Private/Public overlap tests

private dependencies aren't allowed in public libraries. These tests
demonstrates that dune accepts them anyway

test/blackbox-tests/jbuild

@@ -419,3 +419,14 @@
      (progn
       (run ${exe:cram.exe} run.t)
       (diff? run.t run.t.corrected)))))))
+
+
+(alias
+ ((name runtest)
+  (deps ((files_recursively_in test-cases/private-public-overlap)))
+  (action
+   (chdir test-cases/private-public-overlap
+    (setenv JBUILDER ${bin:jbuilder}
+     (progn
+      (run ${exe:cram.exe} run.t)
+      (diff? run.t run.t.corrected)))))))

test/blackbox-tests/test-cases/private-public-overlap/exes/jbuild

@@ -0,0 +1,11 @@
+(jbuild_version 1)
+
+(library
+ ((name privatelib)
+  (modules (privatelib))))
+
+(executable
+ ((name publicbin)
+  (modules (publicbin))
+  (public_name publicbin)
+  (package publicbin)))

test/blackbox-tests/test-cases/private-public-overlap/private-dep/jbuild

@@ -0,0 +1,11 @@
+(jbuild_version 1)
+
+(library
+ ((name privatelib)
+  (modules (privatelib))))
+
+(library
+ ((name publiclib)
+  (public_name publiclib)
+  (libraries (privatelib))
+  (modules (publiclib))))

test/blackbox-tests/test-cases/private-public-overlap/private-rewriter/jbuild

@@ -0,0 +1,12 @@
+(jbuild_version 1)
+
+(library
+ ((name ppx_internal)
+  (modules (:standard \ mylib))
+  (kind ppx_rewriter)))
+
+(library
+ ((name mylib)
+  (public_name mylib)
+  (preprocess (pps (ppx_internal)))
+  (modules (mylib))))

test/blackbox-tests/test-cases/private-public-overlap/private-runtime-deps/jbuild

@@ -0,0 +1,17 @@
+(jbuild_version 1)
+
+(library
+ ((name private_runtime_dep)
+  (modules (private_runtime_dep))))
+
+(library
+ ((name private_ppx)
+  (kind ppx_rewriter)
+  (ppx_runtime_libraries (private_runtime_dep))
+  (modules (:standard \ mylib private_runtime_dep))))
+
+(library
+ ((name mylib)
+  (public_name mylib)
+  (preprocess (pps (private_ppx)))
+  (modules (mylib))))

test/blackbox-tests/test-cases/private-public-overlap/run.t

@@ -0,0 +1,50 @@
+public libraries may not have private dependencies
+
+  $ $JBUILDER build -j1 --display short --root private-dep 2>&1 | grep -v Entering
+      ocamldep publiclib.ml.d
+      ocamldep privatelib.ml.d
+        ocamlc .privatelib.objs/privatelib.{cmi,cmo,cmt}
+        ocamlc .publiclib.objs/publiclib.{cmi,cmo,cmt}
+        ocamlc publiclib.cma
+      ocamlopt .privatelib.objs/privatelib.{cmx,o}
+      ocamlopt .publiclib.objs/publiclib.{cmx,o}
+      ocamlopt publiclib.{a,cmxa}
+      ocamlopt publiclib.cmxs
+
+On the other hand, public libraries may have private preprocessors
+  $ $JBUILDER build -j1 --display short --root private-rewriter 2>&1 | grep -v Entering
+        ocamlc .ppx_internal.objs/ppx_internal.{cmi,cmo,cmt}
+      ocamlopt .ppx_internal.objs/ppx_internal.{cmx,o}
+      ocamlopt ppx_internal.{a,cmxa}
+      ocamlopt .ppx/ppx_internal@mylib/ppx.exe
+           ppx mylib.pp.ml
+      ocamldep mylib.pp.ml.d
+        ocamlc .mylib.objs/mylib.{cmi,cmo,cmt}
+      ocamlopt .mylib.objs/mylib.{cmx,o}
+      ocamlopt mylib.{a,cmxa}
+      ocamlopt mylib.cmxs
+        ocamlc mylib.cma
+
+Unless they introduce private runtime dependencies:
+  $ $JBUILDER build -j1 --display short --root private-runtime-deps 2>&1 | grep -v Entering
+        ocamlc .private_ppx.objs/private_ppx.{cmi,cmo,cmt}
+      ocamlopt .private_ppx.objs/private_ppx.{cmx,o}
+      ocamlopt private_ppx.{a,cmxa}
+      ocamlopt .ppx/private_ppx@mylib/ppx.exe
+           ppx mylib.pp.ml
+      ocamldep mylib.pp.ml.d
+      ocamldep private_runtime_dep.ml.d
+        ocamlc .private_runtime_dep.objs/private_runtime_dep.{cmi,cmo,cmt}
+        ocamlc .mylib.objs/mylib.{cmi,cmo,cmt}
+        ocamlc mylib.cma
+      ocamlopt .private_runtime_dep.objs/private_runtime_dep.{cmx,o}
+      ocamlopt .mylib.objs/mylib.{cmx,o}
+      ocamlopt mylib.{a,cmxa}
+      ocamlopt mylib.cmxs
+
+However, public binaries may accept private dependencies
+  $ $JBUILDER build -j1 --display short --root exes 2>&1 | grep -v Entering
+      ocamldep publicbin.ml.d
+        ocamlc .publicbin.eobjs/publicbin.{cmi,cmo,cmt}
+      ocamlopt .publicbin.eobjs/publicbin.{cmx,o}
+      ocamlopt publicbin.exe