java_grpc_library: Add support for protobuf lite

gRPC's protobuf-lite auto-selects between full and lite protobuf based on the
value of crosstool_top. If the user is specifying their own
--android_crosstool_top, then it will not auto-detect correctly. One day,
platforms will fix problems like this, but for the moment it seems we get to
live with it.

java_grpc_library.bzl

@@ -109,14 +109,15 @@ def java_grpc_library(name, srcs, deps, flavor=None,
   added_deps = [
       "@io_grpc_grpc_java//core",
       "@io_grpc_grpc_java//stub",
-      "@io_grpc_grpc_java//protobuf",
       "@com_google_guava_guava//jar",
   ]
   if flavor == "normal":
-    added_deps += ["@com_google_protobuf//:protobuf_java"]
+    added_deps += [
+        "@com_google_protobuf//:protobuf_java",
+        "@io_grpc_grpc_java//protobuf",
+    ]
   elif flavor == "lite":
-    # TODO: This is currently blocked on https://github.com/google/protobuf/issues/2762
-    added_deps += ["@com_google_protobuf_java_lite//:protobuf_java_lite"]
+    added_deps += ["@io_grpc_grpc_java//protobuf-lite"]
   else:
     fail("Unknown flavor type", "flavor")
 

protobuf-lite/BUILD.bazel

@@ -1,14 +1,26 @@
 java_library(
-    name = "protobuf_lite",
+    name = "protobuf-lite",
     srcs = glob([
         "src/main/java/**/*.java",
     ]),
-    # TOOD(zdapeng): fix visibility and deps (https://github.com/google/protobuf/issues/2762)
-    visibility = ["//protobuf:__pkg__"],
+    visibility = ["//visibility:public"],
     deps = [
         "//core",
         "@com_google_code_findbugs_jsr305//jar",
         "@com_google_guava_guava//jar",
-        "@com_google_protobuf//:protobuf_java",
-    ],
+    ] + select({
+        ":android": ["@com_google_protobuf_javalite//:protobuf_java_lite"],
+        "//conditions:default": ["@com_google_protobuf//:protobuf_java"],
+    }),
+)
+
+# This config is not fully-reliable. If it breaks, it is probably because you
+# are changing --android_crosstool_top. Instead of doing that, you can bind
+# your own toolchain on top of the default android/crosstool, as mentioned at
+# https://github.com/bazelbuild/bazel/issues/3924#issuecomment-338704582
+config_setting(
+    name = "android",
+    values = {
+        "crosstool_top": "//external:android/crosstool",
+    },
 )

protobuf/BUILD.bazel

@@ -6,7 +6,7 @@ java_library(
     visibility = ["//visibility:public"],
     deps = [
         "//core",
-        "//protobuf-lite:protobuf_lite",
+        "//protobuf-lite",
         "@com_google_api_grpc_proto_google_common_protos//jar",
         "@com_google_code_findbugs_jsr305//jar",
         "@com_google_guava_guava//jar",

repositories.bzl

@@ -9,6 +9,7 @@ def grpc_java_repositories(
     omit_com_google_guava=False,
     omit_com_google_protobuf=False,
     omit_com_google_protobuf_java=False,
+    omit_com_google_protobuf_javalite=False,
     omit_com_google_protobuf_nano_protobuf_javanano=False,
     omit_com_google_truth_truth=False,
     omit_com_squareup_okhttp=False,
@@ -45,6 +46,8 @@ def grpc_java_repositories(
     com_google_protobuf()
   if omit_com_google_protobuf_java:
     fail("omit_com_google_protobuf_java is no longer supported and must be not be passed to grpc_java_repositories()")
+  if not omit_com_google_protobuf_javalite:
+    com_google_protobuf_javalite()
   if not omit_com_google_protobuf_nano_protobuf_javanano:
     com_google_protobuf_nano_protobuf_javanano()
   if not omit_com_google_truth_truth:
@@ -146,6 +149,15 @@ def com_google_protobuf():
       urls = ["https://github.com/google/protobuf/archive/v3.5.1.zip"],
   )
 
+def com_google_protobuf_javalite():
+  # java_lite_proto_library rules implicitly depend on @com_google_protobuf_javalite
+  native.http_archive(
+      name = "com_google_protobuf_javalite",
+      sha256 = "d8a2fed3708781196f92e1e7e7e713cf66804bd2944894401057214aff4f468e",
+      strip_prefix = "protobuf-5e8916e881c573c5d83980197a6f783c132d4276",
+      urls = ["https://github.com/google/protobuf/archive/5e8916e881c573c5d83980197a6f783c132d4276.zip"],
+  )
+
 def com_google_protobuf_nano_protobuf_javanano():
   native.maven_jar(
       name = "com_google_protobuf_nano_protobuf_javanano",