go_proto_library: drop dependencies on APIv1 WKT packages (#2740)

Since protobuf 3.14, the Well Known Types declare APIv2 package paths,
which means generated code that imports them will import APIv2
packages.

Fixes #2721

README.rst

@@ -438,9 +438,12 @@ To generate code from protocol buffers, you'll need to add a dependency on
 
     http_archive(
         name = "com_google_protobuf",
-        sha256 = "9748c0d90e54ea09e5e75fb7fac16edce15d2028d4356f32211cfa3c0e956564",
-        strip_prefix = "protobuf-3.11.4",
-        urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.11.4.zip"],
+        sha256 = "d0f5f605d0d656007ce6c8b5a82df3037e1d8fe8b121ed42e536f569dec16113",
+        strip_prefix = "protobuf-3.14.0",
+        urls = [
+            "https://mirror.bazel.build/github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
+            "https://github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
+        ],
     )
 
     load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")

go/dependencies.rst

@@ -119,19 +119,23 @@ Proto dependencies
 ------------------
 
 In order to build `proto_library`_ and `go_proto_library`_ rules, you must
-add a dependency on ``com_google_protobuf`` (perhaps on a newer version)
-in order to build the ``protoc`` compiler. You'll need a C/C++ toolchain for
-the execution platform, too.
+add a dependency on ``com_google_protobuf`` in order to build the ``protoc``
+compiler. Version 3.14.0 is the minimum supported version, but higher minor
+versions shoudl work. You'll need a C/C++ toolchain for the execution platform
+to build ``protoc``.
 
 .. code:: bzl
 
     load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
     http_archive(
         name = "com_google_protobuf",
-        sha256 = "9748c0d90e54ea09e5e75fb7fac16edce15d2028d4356f32211cfa3c0e956564",
-        strip_prefix = "protobuf-3.11.4",
-        urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.11.4.zip"],
+        sha256 = "d0f5f605d0d656007ce6c8b5a82df3037e1d8fe8b121ed42e536f569dec16113",
+        strip_prefix = "protobuf-3.14.0",
+        urls = [
+            "https://mirror.bazel.build/github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
+            "https://github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
+        ],
     )
 
     load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")
@@ -225,9 +229,12 @@ For example, this is how you would override ``com_github_golang_protobuf``:
 
     http_archive(
         name = "com_google_protobuf",
-        sha256 = "9748c0d90e54ea09e5e75fb7fac16edce15d2028d4356f32211cfa3c0e956564",
-        strip_prefix = "protobuf-3.11.4",
-        urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.11.4.zip"],
+        sha256 = "d0f5f605d0d656007ce6c8b5a82df3037e1d8fe8b121ed42e536f569dec16113",
+        strip_prefix = "protobuf-3.14.0",
+        urls = [
+            "https://mirror.bazel.build/github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
+            "https://github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
+        ],
     )
 
     load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")

proto/BUILD.bazel

@@ -20,14 +20,14 @@ go_proto_compiler(
 go_proto_compiler(
     name = "go_proto",
     visibility = ["//visibility:public"],
-    deps = PROTO_RUNTIME_DEPS + WELL_KNOWN_TYPE_RULES.values() + WELL_KNOWN_TYPES_APIV2,
+    deps = PROTO_RUNTIME_DEPS + WELL_KNOWN_TYPES_APIV2,
 )
 
 go_proto_compiler(
     name = "go_grpc",
     options = ["plugins=grpc"],
     visibility = ["//visibility:public"],
-    deps = PROTO_RUNTIME_DEPS + WELL_KNOWN_TYPE_RULES.values() + WELL_KNOWN_TYPES_APIV2 + [
+    deps = PROTO_RUNTIME_DEPS + WELL_KNOWN_TYPES_APIV2 + [
         "@org_golang_google_grpc//:go_default_library",
         "@org_golang_google_grpc//codes:go_default_library",
         "@org_golang_google_grpc//status:go_default_library",

proto/wkt/well_known_types.bzl

@@ -1,13 +1,12 @@
 load("//go:def.bzl", "GoArchive", "GoLibrary", "GoSource")
-load("//proto:def.bzl", "go_proto_library")
 load("//proto:compiler.bzl", "GoProtoCompiler")
 
 _proto_library_suffix = "proto"
 _go_proto_library_suffix = "go_proto"
 
-# TODO: this should be private. Make sure nothing depends on it, then rename it.
-# TODO: remove after protoc 3.14 is the minimum supported version. The WKTs
-# changed their import paths in that version.
+# NOTE: since protobuf 3.14, the WKTs no longer use these paths. They're only
+# used by gogo below. Not clear if that actually works or if we should
+# continue supporting gogo.
 WELL_KNOWN_TYPE_PACKAGES = {
     "any": ("github.com/golang/protobuf/ptypes/any", []),
     "api": ("google.golang.org/genproto/protobuf/api", ["source_context", "type"]),
@@ -32,6 +31,7 @@ GOGO_WELL_KNOWN_TYPE_REMAPS = [
     "Mgoogle/protobuf/compiler_plugin.proto=github.com/gogo/protobuf/protoc-gen-gogo/plugin",
 ]
 
+# NOTE: only used by gogo.
 WELL_KNOWN_TYPE_RULES = {
     wkt: "@io_bazel_rules_go//proto/wkt:{}_{}".format(wkt, _go_proto_library_suffix)
     for wkt in WELL_KNOWN_TYPE_PACKAGES.keys()
@@ -45,17 +45,13 @@ PROTO_RUNTIME_DEPS = [
     "@org_golang_google_protobuf//runtime/protoimpl:go_default_library",
 ]
 
-# TODO(#2721): after com_google_protobuf 3.14 is the minimum supported version,
-# drop the implicit dependencies on WELL_KNOWN_TYPE_RULES.values() from
-# //proto/wkt:go_proto and //proto/wkt:go_grpc.
-#
 # In protobuf 3.14, the 'option go_package' declarations were changed in the
-# Well Known Types to point to the APIv2 packages. Consequently, generated
+# Well Known Types to point to the APIv2 packages below. Consequently, generated
 # proto code will import APIv2 packages instead of the APIv1 packages, even
-# when the APIv1 compiler is used (which is still the default). We shouldn't
-# need the APIv1 dependencies with protobuf 3.14, but we don't know which
-# version is in use at load time. The extra packages will be compiled but not
-# linked.
+# when the APIv1 compiler is used (which is still the default).
+#
+# protobuf 3.14 is now the minimum supported version, so we no longer depend
+# on the APIv1 packages.
 WELL_KNOWN_TYPES_APIV2 = [
     "@org_golang_google_protobuf//types/descriptorpb",
     "@org_golang_google_protobuf//types/known/anypb",
@@ -71,18 +67,6 @@ WELL_KNOWN_TYPES_APIV2 = [
     "@org_golang_google_protobuf//types/pluginpb",
 ]
 
-def gen_well_known_types():
-    for wkt, rule in WELL_KNOWN_TYPE_RULES.items():
-        (go_package, deps) = WELL_KNOWN_TYPE_PACKAGES[wkt]
-        go_proto_library(
-            name = rule.rsplit(":", 1)[1],
-            compilers = ["@io_bazel_rules_go//proto:go_proto_bootstrap"],
-            importpath = go_package,
-            proto = "@com_google_protobuf//:{}_{}".format(wkt, _proto_library_suffix),
-            visibility = ["//visibility:public"],
-            deps = [WELL_KNOWN_TYPE_RULES[dep] for dep in deps],
-        )
-
 def _go_proto_wrapper_compile(go, compiler, protos, imports, importpath):
     return []