Bump protobuf to 3.15.1 to work around Bazel 4 incompatibility

See also: https://github.com/bazelbuild/bazel/issues/12887

WORKSPACE

@@ -125,16 +125,16 @@ http_archive(
 # ...but the Java download is currently broken, so we use the "source" download.
 http_archive(
     name = "com_google_protobuf_javalite",
-    sha256 = "a79d19dcdf9139fa4b81206e318e33d245c4c9da1ffed21c87288ed4380426f9",
+    sha256 = "f18a40816260a9a3190a94efb0fc26270b244a2436681602f0a944739095d632",
-    strip_prefix = "protobuf-3.11.4",
+    strip_prefix = "protobuf-3.15.1",
-    urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.11.4.tar.gz"],
+    urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.15.1.tar.gz"],
 )
 
 http_archive(
     name = "com_google_protobuf",
-    sha256 = "a79d19dcdf9139fa4b81206e318e33d245c4c9da1ffed21c87288ed4380426f9",
+    sha256 = "f18a40816260a9a3190a94efb0fc26270b244a2436681602f0a944739095d632",
-    strip_prefix = "protobuf-3.11.4",
+    strip_prefix = "protobuf-3.15.1",
-    urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.11.4.tar.gz"],
+    urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.15.1.tar.gz"],
     patches = [
         "@//third_party:com_google_protobuf_fixes.diff"
     ],

third_party/com_google_protobuf_fixes.diff

@@ -1,8 +1,8 @@
 diff --git a/BUILD b/BUILD
-index 79871d621..51b3a063f 100644
+index 112432160..ab5e80ce2 100644
 --- a/BUILD
 +++ b/BUILD
-@@ -26,7 +26,7 @@ config_setting(
+@@ -50,7 +50,7 @@ GTEST_MAIN = select({
  # ZLIB configuration
  ################################################################################
  
@@ -11,7 +11,7 @@ index 79871d621..51b3a063f 100644
  
  ################################################################################
  # Protobuf Runtime Library
-@@ -157,6 +157,7 @@ cc_library(
+@@ -200,6 +200,7 @@ cc_library(
      includes = ["src/"],
      linkopts = LINK_OPTS,
      visibility = ["//visibility:public"],
@@ -19,7 +19,7 @@ index 79871d621..51b3a063f 100644
  )
  
  PROTOBUF_DEPS = select({
-@@ -230,6 +231,7 @@ cc_library(
+@@ -273,6 +274,7 @@ cc_library(
      linkopts = LINK_OPTS,
      visibility = ["//visibility:public"],
      deps = [":protobuf_lite"] + PROTOBUF_DEPS,
@@ -27,63 +27,24 @@ index 79871d621..51b3a063f 100644
  )
  
