Better "since" error messages

src/dune/dune_file.ml

@@ -23,7 +23,7 @@ let relative_file =
 let library_variants =
   let syntax =
     Dune_lang.Syntax.create ~name:"library_variants"
-      ~desc:"the experimental library variants feature."
+      ~desc:"the experimental library variants feature"
       [ ((0, 1), `Since (1, 9)); ((0, 2), `Since (1, 11)) ]
   in
   Dune_project.Extension.register_simple ~experimental:true syntax

src/dune_lang/syntax.ml

@@ -137,10 +137,17 @@ type t =
 
 module Error_msg = struct
   let since t ver ~what =
+    let lang_or_using =
+      if t.name = "dune" then
+        "lang"
+      else
+        "using"
+    in
     Printf.sprintf
       "%s is only available since version %s of %s. Please update your \
-       dune-project file to have (lang %s)."
-      what (Version.to_string ver) t.desc (Version.to_string ver)
+       dune-project file to have (%s %s %s)."
+      what (Version.to_string ver) t.desc lang_or_using t.name
+      (Version.to_string ver)
 end
 
 module Error = struct

test/blackbox-tests/dune.inc

@@ -1040,6 +1040,14 @@
    test-cases/github3180
    (progn (run dune-cram run run.t) (diff? run.t run.t.corrected)))))
 
+(rule
+ (alias github3412)
+ (deps (package dune) (source_tree test-cases/github3412))
+ (action
+  (chdir
+   test-cases/github3412
+   (progn (run dune-cram run run.t) (diff? run.t run.t.corrected)))))
+
 (rule
  (alias github534)
  (deps (package dune) (source_tree test-cases/github534))
@@ -2567,6 +2575,7 @@
   (alias github2848)
   (alias github3046)
   (alias github3180)
+  (alias github3412)
   (alias github534)
   (alias github568)
   (alias github597)
@@ -2852,6 +2861,7 @@
   (alias github2848)
   (alias github3046)
   (alias github3180)
+  (alias github3412)
   (alias github534)
   (alias github568)
   (alias github597)

test/blackbox-tests/test-cases/copy-files-non-sub-dir-error/run.t

@@ -7,5 +7,5 @@ version that introduced this feature:
                   ^^^^^^^^^^^^
   Error: to_copy/* is not a sub-directory of src. This is only available since
   version 1.3 of the dune language. Please update your dune-project file to
-  have (lang 1.3).
+  have (lang dune 1.3).
   [1]

test/blackbox-tests/test-cases/dune-project-meta/run.t

@@ -328,7 +328,7 @@ Not supported before 2.1:
   6 |  (depends (conf-libX11 (<> :os win32))))
                              ^^^^^^^^^^^^^^
   Error: Passing two arguments to <> is only available since version 2.1 of the
-  dune language. Please update your dune-project file to have (lang 2.1).
+  dune language. Please update your dune-project file to have (lang dune 2.1).
   [1]
 
 Supported since 2.1:

test/blackbox-tests/test-cases/foreign-library/run.t

@@ -25,7 +25,7 @@ Testsuite for the (foreign_library ...) stanza.
   2 |  (language c)
   3 |  (names add))
   Error: 'foreign_library' is only available since version 2.0 of the dune
-  language. Please update your dune-project file to have (lang 2.0).
+  language. Please update your dune-project file to have (lang dune 2.0).
   [1]
 
 ----------------------------------------------------------------------------------

test/blackbox-tests/test-cases/github3412/dune

@@ -0,0 +1,3 @@
+(library
+  (name toto)
+  (variant x))

test/blackbox-tests/test-cases/github3412/dune-project

@@ -0,0 +1 @@
+(lang dune 2.5)

test/blackbox-tests/test-cases/github3412/run.t

@@ -0,0 +1,8 @@
+  $ dune build
+  File "dune", line 3, characters 2-13:
+  3 |   (variant x))
+        ^^^^^^^^^^^
+  Error: 'variant' is only available since version 0.1 of the experimental
+  library variants feature. Please update your dune-project file to have (using
+  library_variants 0.1).
+  [1]

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

@@ -83,7 +83,7 @@ TODO: Fix %{libexec} and %{libexec-private} variables and test them.
   3 |  (action (echo "%{lib-private:private_lib:a.ml}")))
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   Error: %{lib-private:..} is only available since version 2.1 of the dune
-  language. Please update your dune-project file to have (lang 2.1).
+  language. Please update your dune-project file to have (lang dune 2.1).
   [1]
 
 ----------------------------------------------------------------------------------

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

@@ -25,7 +25,7 @@ It also requires dune lang 2.4 or higher
   1 | (mdx)
       ^^^^^
   Error: 'mdx' is only available since version 2.4 of the dune language. Please
-  update your dune-project file to have (lang 2.4).
+  update your dune-project file to have (lang dune 2.4).
   [1]
 
 You can use the mdx stanza to check your documentation in markdown and mli files

test/blackbox-tests/test-cases/tests-stanza-action-syntax-version/run.t

@@ -6,4 +6,4 @@ If there is an (action) field defined in a test stanza and dune-project sets
   3 |   (action (run %{test}))
         ^^^^^^^^^^^^^^^^^^^^^^
   Warning: 'action' is only available since version 1.2 of the dune language.
-  Please update your dune-project file to have (lang 1.2).
+  Please update your dune-project file to have (lang dune 1.2).

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

@@ -30,7 +30,7 @@ The vendored_dirs stanza is available from version 1.11 of the dune language
   1 | (vendored_dirs *)
       ^^^^^^^^^^^^^^^^^
   Error: 'vendored_dirs' is only available since version 1.11 of the dune
-  language. Please update your dune-project file to have (lang 1.11).
+  language. Please update your dune-project file to have (lang dune 1.11).
   [1]
 
 The same directory cannot be marked as both vendored and data-only

test/blackbox-tests/test-cases/with-unsupported-nested-exit-codes/run.t

@@ -25,5 +25,5 @@
   10 |            (run ./exit.exe 1)))))
   Error: nesting modifiers under 'with-accepted-exit-codes' is only available
   since version 2.2 of the dune language. Please update your dune-project file
-  to have (lang 2.2).
+  to have (lang dune 2.2).
   [1]