Improve dune lang version not supported error message

src/dune_sexp/syntax.ml

@@ -423,26 +423,43 @@ let check_supported ~dune_lang_ver t (loc, ver) =
           please_port_message
       ]
   | `Unsupported_in_project (supported_ranges, min_lang_ver) ->
+    let lang_or_ext =
+      match String.equal t.name "dune" with
+      | true -> `Language
+      | false -> `Extension
+    in
     let dune_ver_text v =
-      Printf.sprintf "version %s of the dune language" (Version.to_string v)
+      match lang_or_ext with
+      | `Language -> Printf.sprintf "version %s of dune" (Version.to_string v)
+      | `Extension ->
+        Printf.sprintf "version %s of the dune language" (Version.to_string v)
     in
-    let until =
-      match min_lang_ver with
-      | Some v -> Printf.sprintf " until %s" (dune_ver_text v)
-      | None -> ""
+    let the_what =
+      match lang_or_ext with
+      | `Language -> Printf.sprintf "the %s language" t.name
+      | `Extension -> Printf.sprintf "the %s extension" t.name
     in
     let supported =
-      (if List.is_empty supported_ranges
-       then Pp.textf "There are no supported versions of this extension in %s."
-       else Pp.textf "Supported versions of this extension in %s:")
-        (dune_ver_text dune_lang_ver)
+      match List.is_empty supported_ranges with
+      | true ->
+        Pp.textf
+          "There are no supported versions of %s in %s."
+          the_what
+          (dune_ver_text dune_lang_ver)
+      | false ->
+        Pp.textf
+          "Supported versions of %s in %s are:"
+          the_what
+          (dune_ver_text dune_lang_ver)
     in
     let message =
       [ Pp.textf
           "Version %s of %s is not supported%s."
           (Version.to_string ver)
-          t.desc
-          until
+          the_what
+          (match min_lang_ver with
+           | Some v -> Printf.sprintf " until %s" (dune_ver_text v)
+           | None -> "")
       ; supported
       ; Pp.enumerate supported_ranges ~f:(fun (a, b) ->
           let open Version.Infix in
@@ -451,7 +468,7 @@ let check_supported ~dune_lang_ver t (loc, ver) =
           else Pp.textf "%s to %s" (Version.to_string a) (Version.to_string b))
       ]
     in
-    let is_error = String.is_empty until || dune_lang_ver >= (2, 6) in
+    let is_error = Option.is_none min_lang_ver || dune_lang_ver >= (2, 6) in
     User_warning.emit ~is_error ~loc message
 ;;
 

src/dune_sexp/versioned_file.ml

@@ -57,21 +57,24 @@ struct
 
     let parse first_line : Instance.t =
       let { First_line.lang = name_loc, name; version = ver_loc, ver } = first_line in
-      let dune_lang_ver =
-        Decoder.parse
-          Syntax.Version.decode
-          Univ_map.empty
-          (Atom (ver_loc, Atom.of_string ver))
-      in
       match Table.find langs name with
       | None ->
         User_error.raise
           ~loc:name_loc
           [ Pp.textf "Unknown language %S." name ]
           ~hints:(User_message.did_you_mean name ~candidates:(Table.keys langs))
       | Some t ->
-        Syntax.check_supported ~dune_lang_ver t.syntax (ver_loc, dune_lang_ver);
-        { syntax = t.syntax; data = t.data; version = dune_lang_ver }
+        let version =
+          Decoder.parse
+            Syntax.Version.decode
+            Univ_map.empty
+            (Atom (ver_loc, Atom.of_string ver))
+        in
+        Syntax.check_supported
+          ~dune_lang_ver:(Syntax.greatest_supported_version_exn t.syntax)
+          t.syntax
+          (ver_loc, version);
+        { syntax = t.syntax; data = t.data; version }
     ;;
 
     (* TODO get_exn is only called with "dune" so far, but

test/blackbox-tests/test-cases/cinaps/link-flags.t

@@ -29,7 +29,8 @@ Check that the version guard is correct.
                     ^^^
   Error: Version 1.3 of the cinaps extension is not supported until version 3.8
   of the dune language.
-  Supported versions of this extension in version 3.7 of the dune language:
+  Supported versions of the cinaps extension in version 3.7 of the dune
+  language are:
   - 1.0 to 1.2
   [1]
 

test/blackbox-tests/test-cases/extensions-versioning/version-mismatch.t/run.t

@@ -6,6 +6,7 @@ Test that version of extensions is compatible with dune_lang version
                     ^^^
   Warning: Version 2.0 of the menhir extension is not supported until version
   1.4 of the dune language.
-  Supported versions of this extension in version 1.2 of the dune language:
+  Supported versions of the menhir extension in version 1.2 of the dune
+  language are:
   - 1.0
 

test/blackbox-tests/test-cases/extensions-versioning/version-unknown-2.5.t/run.t

@@ -6,7 +6,8 @@ version-mismatch.t
   2 | (using menhir 4.0)
                     ^^^
   Error: Version 4.0 of the menhir extension is not supported.
-  Supported versions of this extension in version 2.5 of the dune language:
+  Supported versions of the menhir extension in version 2.5 of the dune
+  language are:
   - 1.0 to 1.1
   - 2.0 to 2.1
   [1]

