unikernel/duniverse/dune_/test/blackbox-tests/test-cases/meta-exports.t

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+Check our handling of `exports` in META files. We begin with a test showing that
+we can *consume* META files containing an `exports` field.
+
+To do this, first we create a Findlib hierarchy containing two installed
+packages, `foo` and `bar`. The package `foo` is empty and only exists to
+re-export `bar`. The package `bar` consists of a bytecode library, `bar.cma`.
+
+  $ mkdir -p _install/foo
+  $ cat >_install/foo/META <<EOF
+  > requires = "bar"
+  > EOF
+
+  $ mkdir -p _install/bar
+  $ cat >_install/bar/META <<EOF
+  > archive(byte) = "bar.cma"
+  > EOF
+  $ cat >_install/bar/bar.ml <<EOF
+  > let x = 42
+  > EOF
+  $ ocamlc -a -o _install/bar/bar.cma _install/bar/bar.ml
+
+We now define a Dune project that will consume `foo`.
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.0)
+  > EOF
+
+  $ cat >dune <<EOF
+  > (executable
+  >  (name main)
+  >  (modes byte)
+  >  (libraries foo))
+  > EOF
+  $ cat >main.ml <<EOF
+  > let () = print_int Bar.x; print_newline ()
+  > EOF
+
+Compilation works with `(implicit_transitive_deps)`:
+
+  $ OCAMLPATH=$(pwd)/_install dune exec ./main.exe
+  42
+
+However, the compilation without `(implicit_transitive_deps)` fails:
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.0)
+  > (implicit_transitive_deps false)
+  > EOF
+
+  $ OCAMLPATH=$(pwd)/_install dune exec ./main.exe
+  File "main.ml", line 1, characters 19-24:
+  1 | let () = print_int Bar.x; print_newline ()
+                         ^^^^^
+  Error: Unbound module Bar
+  [1]
+
+Next, we add the `exports` field to `foo`'s `META` file:
+
+  $ cat >_install/foo/META <<EOF
+  > requires = "bar"
+  > exports = "bar"
+  > EOF
+
+and compilation now works again:
+
+  $ OCAMLPATH=$(pwd)/_install dune exec ./main.exe
+  42
+
+----------------------------------------------------------------
+
+Next, we check that we can *produce* META files with the `export` field.  To do
+this, we define two Dune libraries `foo` and `bar`, where `foo` depends on `bar`
+using `(re_export)`.
+
+  $ cat >dune-project.gen <<'EOF'
+  > cat <<EOF2
+  > (lang dune $VERSION)
+  > (package (name foo))
+  > (package (name bar))
+  > EOF2
+  > EOF
+
+  $ cat >dune <<EOF
+  > (library
+  >  (public_name bar)
+  >  (modules bar))
+  > (library
+  >  (public_name foo)
+  >  (libraries (re_export bar))
+  >  (modules foo))
+  > EOF
+  $ true >bar.ml
+  $ true >foo.ml
+
+First we try with dune version 3.16 (it should not generate the `exports` field):
+
+  $ VERSION=3.16 sh dune-project.gen >dune-project
+  $ dune build && dune install --libdir $(pwd)/_local --prefix $(pwd)
+  $ cat _local/foo/META
+  description = ""
+  requires = "bar"
+  archive(byte) = "foo.cma"
+  archive(native) = "foo.cmxa"
+  plugin(byte) = "foo.cma"
+  plugin(native) = "foo.cmxs"
+
+Now with dune version 3.17 (it should generate the `exports` field):
+
+  $ VERSION=3.17 sh dune-project.gen >dune-project
+  $ dune build && dune install --libdir $(pwd)/_local --prefix $(pwd)
+  $ cat _local/foo/META
+  description = ""
+  requires = "bar"
+  exports = "bar"
+  archive(byte) = "foo.cma"
+  archive(native) = "foo.cmxa"
+  plugin(byte) = "foo.cma"
+  plugin(native) = "foo.cmxs"