  # This provides just the header files for use in projects that need to build
-@@ -318,13 +320,13 @@ cc_proto_library(
+@@ -867,7 +869,6 @@ py_proto_library(
-
+     protoc = ":protoc",
- [native_cc_proto_library(
-     name = proto + "_cc_proto",
--    deps = [proto + "_proto"],
-     visibility = ["//visibility:private"],
-+    deps = [proto + "_proto"],
- ) for proto in WELL_KNOWN_PROTO_MAP.keys()]
-
- cc_proto_blacklist_test(
-     name = "cc_proto_blacklist_test",
--    deps = [proto + "_cc_proto" for proto in WELL_KNOWN_PROTO_MAP.keys()]
-+    deps = [proto + "_cc_proto" for proto in WELL_KNOWN_PROTO_MAP.keys()],
- )
-
- ################################################################################
-@@ -900,7 +902,6 @@ py_proto_library(
-     py_extra_srcs = glob(["python/**/__init__.py"]),
      py_libs = [
          ":python_srcs",
 -        "@six//:six",
      ],
      srcs_version = "PY2AND3",
      visibility = ["//visibility:public"],
-@@ -1002,7 +1003,9 @@ cc_library(
- # Note: We use `native_proto_common` here because we depend on an implementation-detail of
- # `proto_lang_toolchain`, which may not be available on `proto_common`.
- reject_blacklisted_files = hasattr(native_proto_common, "proto_lang_toolchain_rejects_files_do_not_use_or_we_will_break_you_without_mercy")
-+
- cc_toolchain_blacklisted_protos = [proto + "_proto" for proto in WELL_KNOWN_PROTO_MAP.keys()] if reject_blacklisted_files else [":well_known_protos"]
-+
- proto_lang_toolchain(
-     name = "cc_toolchain",
-     blacklisted_protos = cc_toolchain_blacklisted_protos,
-diff --git a/protobuf.bzl b/protobuf.bzl
-index 829464d44..4ac23594b 100644
---- a/protobuf.bzl
-+++ b/protobuf.bzl
-@@ -87,6 +87,8 @@ def _proto_gen_impl(ctx):
-     for dep in ctx.attr.deps:
-         import_flags += dep.proto.import_flags
-         deps += dep.proto.deps
-+    import_flags = depset(import_flags).to_list()
-+    deps = depset(deps).to_list()
-
-     if not ctx.attr.gen_cc and not ctx.attr.gen_py and not ctx.executable.plugin:
-         return struct(
 diff --git a/src/google/protobuf/io/gzip_stream.h b/src/google/protobuf/io/gzip_stream.h
-index b1ce1d36c..d5d560ea7 100644
+index b1ce1d36c..69ed1b996 100644
 --- a/src/google/protobuf/io/gzip_stream.h
 +++ b/src/google/protobuf/io/gzip_stream.h
-@@ -47,10 +47,12 @@
+@@ -47,10 +47,13 @@
  #include <google/protobuf/stubs/common.h>
  #include <google/protobuf/io/zero_copy_stream.h>
  #include <google/protobuf/port.h>
 -#include <zlib.h>
--
+ 
  #include <google/protobuf/port_def.inc>
  
 +#if HAVE_ZLIB
@@ -93,7 +54,7 @@ index b1ce1d36c..d5d560ea7 100644
  namespace google {
  namespace protobuf {
  namespace io {
-@@ -76,8 +78,10 @@ class PROTOBUF_EXPORT GzipInputStream : public ZeroCopyInputStream {
+@@ -76,8 +79,10 @@ class PROTOBUF_EXPORT GzipInputStream : public ZeroCopyInputStream {
    virtual ~GzipInputStream();
  
    // Return last error message or NULL if no error.
@@ -104,30 +65,29 @@ index b1ce1d36c..d5d560ea7 100644
  
    // implements ZeroCopyInputStream ----------------------------------
    bool Next(const void** data, int* size);
-@@ -90,8 +94,10 @@ class PROTOBUF_EXPORT GzipInputStream : public ZeroCopyInputStream {
+@@ -90,8 +95,10 @@ class PROTOBUF_EXPORT GzipInputStream : public ZeroCopyInputStream {
  
    ZeroCopyInputStream* sub_stream_;
  
-+ #if HAVE_ZLIB
++#if HAVE_ZLIB
    z_stream zcontext_;
    int zerror_;
-+ #endif // HAVE_ZLIB
++#endif // HAVE_ZLIB
  
    void* output_buffer_;
    void* output_position_;
-@@ -142,9 +148,11 @@ class PROTOBUF_EXPORT GzipOutputStream : public ZeroCopyOutputStream {
+@@ -143,8 +150,10 @@ class PROTOBUF_EXPORT GzipOutputStream : public ZeroCopyOutputStream {
-
    virtual ~GzipOutputStream();
  
-+#if HAVE_ZLIB
    // Return last error message or NULL if no error.
++#if HAVE_ZLIB
    inline const char* ZlibErrorMessage() const { return zcontext_.msg; }
    inline int ZlibErrorCode() const { return zerror_; }
 +#endif  // HAVE_ZLIB
  
    // Flushes data written so far to zipped data in the underlying stream.
    // It is the caller's responsibility to flush the underlying stream if
-@@ -177,8 +185,10 @@ class PROTOBUF_EXPORT GzipOutputStream : public ZeroCopyOutputStream {
+@@ -177,8 +186,10 @@ class PROTOBUF_EXPORT GzipOutputStream : public ZeroCopyOutputStream {
    void* sub_data_;
    int sub_data_size_;