Refactor protobuf flag abstraction layer to custom flag targets

bazel/flags/BUILD

@@ -1,5 +1,6 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
-load("@bazel_skylib//rules:common_settings.bzl", "bool_flag", "string_flag", "string_list_flag")
+load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
+load("//bazel/private:compat_flag.bzl", "compat_bool_flag", "compat_string_list_flag")
 
 package(
     default_applicable_licenses = ["//:license"],
@@ -25,9 +26,10 @@ filegroup(
     ],
 )
 
-bool_flag(
+compat_bool_flag(
     name = "experimental_proto_descriptor_sets_include_source_info",
     build_setting_default = False,
+    native_flag = "experimental_proto_descriptor_sets_include_source_info",
     scope = "universal",
 )
 
@@ -36,9 +38,10 @@ label_flag(
     build_setting_default = "@bazel_tools//tools/proto:protoc",
 )
 
-string_list_flag(
+compat_string_list_flag(
     name = "protocopt",
     build_setting_default = [],
+    fragment_field = "experimental_protoc_opts",
     scope = "universal",
 )
 
@@ -75,39 +78,45 @@ config_setting(
 )
 
 # TODO: deprecate this flag.
-string_flag(
+compat_bool_flag(
     name = "strict_proto_deps",
-    build_setting_default = "error",
+    build_setting_default = True,
+    native_flag = "strict_proto_deps",
     scope = "universal",
-    values = [
-        "off",
-        "OFF",
-        "warn",
-        "WARN",
-        "error",
-        "ERROR",
-        "strict",
-        "STRICT",
-        "default",
-        "DEFAULT",
-    ],
+    values = {
+        False: [
+            "off",
+            "OFF",
+        ],
+        True: [
+            "warn",
+            "WARN",
+            "error",
+            "ERROR",
+            "strict",
+            "STRICT",
+        ],
+    },
 )
 
 # TODO: deprecate this flag.
-string_flag(
+compat_bool_flag(
     name = "strict_public_imports",
-    build_setting_default = "off",
+    build_setting_default = False,
+    native_flag = "strict_public_imports",
     scope = "universal",
-    values = [
-        "off",
-        "OFF",
-        "warn",
-        "WARN",
-        "error",
-        "ERROR",
-        "strict",
-        "STRICT",
-        "default",
-        "DEFAULT",
-    ],
+    values = {
+        False: [
+            "off",
+            "OFF",
+        ],
+        True: [
+            "warn",
+            "WARN",
+            "error",
+            "ERROR",
+            "strict",
+            "STRICT",
+        ],
+    },
 )

bazel/flags/cc/BUILD

@@ -1,5 +1,6 @@
-load("@bazel_skylib//rules:common_settings.bzl", "bool_flag", "string_list_flag")
+load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
 load("@rules_shell//shell:sh_binary.bzl", "sh_binary")
+load("//bazel/private:compat_flag.bzl", "compat_string_list_flag")
 
 package(
     default_applicable_licenses = ["//:license"],
@@ -19,14 +20,16 @@ alias(
     deprecation = "Use //bazel/flags:protocopt instead.",
 )
 
-string_list_flag(
+compat_string_list_flag(
     name = "cc_proto_library_header_suffixes",
     build_setting_default = [".pb.h"],
+    fragment_field = "cc_proto_library_header_suffixes",
     scope = "universal",
 )
 
-string_list_flag(
+compat_string_list_flag(
     name = "cc_proto_library_source_suffixes",
     build_setting_default = [".pb.cc"],
+    fragment_field = "cc_proto_library_source_suffixes",
     scope = "universal",
 )

bazel/flags/flags.bzl

@@ -8,75 +8,22 @@ visibility([
     "//third_party/grpc/bazel",
 ])
 
