feature: allow arch_sixtyfour in enabled_if

Signed-off-by: Ali Caglayan <alizter@gmail.com>

CHANGES.md

@@ -9,6 +9,9 @@ Unreleased
 - Add `dune show` command group which is an alias of `dune describe`. (#7946,
   @Alizter)
 
+- `enabled_if` now supports `arch_sixtyfour` variable (#8023, fixes #7997,
+  @Alizter)
+
 - Include source tree scans in the traces produced by `--trace-file` (#7937,
   @rgrinberg)
 

src/dune_rules/enabled_if.ml

@@ -18,6 +18,7 @@ let common_vars_list =
   ; "profile"
   ; "ocaml_version"
   ; "context_name"
+  ; "arch_sixtyfour"
   ]
 
 let common_vars ~since =
@@ -26,6 +27,7 @@ let common_vars ~since =
        ~f:(fun var ->
          match var with
          | "context_name" -> (var, (2, 7))
+         | "arch_sixtyfour" -> (var, (3, 9))
          | _ -> (var, since))
        common_vars_list)
 

test/blackbox-tests/test-cases/enabled_if/eif-arch_sixtyfour.t/dune

@@ -0,0 +1,4 @@
+(executable
+ (name hello)
+ (enabled_if
+  (= %{arch_sixtyfour} %{arch_sixtyfour})))

test/blackbox-tests/test-cases/enabled_if/eif-arch_sixtyfour.t/hello.ml

@@ -0,0 +1 @@
+let () = Printf.printf "Hello, World!\n"

test/blackbox-tests/test-cases/enabled_if/eif-arch_sixtyfour.t/run.t

@@ -0,0 +1,31 @@
+Testing %{arch_sixtyfour} in enabled_if
+
+  $ cat > dune-project << EOF
+  > (lang dune 3.9)
+  > EOF
+
+  $ dune exec -- ./hello.exe
+  Hello, World!
+
+Testing the version guard
+
+  $ cat > dune-project << EOF
+  > (lang dune 3.8)
+  > EOF
+
+  $ dune exec -- ./hello.exe
+  File "dune", line 4, characters 2-41:
+  4 |   (= %{arch_sixtyfour} %{arch_sixtyfour})))
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  Error: Unexpected list
+  [1]
+
+The error message is not ideal. It should say something like this instead:
+
+File "dune", line 3, characters 13-30:
+3 |  (enabled_if %{arch_sixtyfour}))
+Error: %{arch_sixtyfour} is only available since version 3.9 of the dune
+language. Please update your dune-project file to have (lang dune 3.9).
+[1]
+
+However, for now, the version guard works.