Add a Starlark flag to select() on to get the Python mode
This adds @bazel_tools//tools/python:python_version, whose value is always either "PY2" or "PY3" (never undefined), and which works regardless of the value of --experimental_better_python_version_mixing. Users who need to select() on the Python version should use this label in their `config_setting`s. Users should not select() on "force_python" or "python_version" because these flags may not always represent the true Python version state, and can lead to action conflict errors.
Work toward #6583.
RELNOTES: None
PiperOrigin-RevId: 226235967
diff --git a/src/test/shell/integration/python_test.sh b/src/test/shell/integration/python_test.sh
index 23c961e..1da34ef 100755
--- a/src/test/shell/integration/python_test.sh
+++ b/src/test/shell/integration/python_test.sh
@@ -183,4 +183,60 @@
expect_log "I am Python 3"
}
+# Helper function for test_select_on_python_version. Dependent on its setup.
+function do_test_select_on_python_version() {
+ flags="$1"
+ result="$2"
+ bazel run //test:main $flags \
+ &> $TEST_log || fail "bazel run failed"
+ expect_log "I am $result" "Expected version $result for flags \"$flags\""
+}
+
+function test_select_on_python_version() {
+ mkdir -p test
+
+ cat > test/BUILD << EOF
+sh_binary(name = "main",
+ srcs = select({
+ "$TOOLS_REPOSITORY//tools/python:PY2": ["py2.sh"],
+ "$TOOLS_REPOSITORY//tools/python:PY3": ["py3.sh"],
+ }),
+)
+EOF
+
+ cat > test/py2.sh << EOF
+#/bin/sh
+
+echo "I am PY2"
+EOF
+ sed s/PY2/PY3/ test/py2.sh > test/py3.sh
+ chmod u+x test/py2.sh test/py3.sh
+
+ DEFAULT_VERSION=PY2
+
+ EXPFLAG="--experimental_better_python_version_mixing=true"
+ NO_EXPFLAG="--experimental_better_python_version_mixing=false"
+
+ # --force_python and --python_version have three possible values (including
+ # not being set at all). The experimental flag has two possible values, but
+ # when it's disabled --python_version may not be set. So that's 12
+ # combinations to enumerate here.
+
+ do_test_select_on_python_version "$NO_EXPFLAG" "$DEFAULT_VERSION"
+ do_test_select_on_python_version "$NO_EXPFLAG --force_python=PY2" "PY2"
+ do_test_select_on_python_version "$NO_EXPFLAG --force_python=PY3" "PY3"
+
+ do_test_select_on_python_version "$EXPFLAG" "$DEFAULT_VERSION"
+ do_test_select_on_python_version "$EXPFLAG --force_python=PY2" "PY2"
+ do_test_select_on_python_version "$EXPFLAG --force_python=PY3" "PY3"
+
+ do_test_select_on_python_version "$EXPFLAG --python_version=PY2" "PY2"
+ do_test_select_on_python_version "$EXPFLAG --force_python=PY2 --python_version=PY2" "PY2"
+ do_test_select_on_python_version "$EXPFLAG --force_python=PY3 --python_version=PY2" "PY2"
+
+ do_test_select_on_python_version "$EXPFLAG --python_version=PY3" "PY3"
+ do_test_select_on_python_version "$EXPFLAG --force_python=PY2 --python_version=PY3" "PY3"
+ do_test_select_on_python_version "$EXPFLAG --force_python=PY3 --python_version=PY3" "PY3"
+}
+
run_suite "Tests for the Python rules"
diff --git a/tools/python/BUILD b/tools/python/BUILD
index a344b44..62c1b80 100644
--- a/tools/python/BUILD
+++ b/tools/python/BUILD
@@ -1,3 +1,5 @@
+load(":python_version.bzl", "define_python_version_flag")
+
package(default_visibility = ["//visibility:public"])
sh_binary(
@@ -6,27 +8,15 @@
)
filegroup(
- name = "srcs_and_embedded_tools",
- srcs = [
- # Tools are build from the workspace for tests.
- "2to3.sh",
- "BUILD",
- ],
- visibility = ["//visibility:private"],
-)
-
-filegroup(
name = "srcs",
- srcs = [
- ":srcs_and_embedded_tools",
+ srcs = glob(["**"]) + [
"//tools/python/runfiles:srcs",
],
)
filegroup(
name = "embedded_tools",
- srcs = [
- ":srcs_and_embedded_tools",
+ srcs = glob(["**"]) + [
"//tools/python/runfiles:embedded_tools",
],
visibility = ["//tools:__pkg__"],
@@ -39,3 +29,48 @@
],
visibility = ["//tools:__pkg__"],
)
+
+# This target can be used to inspect the current Python major version. To use,
+# put it in the `flag_values` attribute of a `config_setting` and test it
+# against the values "PY2" or "PY3". It will always match one or the other.
+#
+# If you do not need to test any other flags in combination with the Python
+# version, then as a convenience you may use the predefined `config_setting`s
+# `@bazel_tools//python:PY2` and `@bazel_tools//python:PY3`.
