unikernel/duniverse/dune_/test/blackbox-tests/test-cases/melange/root-module.t

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+A library can be shadowed by an internal module name:
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.8)
+  > (using melange 0.1)
+  > EOF
+
+  $ mkdir lib1 lib2
+
+  $ cat >lib1/dune <<EOF
+  > (library
+  >  (name lib1)
+  >  (modes melange))
+  > EOF
+  $ cat >lib1/lib1.ml <<EOF
+  > let greeting = "Hello World"
+  > EOF
+
+  $ cat >lib2/dune <<EOF
+  > (library
+  >  (libraries lib1)
+  >  (name lib2)
+  >  (modes melange))
+  > EOF
+
+Now we shadow lib1:
+  $ cat >lib2/lib1.ml <<EOF
+  > let greeting = ()
+  > EOF
+  $ cat >lib2/lib2.ml <<EOF
+  > print_endline Lib1.greeting
+  > EOF
+
+  $ dune build lib2/.lib2.objs/melange/lib2.cmj
+  File "lib2/lib2.ml", line 1, characters 14-27:
+  1 | print_endline Lib1.greeting
+                    ^^^^^^^^^^^^^
+  Error: The value Lib1.greeting has type unit
+         but an expression was expected of type string
+  [1]
+
+We can use root_module to use lib1 with a different name:
+
+  $ cat >lib2/dune <<EOF
+  > (library
+  >  (libraries lib1)
+  >  (root_module root)
+  >  (name lib2)
+  >  (modes melange))
+  > EOF
+  $ cat >lib2/lib2.ml <<EOF
+  > let () = print_endline Root.Lib1.greeting
+  > EOF
+  $ dune build lib2/.lib2.objs/melange/lib2.cmj
+
+The same for melange.emit:
+
+  $ cat > dune <<EOF
+  > (melange.emit
+  >  (alias mel)
+  >  (target output)
+  >  (libraries lib1)
+  >  (emit_stdlib false)
+  >  (root_module root))
+  > EOF
+  $ cat > lib1.ml <<EOF
+  > let greeting = ()
+  > EOF
+  $ cat >foo.ml <<EOF
+  > print_endline Lib1.greeting
+  > EOF
+  $ dune build output/foo.js
+  File "foo.ml", line 1, characters 14-27:
+  1 | print_endline Lib1.greeting
+                    ^^^^^^^^^^^^^
+  Error: The value Lib1.greeting has type unit
+         but an expression was expected of type string
+  [1]
+
+Use root_module to fix:
+
+  $ cat >foo.ml <<EOF
+  > print_endline Root.Lib1.greeting
+  > EOF
+  $ dune build @mel
+  $ node _build/default/output/foo.js
+  Hello World