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# Copyright 2018 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.
"""Utilities for selecting the Python major version (Python 2 vs Python 3)."""
_UNSET = "UNSET"
_FALSE = "FALSE"
_TRUE = "TRUE"
_PY2 = "PY2"
_PY3 = "PY3"
def _python_version_flag_impl(ctx):
# Version is determined using the same logic as in
# PythonOptions#getPythonVersion:
#
# 1. Consult --python_version first, if present.
# 2. Fallback on the default, which is governed by an incompatible change
# flag.
if ctx.attr.python_version_flag != _UNSET:
version = ctx.attr.python_version_flag
else:
version = _PY3 if ctx.attr.incompatible_py3_is_default_flag else _PY2
if version not in ["PY2", "PY3"]:
fail("Internal error: _python_version_flag should only be able to " +
"match 'PY2' or 'PY3'")
return [config_common.FeatureFlagInfo(value = version)]
_python_version_flag = rule(
implementation = _python_version_flag_impl,
attrs = {
"python_version_flag": attr.string(mandatory = True, values = [_PY2, _PY3, _UNSET]),
"incompatible_py3_is_default_flag": attr.bool(mandatory = True),
},
)
def define_python_version_flag(name):
"""Defines the target to expose the Python version to select().
For use only by @bazel_tools//tools/python:BUILD; see the documentation
comment there.
Args:
name: The name of the target to introduce. Must have value
"python_version". This param is present only to make the BUILD file
more readable.
"""
if native.package_name() != "tools/python":
fail("define_python_version_flag() is private to " +
"@bazel_tools//tools/python")
if name != "python_version":
fail("Python version flag must be named 'python_version'")
# Config settings for the underlying native flags we depend on:
# --python_version and --incompatible_py3_is_default.
native.config_setting(
name = "_python_version_setting_PY2",
values = {"python_version": "PY2"},
visibility = ["//visibility:private"],
)
native.config_setting(
name = "_python_version_setting_PY3",
values = {"python_version": "PY3"},
visibility = ["//visibility:private"],
)
native.config_setting(
name = "_incompatible_py3_is_default_setting_false",
values = {"incompatible_py3_is_default": "false"},
visibility = ["//visibility:private"],
)
native.config_setting(
name = "_incompatible_py3_is_default_setting_true",
values = {"incompatible_py3_is_default": "true"},
visibility = ["//visibility:private"],
)
_python_version_flag(
name = name,
python_version_flag = select({
":_python_version_setting_PY2": _PY2,
":_python_version_setting_PY3": _PY3,
"//conditions:default": _UNSET,
}),
incompatible_py3_is_default_flag = select({
":_incompatible_py3_is_default_setting_false": False,
":_incompatible_py3_is_default_setting_true": True,
}),
visibility = ["//visibility:public"],
)
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