Hid generated-code-only headers inside a separate library.

BUILD

@@ -50,7 +50,11 @@ cc_library(
     srcs = [
         "upb/decode.c",
         "upb/encode.c",
+        "upb/generated_util.h",
         "upb/msg.c",
+        "upb/msg.h",
+        "upb/port_def.inc",
+        "upb/port_undef.inc",
         "upb/table.c",
         "upb/table.int.h",
         "upb/upb.c",
@@ -58,16 +62,30 @@ cc_library(
     hdrs = [
         "upb/decode.h",
         "upb/encode.h",
-        "upb/generated_util.h",
-        "upb/msg.h",
         "upb/upb.h",
     ],
     copts = COPTS,
-    # Internal-only, but we have to make them public for generated code.
+    visibility = ["//visibility:public"],
+)
+
+# Common support routines used by generated code.  This library has no
+# implementation, but depends on :upb and exposes a few more hdrs.
+#
+# This is public only because we have no way of visibility-limiting it to
+# upb_proto_library() only.  This interface is not stable and by using it you
+# give up any backward compatibility guarantees.
+cc_library(
+    name = "generated_code_support__only_for_generated_code_do_not_use__i_give_permission_to_break_me",
     textual_hdrs = [
         "upb/port_def.inc",
         "upb/port_undef.inc",
     ],
+    hdrs = [
+        "upb/generated_util.h",
+        "upb/msg.h",
+    ],
+    deps = [":upb"],
+    copts = COPTS,
     visibility = ["//visibility:public"],
 )
 

CMakeLists.txt

@@ -63,15 +63,20 @@ enable_testing()
 add_library(upb
   upb/decode.c
   upb/encode.c
+  upb/generated_util.h
   upb/msg.c
+  upb/msg.h
+  upb/port_def.inc
+  upb/port_undef.inc
   upb/table.c
   upb/table.int.h
   upb/upb.c
   upb/decode.h
   upb/encode.h
-  upb/generated_util.h
-  upb/msg.h
   upb/upb.h)
+add_library(generated_code_support__only_for_generated_code_do_not_use__i_give_permission_to_break_me INTERFACE)
+target_link_libraries(generated_code_support__only_for_generated_code_do_not_use__i_give_permission_to_break_me INTERFACE
+  upb)
 add_library(reflection
   upb/def.c
   upb/msgfactory.c

bazel/upb_proto_library.bzl

@@ -229,7 +229,10 @@ _upb_proto_library_aspect = aspect(
         "_cc_toolchain": attr.label(
             default = "@bazel_tools//tools/cpp:current_cc_toolchain",
         ),
-        "_upb": attr.label_list(default = ["//:upb"]),
+        "_upb": attr.label_list(default = [
+            "//:generated_code_support__only_for_generated_code_do_not_use__i_give_permission_to_break_me",
+            "//:upb"
+        ]),
         "_ext": attr.string(default = ".upb"),
     }),
     implementation = _upb_proto_aspect_impl,