-# Maps flag names to their native reference
-_FLAGS = {
-    "protocopt": struct(
-        native = lambda ctx: getattr(ctx.fragments.proto, "experimental_protoc_opts"),
-        default = [],
-    ),
-    "experimental_proto_descriptor_sets_include_source_info": struct(
-        native = lambda ctx: getattr(ctx.attr, "_experimental_proto_descriptor_sets_include_source_info_native")[BuildSettingInfo].value,
-        default = False,
-    ),
-    "proto_compiler": struct(native = lambda ctx: getattr(ctx.attr, "_proto_compiler_native")[BuildSettingInfo].value, default = "@bazel_tools//tools/proto:protoc"),
-    "strict_proto_deps": struct(
-        native = lambda ctx: getattr(ctx.attr, "_strict_proto_deps_native")[BuildSettingInfo].value,
-        default = "error",
-    ),
-    "strict_public_imports": struct(
-        native = lambda ctx: getattr(ctx.attr, "_strict_public_imports_native")[BuildSettingInfo].value,
-        default = "off",
-    ),
-    "cc_proto_library_header_suffixes": struct(
-        native = lambda ctx: getattr(ctx.fragments.proto, "cc_proto_library_header_suffixes"),
-        default = [".pb.h"],
-    ),
-    "cc_proto_library_source_suffixes": struct(
-        native = lambda ctx: getattr(ctx.fragments.proto, "cc_proto_library_source_suffixes"),
-        default = [".pb.cc"],
-    ),
-    "proto_toolchain_for_java": struct(
-        native = lambda ctx: "//:java_toolchain",
-        default = "//:java_toolchain",
-    ),
-    "proto_toolchain_for_javalite": struct(
-        native = lambda ctx: "//:javalite_toolchain",
-        default = "//:javalite_toolchain",
-    ),
-    "proto_toolchain_for_cc": struct(
-        native = lambda ctx: "//:cc_toolchain",
-        default = "//:cc_toolchain",
-    ),
-}
-
 def get_flag_value(ctx, flag_name):
-    """Returns the value of the given flag in Starlark if it's set, otherwise reads the Java flag value, if the proto fragment exists.
+    """Returns the value of the given flag attribute from rule context.
 
     Args:
         ctx: The rule context.
         flag_name: The name of the flag to get the value for.
 
     Returns:
-        The value of the flag.
+        The value of the flag. If the value is a list, returns a mutable copy.
     """
-
-    # We probably got here from toolchains.find_toolchain. Leave the attribute alone.
-    if flag_name not in _FLAGS:
-        return getattr(ctx.attr, "_" + flag_name)
-
-    starlark_flag = getattr(ctx.attr, "_" + flag_name)
-
-    # Label flags don't have a BuildSettingInfo, just get the value.
-    if "toolchain" in flag_name:
-        starlark_flag_is_set = starlark_flag.label != _FLAGS[flag_name].default
-        starlark_value = starlark_flag
-    else:
-        starlark_flag_is_set = starlark_flag[BuildSettingInfo].value != _FLAGS[flag_name].default
-        starlark_value = starlark_flag[BuildSettingInfo].value
-
-    # Starlark flags take precedence over native flags.
-    # Also of course, use the Starlark value if the proto fragment no longer exists.
-    if starlark_flag_is_set or not hasattr(ctx.fragments, "proto"):
-        return starlark_value
-    else:
-        return _FLAGS[flag_name].native(ctx)
+    attr_val = getattr(ctx.attr, "_" + flag_name)
+    if BuildSettingInfo in attr_val:
+        val = attr_val[BuildSettingInfo].value
+        if type(val) == "list":
+            return list(val)
+        return val
+    if type(attr_val) == "list":
+        return list(attr_val)
+    return attr_val

bazel/private/BUILD

@@ -1,5 +1,4 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
-load(":native_bool_flag.bzl", "native_bool_flag")
 
 package(default_applicable_licenses = ["//:license"])
 
@@ -168,32 +167,9 @@ bzl_library(
     ],
 )
 
-native_bool_flag(
-    name = "experimental_proto_descriptor_sets_include_source_info",
-    flag = "experimental_proto_descriptor_sets_include_source_info",
-    match_value = "true",
-    visibility = ["//bazel:__subpackages__"],
-)
-
-native_bool_flag(
-    name = "strict_proto_deps",
-    flag = "strict_proto_deps",
-    match_value = "off",
-    result = False,
-    visibility = ["//bazel:__subpackages__"],
-)
-
-native_bool_flag(
-    name = "strict_public_imports",
-    flag = "strict_public_imports",
-    match_value = "off",
-    result = False,
-    visibility = ["//bazel:__subpackages__"],
-)
-
 bzl_library(
-    name = "native_bool_flag_bzl",
-    srcs = ["native_bool_flag.bzl"],
+    name = "compat_flag_bzl",
+    srcs = ["compat_flag.bzl"],
     visibility = ["//visibility:private"],
     deps = ["@bazel_skylib//rules:common_settings"],
 )
@@ -203,8 +179,8 @@ filegroup(
     testonly = True,
     srcs = [
         "BUILD",
+        ":compat_flag_bzl",
         ":java_proto_library_bzl",
-        ":native_bool_flag_bzl",
         ":toolchain_helpers_bzl",
         "//bazel:for_bazel_tests",
         "//bazel/private/oss/toolchains:for_bazel_tests",