
     [dune-project] file. The default value is the latest version of the dune
     language. *)

src/dune_engine/source_tree.ml

@@ -476,6 +476,44 @@ end = struct
       (visited, init)
   end
 
+  let ensure_dune_project_file_exists =
+    let memo =
+      let module Input = struct
+        type t = [ `Is_error of bool ] * Dune_project.t
+
+        let equal (a1, p1) (a2, p2) =
+          Poly.equal a1 a2 && Dune_project.equal p1 p2
+
+        let hash = Tuple.T2.hash Poly.hash Dune_project.hash
+
+        let to_dyn (`Is_error b, project) =
+          Dyn.(pair bool Dune_project.to_dyn) (b, project)
+      end in
+      Memo.create "ensure-dune-project-file-exists"
+        ~input:(module Input)
+        (fun (`Is_error is_error, project) ->
+          let open Memo.Build.O in
+          let+ exists =
+            Dune_project.file project |> Path.source |> Fs_memo.file_exists
+          in
+          if not exists then
+            User_warning.emit ~is_error
+              ~hints:
+                [ Pp.text
+                    "generate the project file with: $ dune init project <name>"
+                ]
+              [ Pp.text
+                  "No dune-project file has been found. A default one is \
+                   assumed but the project might break when dune is upgraded. \
+                   Please create a dune-project file."
+              ])
+    in
+    fun inp ->
+      match !Clflags.on_missing_dune_project_file with
+      | Ignore -> Memo.Build.return ()
+      | Warn -> Memo.exec memo (`Is_error false, inp)
+      | Error -> Memo.exec memo (`Is_error true, inp)
+
   let dune_file ~(dir_status : Sub_dirs.Status.t) ~path ~files ~project =
     let file_exists =
       if dir_status = Data_only then
@@ -511,6 +549,8 @@ end = struct
       | None, Some (path, _) -> Some path
     in
     Memo.Build.Option.map file ~f:(fun file ->
+        let open Memo.Build.O in
+        let* () = ensure_dune_project_file_exists project in
         let file_exists = Option.is_some file_exists in
         let from_parent = Option.map from_parent ~f:snd in
         Dune_file.load file ~file_exists ~project ~from_parent)

test/blackbox-tests/test-cases/coq/github3624.t/run.t

@@ -8,6 +8,10 @@ that the error message is good when the coq extension is not enabled.
   >  (name foo))
   > EOF
   $ dune build
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
   File "dune", line 1, characters 0-24:
   1 | (coq.theory
   2 |  (name foo))

test/blackbox-tests/test-cases/dune-init.t/run.t

@@ -20,6 +20,10 @@ Can init a public library
 Can build the public library
 
   $ (cd _test_lib_dir && touch test_lib.opam && dune build)
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
   $ cat ./_test_lib_dir/dune
   (library
    (public_name test_lib)
@@ -68,10 +72,18 @@ Can init a public executable
 Can build an executable
 
   $ (cd _test_bin_dir && touch test_bin.opam && dune build)
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
 
 Can run the created executable
 
   $ (cd _test_bin_dir && dune exec test_bin)
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
   Hello, World!
 
 Clean up the executable tests
@@ -145,10 +157,18 @@ Can init a library and dependent executable in a combo project
 Can build the combo project
 
   $ (cd _test_lib_exe_dir && touch test_bin.opam && dune build)
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
 
 Can run the combo project
 
   $ (cd _test_lib_exe_dir && dune exec test_bin)
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
   Hello, World!
 
 Clean up the combo project
@@ -175,6 +195,10 @@ Can add multiple libraries in the same directory
 Can build the multiple library project
 
   $ (cd _test_lib && touch test_lib1.opam && dune build)
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
 
 Clan up the multiple library project
 

test/blackbox-tests/test-cases/github1529.t/run.t

@@ -2,6 +2,10 @@ Reproduction case for #1529: using an extension when no dune-project
 file is present.
 
   $ dune build @install 2>&1 | sed "s/(lang dune .*)/(lang dune <version>)/" | sed "s/(using menhir .*)/(using menhir <version>)/"
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
   File "dune", line 1, characters 0-25:
   1 | (menhir (modules parser))
       ^^^^^^^^^^^^^^^^^^^^^^^^^

test/blackbox-tests/test-cases/github4682.t/dune-project

@@ -0,0 +1 @@
+(lang dune 2.8)

test/blackbox-tests/test-cases/github4684.t

@@ -3,6 +3,9 @@ build failure:
 
   $ echo "module X = Root.Unix" > main.ml
   $ touch main.opam
+  $ cat >dune-project <<EOF
+  > (lang dune 2.8)
+  > EOF
   $ cat >dune <<EOF
   > (library
   >  (name main)

test/blackbox-tests/test-cases/github4936.t

@@ -1,6 +1,9 @@
 C stubs and the tests stanza
 
   $ touch e.ml stubs.c
+  $ cat > dune-project << EOF
+  > (lang dune 2.0)
+  > EOF
   $ cat > dune << EOF
   > (test
   >  (name e)

test/blackbox-tests/test-cases/no-dune-project.t

@@ -0,0 +1,44 @@
+When no dune-project file is present, a warning is printed.
+
+  $ touch dune
+  $ dune build
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
+
+In release mode, this is fatal.
+
+  $ dune build --release
+  Error: No dune-project file has been found. A default one is assumed but the
+  project might break when dune is upgraded. Please create a dune-project file.
+  Hint: generate the project file with: $ dune init project <name>
+  [1]
+
+This corresponds to a flag:
+
+  $ dune build --require-dune-project-file
+  Error: No dune-project file has been found. A default one is assumed but the
+  project might break when dune is upgraded. Please create a dune-project file.
+  Hint: generate the project file with: $ dune init project <name>
+  [1]
+
+Test case: warning should be emitted
+
+  $ mkdir nested-case && cd nested-case
+  $ mkdir a && touch a/dune
+  $ dune build
+  Warning: No dune-project file has been found. A default one is assumed but
+  the project might break when dune is upgraded. Please create a dune-project
+  file.
+  Hint: generate the project file with: $ dune init project <name>
+  $ cd ..
+
+Test case: warning should not be emitted
+
+  $ mkdir another-case && cd another-case
+  $ mkdir a && touch a/dune
+  $ echo "(lang dune 3.0)" > a/dune-project
+  $ cp -R a b
+  $ dune build
+  $ cd ..

test/blackbox-tests/test-cases/promote/dep-on-promoted-target.t/run.t

@@ -1,5 +1,9 @@
 Depending on a promoted file works.
 
+  $ cat > dune-project <<EOF
+  > (lang dune 2.0)
+  > EOF
+
   $ cat > dune <<EOF
   > (rule
   >   (mode promote)