Add internal macros and partially migrate Bazel for upcoming change

This adds `@bazel_tools//tools/python:private/defs.bzl`, which defines macro wrappers around the four native Python rules (`py_library`, `py_binary`, `py_test`, `py_runtime`). These wrappers simulate the behavior of `@rules_python//python:defs.bzl`, so that they are compatible with the upcoming `--incompatible_load_python_rules_from_bzl` flag.

This change also updates many direct uses of the native Python rules to use the wrappers instead. However, changes to the third_party/ directory have to be in a separate commit.

The new macros should only be used by Bazel itself. All external users should use @rules_python instead.

I'm omitting updating src/test/py/bazel/testdata/runfiles_test/*/BUILD.mock files because they appear to be tests that shouldn't complain until the flag is flipped, and I'm not sure that adding a load won't break them. Also not updating the examples/ dir for similar reasons.

Work toward #9006.

RELNOTES: None
PiperOrigin-RevId: 260858287

BUILD

@@ -1,5 +1,7 @@
 # Bazel - Google's Build System
 
+load("//tools/python:private/defs.bzl", "py_binary")
+
 package(default_visibility = ["//scripts/release:__pkg__"])
 
 exports_files(["LICENSE"])

scripts/docs/BUILD

@@ -1,3 +1,5 @@
+load("//tools/python:private/defs.bzl", "py_library", "py_binary")
+
 filegroup(
     name = "srcs",
     srcs = glob(["**"]),

src/BUILD

@@ -1,5 +1,6 @@
 # Packaging
 
+load("//tools/python:private/defs.bzl", "py_library", "py_binary")
 load(":embedded_tools.bzl", "srcsfile")
 load(":rule_size_test.bzl", "rule_size_test")
 

src/test/java/com/google/devtools/build/lib/packages/util/BazelMockPythonSupport.java

@@ -34,6 +34,7 @@ public void setup(MockToolsConfig config) throws IOException {
     addTool(config, "tools/python/srcs_version.bzl");
     addTool(config, "tools/python/toolchain.bzl");
     addTool(config, "tools/python/utils.bzl");
+    addTool(config, "tools/python/private/defs.bzl");
 
     config.create(
         TestConstants.TOOLS_REPOSITORY_SCRATCH + "tools/python/BUILD",

src/test/py/bazel/BUILD

@@ -1,6 +1,7 @@
 package(default_visibility = ["//visibility:private"])
 
 load("@rules_cc//cc:defs.bzl", "cc_binary")
+load("//tools/python:private/defs.bzl", "py_library", "py_test")
 
 filegroup(
     name = "srcs",

src/test/starlark/BUILD

@@ -3,6 +3,7 @@ load(
     "rule_test",
     "file_test",
 )
+load("//tools/python:private/defs.bzl", "py_test")
 
 package(default_visibility = ["//src:__subpackages__"])
 

tools/android/BUILD

@@ -1,3 +1,5 @@
+load("//tools/python:private/defs.bzl", "py_library", "py_binary", "py_test")
+
 package(default_visibility = ["//tools:__pkg__"])
 
 py_binary(

tools/android/BUILD.tools

@@ -1,3 +1,5 @@
+load("//tools/python:private/defs.bzl", "py_library", "py_binary")
+
 package(default_visibility = ["//visibility:public"])
 
 alias(

tools/aquery_differ/BUILD

@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+load("//tools/python:private/defs.bzl", "py_library", "py_binary", "py_test")
+
 package(default_visibility = ["//visibility:public"])
 
 licenses(["notice"])  # Apache 2.0

tools/build_defs/hash/BUILD

@@ -1,3 +1,5 @@
+load("//tools/python:private/defs.bzl", "py_binary")
+
 licenses(["notice"])  # Apache 2.0
 
 filegroup(

tools/build_defs/pkg/BUILD

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 load("//tools/config:common_settings.bzl", "bool_flag")
+load("//tools/python:private/defs.bzl", "py_library", "py_binary", "py_test")
 
 licenses(["notice"])  # Apache 2.0
 

tools/build_rules/BUILD

@@ -1,3 +1,5 @@
+load("//tools/python:private/defs.bzl", "py_test")
+
 licenses(["notice"])  # Apache 2.0
 
