unikernel/duniverse/dune_/test/blackbox-tests/test-cases/melange/missing-melc.t

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+Test cases when melc is not available
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.8)
+  > (using melange 0.1)
+  > EOF
+
+  $ cat > main_melange.ml <<EOF
+  > let () =
+  >   print_endline "hello from melange"
+  > EOF
+
+Set up some fake environment without melc
+
+  $ mkdir _path
+  $ ln -s $(command -v dune) _path/
+  $ ln -s $(command -v ocamlc) _path/
+  $ ln -s $(command -v ocamldep) _path/
+
+For melange.emit stanzas, an error is shown
+
+  $ cat > dune <<EOF
+  > (melange.emit
+  >  (target output)
+  >  (emit_stdlib false)
+  >  (modules main_melange)
+  >  (alias mel))
+  > EOF
+
+  $ (unset INSIDE_DUNE; PATH=_path dune build --always-show-command-line --root . @mel 2>&1 | grep Program)
+  Error: Program melc not found in the tree or in PATH
+
+For libraries, if no melange.emit stanza is found, build does not fail
+
+  $ cat > dune <<EOF
+  > (library
+  >  (name lib1)
+  >  (modules :standard \ main_native)
+  >  (modes byte melange))
+  > (executable
+  >  (name main_native)
+  >  (modules main_native)
+  >  (modes exe byte)
+  >  (libraries lib1))
+  > EOF
+
+  $ cat > main_native.ml <<EOF
+  > let () =
+  >   print_endline Lib1.Lib.t
+  > EOF
+
+  $ cat > lib.ml <<EOF
+  > let t = "hello from native"
+  > EOF
+
+  $ (unset INSIDE_DUNE; PATH=_path dune build --always-show-command-line --root . main_native.bc)
+  $ dune exec ./main_native.bc
+  hello from native
+
+If melange.emit stanza is found, but no rules are executed, build does not fail
+
+  $ cat > dune <<EOF
+  > (library
+  >  (name lib1)
+  >  (modules :standard \ main_native main_melange)
+  >  (modes byte melange))
+  > (executable
+  >  (name main_native)
+  >  (modules main_native)
+  >  (modes exe byte)
+  >  (libraries lib1))
+  > (melange.emit
+  >  (target output)
+  >  (emit_stdlib false)
+  >  (modules main_melange)
+  >  (libraries lib1))
+  > EOF
+
+  $ (unset INSIDE_DUNE; PATH=_path dune build --always-show-command-line --root . main_native.bc)
+  $ dune exec ./main_native.bc
+  hello from native
+
+But trying to build any melange artifacts will fail
+
+  $ (unset INSIDE_DUNE; PATH=_path dune build --always-show-command-line --root . output/main_melange.js)
+  File ".lib1.objs/melange/_unknown_", line 1, characters 0-0:
+  Error: Program melc not found in the tree or in PATH
+   (context: default)
+  Hint: opam install melange
+  [1]