test/blackbox-tests/test-cases/extensions-versioning/version-unknown.t/run.t

@@ -3,7 +3,8 @@
   2 | (using menhir 4.0)
                     ^^^
   Error: Version 4.0 of the menhir extension is not supported.
-  Supported versions of this extension in version 1.2 of the dune language:
+  Supported versions of the menhir extension in version 1.2 of the dune
+  language are:
   - 1.0
   [1]
 

test/blackbox-tests/test-cases/foreign-stubs/fs-mode-dependent/fsmd-exe.t/run.t

@@ -25,10 +25,10 @@ But the toggle only exists in Dune 3.5
   File "dune-project", line 2, characters 27-30:
   2 | (using mode_specific_stubs 0.1)
                                  ^^^
-  Error: Version 0.1 of syntax extension for mode-specific foreign stubs is not
-  supported until version 3.5 of the dune language.
-  There are no supported versions of this extension in version 3.1 of the dune
-  language.
+  Error: Version 0.1 of the mode_specific_stubs extension is not supported
+  until version 3.5 of the dune language.
+  There are no supported versions of the mode_specific_stubs extension in
+  version 3.1 of the dune language.
 
   [1]
 

test/blackbox-tests/test-cases/lang-dune-warning.t

@@ -52,3 +52,20 @@ And without suffix it is accepted.
   > EOF
 
   $ dune build
+
+If a new version of dune lang is encountered, we print a helpful error message
+to the user:
+
+  $ cat > dune-project << EOF
+  > (lang dune 123.123)
+  > EOF
+
+  $ dune build 2>&1 | sed -E 's/ 3.[0-9]+/ 3.XX/g'
+  File "dune-project", line 1, characters 11-18:
+  1 | (lang dune 123.123)
+                 ^^^^^^^
+  Error: Version 123.123 of the dune language is not supported.
+  Supported versions of the dune language in version 3.XX of dune are:
+  - 1.0 to 1.12
+  - 2.0 to 2.9
+  - 3.XX to 3.XX

test/blackbox-tests/test-cases/mdx-stanza/lang-version.t/run.t

@@ -9,10 +9,10 @@ The MDX stanza requires dune lang 2.4 or higher
   File "dune-project", line 2, characters 11-14:
   2 | (using mdx 0.1)
                  ^^^
-  Warning: Version 0.1 of mdx extension to verify code blocks in .md files is
-  not supported until version 2.4 of the dune language.
-  There are no supported versions of this extension in version 2.3 of the dune
-  language.
+  Warning: Version 0.1 of the mdx extension is not supported until version 2.4
+  of the dune language.
+  There are no supported versions of the mdx extension in version 2.3 of the
+  dune language.
 
   File "dune", line 1, characters 0-5:
   1 | (mdx)
@@ -32,8 +32,9 @@ The version 0.2 requires dune 3.0
   File "dune-project", line 2, characters 11-14:
   2 | (using mdx 0.2)
                  ^^^
-  Error: Version 0.2 of mdx extension to verify code blocks in .md files is not
-  supported until version 3.0 of the dune language.
-  Supported versions of this extension in version 2.9 of the dune language:
+  Error: Version 0.2 of the mdx extension is not supported until version 3.0 of
+  the dune language.
+  Supported versions of the mdx extension in version 2.9 of the dune language
+  are:
   - 0.1
   [1]

test/blackbox-tests/test-cases/mdx-stanza/mld-files.t

@@ -90,9 +90,10 @@ the stanza version.
   File "dune-project", line 2, characters 11-14:
   2 | (using mdx 0.4)
                  ^^^
-  Error: Version 0.4 of mdx extension to verify code blocks in .md files is not
-  supported until version 3.8 of the dune language.
-  Supported versions of this extension in version 3.7 of the dune language:
+  Error: Version 0.4 of the mdx extension is not supported until version 3.8 of
+  the dune language.
+  Supported versions of the mdx extension in version 3.7 of the dune language
+  are:
   - 0.1 to 0.3
   [1]
 

test/blackbox-tests/test-cases/menhir/explain.t/run.t

@@ -31,7 +31,8 @@ First we check the version guards:
                     ^^^
   Error: Version 3.0 of the menhir extension is not supported until version
   3.13 of the dune language.
-  Supported versions of this extension in version 3.12 of the dune language:
+  Supported versions of the menhir extension in version 3.12 of the dune
+  language are:
   - 1.0 to 1.1
   - 2.0 to 2.1
   [1]

test/blackbox-tests/test-cases/pkg/pin-stanza/unknown-dune-version.t

@@ -28,7 +28,7 @@ We are unable to pin projects that the version of dune doesn't understand.
   1 | (lang dune 3.XX)
                  ^^^^^
   Error: Version 100.1 of the dune language is not supported.
-  Supported versions of this extension in version 100.1 of the dune language:
+  Supported versions of the dune language in version 3.XX of dune are:
   - 1.0 to 1.12
   - 2.0 to 2.9
   - 3.XX to 3.XX