 filegroup(

tools/jdk/BUILD

@@ -19,6 +19,7 @@ load(
     "remote_java_tools_java_import",
 )
 load("@rules_cc//cc:defs.bzl", "cc_binary")
+load("//tools/python:private/defs.bzl", "py_binary", "py_test")
 
 package(default_visibility = ["//visibility:public"])
 

tools/python/BUILD

@@ -1,3 +1,4 @@
+load("//tools/python:private/defs.bzl", "py_test")
 load(":utils.bzl", "expand_pyversion_template")
 
 package(default_visibility = ["//visibility:public"])

tools/python/BUILD.tools

@@ -40,6 +40,7 @@ exports_files([
     "srcs_version.bzl",
     "toolchain.bzl",
     "utils.bzl",
+    "private/defs.bzl",
     # write_file.bzl fortunately doesn't need to be exposed because it's only
     # used in this BUILD file.
 ])

tools/python/private/defs.bzl

@@ -0,0 +1,43 @@
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""This is a Bazel-internal file; do not load() it!
+
+This file replicates the behavior of the macros in bazelbuild/rules_python's
+`//python:defs.bzl` file, allowing the four native rules to be used even with
+`--incompatible_load_python_rules_from_bzl` enabled.
+
+We need this file because Bazel's own codebase may not depend on rules_python.
+"""
+
+_MIGRATION_TAG = "__PYTHON_RULES_MIGRATION_DO_NOT_USE_WILL_BREAK__"
+
+def _add_tags(attrs):
+    if "tags" in attrs and attrs["tags"] != None:
+        attrs["tags"] += [_MIGRATION_TAG]
+    else:
+        attrs["tags"] = [_MIGRATION_TAG]
+    return attrs
+
+def py_library(**attrs):
+    native.py_library(**_add_tags(attrs))
+
+def py_binary(**attrs):
+    native.py_binary(**_add_tags(attrs))
+
+def py_test(**attrs):
+    native.py_test(**_add_tags(attrs))
+
+def py_runtime(**attrs):
+    native.py_runtime(**_add_tags(attrs))

tools/python/runfiles/BUILD

@@ -1,3 +1,5 @@
+load("//tools/python:private/defs.bzl", "py_library", "py_test")
+
 package(default_visibility = ["//visibility:private"])
 
 filegroup(

tools/python/runfiles/BUILD.tools

@@ -1,3 +1,5 @@
+load("//tools/python:private/defs.bzl", "py_library")
+
 py_library(
     name = "runfiles",
     srcs = ["runfiles.py"],

tools/python/toolchain.bzl

@@ -15,6 +15,7 @@
 """Definitions related to the Python toolchain."""
 
 load(":utils.bzl", "expand_pyversion_template")
+load(":private/defs.bzl", "py_runtime")
 
 def _py_runtime_pair_impl(ctx):
     if ctx.attr.py2_runtime != None:
@@ -159,28 +160,28 @@ def define_autodetecting_toolchain(
     # have to use a workaround to allow it to be depended on by py_runtime. See
     # https://github.com/bazelbuild/bazel/issues/4286#issuecomment-475661317.
 
-    native.py_runtime(
+    py_runtime(
         name = "_autodetecting_py2_runtime",
         interpreter = ":py2wrapper.sh",
         python_version = "PY2",
         visibility = ["//visibility:private"],
     )
 
-    native.py_runtime(
+    py_runtime(
         name = "_autodetecting_py3_runtime",
         interpreter = ":py3wrapper.sh",
         python_version = "PY3",
         visibility = ["//visibility:private"],
     )
 
-    native.py_runtime(
+    py_runtime(
         name = "_autodetecting_py2_runtime_nonstrict",
         interpreter = ":py2wrapper_nonstrict.sh",
         python_version = "PY2",
         visibility = ["//visibility:private"],
     )
 
-    native.py_runtime(
+    py_runtime(
         name = "_autodetecting_py3_runtime_nonstrict",
         interpreter = ":py3wrapper_nonstrict.sh",
         python_version = "PY3",
@@ -190,7 +191,7 @@ def define_autodetecting_toolchain(
     # This is a dummy runtime whose interpreter_path triggers the native rule
     # logic to use the legacy behavior on Windows.
     # TODO(#7844): Remove this target.
-    native.py_runtime(
+    py_runtime(
         name = "_sentinel_py2_runtime",
         interpreter_path = "/_magic_pyruntime_sentinel_do_not_use",
         python_version = "PY2",