+#
+# Example usage:
+#
+# config_setting(
+# name = "py3_on_arm",
+# values = {"cpu": "arm"},
+# flag_values = {"@bazel_tools//python:python_version": "PY3"},
+# )
+#
+# my_target(
+# ...
+# some_attr = select({
+# ":py3_on_arm": ...,
+# ...
+# }),
+# ...
+# )
+#
+# Caution: Do not `select()` on the built-in command-line flags `--force_python`
+# or `--python_version`, as they do not always reflect the true Python version
+# of the current target. `select()`-ing on them can lead to action conflicts and
+# will be disallowed.
+define_python_version_flag(
+ name = "python_version",
+)
+
+config_setting(
+ name = "PY2",
+ flag_values = {":python_version": "PY2"},
+ visibility = ["//visibility:public"],
+)
+
+config_setting(
+ name = "PY3",
+ flag_values = {":python_version": "PY3"},
+ visibility = ["//visibility:public"],
+)
diff --git a/tools/python/python_version.bzl b/tools/python/python_version.bzl
new file mode 100644
index 0000000..ef72015
--- /dev/null
+++ b/tools/python/python_version.bzl
@@ -0,0 +1,126 @@
+# 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"
+
+# Keep in sync with default value of --experimental_better_python_version_mixing.
+_DEFAULT_EXPERIMENTAL_FLAG = False
+
+# Keep in sync with PythonVersion.DEFAULT_TARGET_VALUE.
+_DEFAULT_PYTHON_VERSION = "PY2"
+
+def _python_version_flag_impl(ctx):
+ # Convert the string-encoded tri-value to a boolean, where unset yields the
+ # default value.
+ experimental = {
+ _TRUE: True,
+ _FALSE: False,
+ _UNSET: _DEFAULT_EXPERIMENTAL_FLAG,
+ }[ctx.attr.experimental_flag]
+
+ # Version is determined using the same logic as in PythonOptions#getPythonVersion:
+ # 1. Under the experimental flag, consult --python_version first,
+ # otherwise ignore it.
+ # 2. Next fall back on --force_python.
+ # 3. Final fallback is on the hardcoded default.
+ if experimental and ctx.attr.python_version_flag != _UNSET:
+ version = ctx.attr.python_version_flag
+ elif ctx.attr.force_python_flag != _UNSET:
+ version = ctx.attr.force_python_flag
+ else:
+ version = _DEFAULT_PYTHON_VERSION
+
+ 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 = {
+ "experimental_flag": attr.string(mandatory = True, values = [_TRUE, _FALSE, _UNSET]),
+ "force_python_flag": attr.string(mandatory = True, values = [_PY2, _PY3, _UNSET]),
+ "python_version_flag": attr.string(mandatory = True, values = [_PY2, _PY3, _UNSET]),
+ },
+)
+
+def define_python_version_flag(name):
+ """Defines the target to expose the Python version to select().
+
+ For use only by @bazel_tools//python:BUILD; see the documentation comment
+ there.
+
+ Args:
+ name: The name of the target to introduce.
+ """
+
+ # Config settings for the underlying native flags we depend on:
+ # --experimental_better_python_version_mixing, --force_python, and
+ # --python_version.
+ native.config_setting(
+ name = "_experimental_false",
+ values = {"experimental_better_python_version_mixing": "false"},
+ visibility = ["//visibility:private"],
+ )
+ native.config_setting(
+ name = "_experimental_true",
+ values = {"experimental_better_python_version_mixing": "true"},
+ visibility = ["//visibility:private"],
+ )
+ native.config_setting(
+ name = "_force_python_setting_PY2",
+ values = {"force_python": "PY2"},
+ visibility = ["//visibility:private"],
+ )
+ native.config_setting(
+ name = "_force_python_setting_PY3",
+ values = {"force_python": "PY3"},
+ visibility = ["//visibility:private"],
+ )
+ 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"],
+ )
+
+ _python_version_flag(
+ name = name,
+ experimental_flag = select({
+ ":_experimental_false": _FALSE,
+ ":_experimental_true": _TRUE,
+ "//conditions:default": _UNSET,
+ }),
+ force_python_flag = select({
+ ":_force_python_setting_PY2": _PY2,
+ ":_force_python_setting_PY3": _PY3,
+ "//conditions:default": _UNSET,
+ }),
+ python_version_flag = select({
+ ":_python_version_setting_PY2": _PY2,
+ ":_python_version_setting_PY3": _PY3,
+ "//conditions:default": _UNSET,
+ }),
+ visibility = ["//visibility:public"],
+ )
diff --git a/tools/python/runfiles/BUILD b/tools/python/runfiles/BUILD
index 08cec71..8ef28b3 100644
--- a/tools/python/runfiles/BUILD
+++ b/tools/python/runfiles/BUILD
@@ -2,13 +2,7 @@
filegroup(
name = "srcs",
- srcs = glob(
- ["**"],
- exclude = [
- ".*",
- "*~",
- ],
- ),
+ srcs = glob(["**"]),
visibility = ["//tools/python:__pkg__"],
)
