test(melange): promote in source with multiple module systems (#12703)

Signed-off-by: Antonio Nuno Monteiro <[email protected]>

Author: anmonteiro

test/blackbox-tests/test-cases/melange/module-systems-in-source.t

@@ -0,0 +1,65 @@
+Test multiple module systems with promotion in-source
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.21)
+  > (using melange 1.0)
+  > EOF
+
+  $ cat > dune <<EOF
+  > (melange.emit
+  >  (alias mel)
+  >  (target output)
+  >  (emit_stdlib false)
+  >  (promote (until-clean))
+  >  (module_systems
+  >   (commonjs mel.js)
+  >   (esm mjs)))
+  > EOF
+  $ cat > main.ml <<EOF
+  > let () = Js.log "hello"
+  > EOF
+
+  $ dune build @mel
+
+Outputs both module systems
+
+  $ ls _build/default/output
+  main.mel.js
+  main.mjs
+  $ node _build/default/output/main.mel.js
+  hello
+  $ node _build/default/output/main.mjs
+  hello
+
+  $ find . -type f -not -path "./_build/*" | sort
+  ./dune
+  ./dune-project
+  ./main.mel.js
+  ./main.mjs
+  ./main.ml
+
+  $ dune clean
+  $ cat > dune <<EOF
+  > (melange.emit
+  >  (alias mel)
+  >  (target output)
+  >  (emit_stdlib false)
+  >  (promote
+  >   (until-clean)
+  >   (into ./output))
+  >  (module_systems
+  >   (commonjs mel.js)
+  >   (esm mjs)))
+  > EOF
+  $ cat > main.ml <<EOF
+  > let () = Js.log "hello"
+  > EOF
+
+  $ dune build @mel
+
+  $ find . -type f -not -path "./_build/*" | sort
+  ./dune
+  ./dune-project
+  ./main.ml
+  ./output/main.mel.js
+  ./output/main.mjs