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internal(pystar): Copy @bazel_tools//tools/python files to rules_python (bazel-contrib#1437)
This copies the useful pieces from @bazel_tools//tools/python into rules_python. They're copied in relatively as-is, and not yet used. Subsequent commits will make them usable. These pieces are: * Bootstrap template (python_bootstrap_template.txt) * The py_runtime_pair rule (split from toolchain.bzl) * Autodetecting toolchain setup (split from toolchain.bzl) Work towards bazel-contrib#1069
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‎python/private/autodetecting_toolchain.bzl

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# Copyright 2019 The Bazel Authors. All rights reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Definitions related to the Python toolchain."""
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load(":utils.bzl", "expand_pyversion_template")
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def define_autodetecting_toolchain(
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name,
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pywrapper_template,
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windows_config_setting):
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"""Defines the autodetecting Python toolchain.
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This includes both strict and non-strict variants.
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For use only by @bazel_tools//tools/python:BUILD; see the documentation
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comment there.
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Args:
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name: The name of the toolchain to introduce. Must have value
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"autodetecting_toolchain". This param is present only to make the
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BUILD file more readable.
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pywrapper_template: The label of the pywrapper_template.txt file.
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windows_config_setting: The label of a config_setting that matches when
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the platform is windows, in which case the toolchain is configured
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in a way that triggers a workaround for #7844.
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"""
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if native.package_name() != "tools/python":
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fail("define_autodetecting_toolchain() is private to " +
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"@bazel_tools//tools/python")
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if name != "autodetecting_toolchain":
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fail("Python autodetecting toolchain must be named " +
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"'autodetecting_toolchain'")
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expand_pyversion_template(
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name = "_generate_wrappers",
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template = pywrapper_template,
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out2 = ":py2wrapper.sh",
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out3 = ":py3wrapper.sh",
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out2_nonstrict = ":py2wrapper_nonstrict.sh",
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out3_nonstrict = ":py3wrapper_nonstrict.sh",
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visibility = ["//visibility:private"],
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)
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# Note that the pywrapper script is a .sh file, not a sh_binary target. If
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# we needed to make it a proper shell target, e.g. because it needed to
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# access runfiles and needed to depend on the runfiles library, then we'd
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# have to use a workaround to allow it to be depended on by py_runtime. See
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# https://github.com/bazelbuild/bazel/issues/4286#issuecomment-475661317.
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# buildifier: disable=native-py
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py_runtime(
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name = "_autodetecting_py3_runtime",
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interpreter = ":py3wrapper.sh",
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python_version = "PY3",
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stub_shebang = "#!/usr/bin/env python3",
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visibility = ["//visibility:private"],
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)
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# buildifier: disable=native-py
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py_runtime(
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name = "_autodetecting_py3_runtime_nonstrict",
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interpreter = ":py3wrapper_nonstrict.sh",
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python_version = "PY3",
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stub_shebang = "#!/usr/bin/env python3",
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visibility = ["//visibility:private"],
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)
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# This is a dummy runtime whose interpreter_path triggers the native rule
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# logic to use the legacy behavior on Windows.
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# TODO(#7844): Remove this target.
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# buildifier: disable=native-py
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py_runtime(
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name = "_magic_sentinel_runtime",
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interpreter_path = "/_magic_pyruntime_sentinel_do_not_use",
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python_version = "PY3",
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visibility = ["//visibility:private"],
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)
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py_runtime_pair(
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name = "_autodetecting_py_runtime_pair",
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py3_runtime = select({
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# If we're on windows, inject the sentinel to tell native rule logic
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# that we attempted to use the autodetecting toolchain and need to
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# switch back to legacy behavior.
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# TODO(#7844): Remove this hack.
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windows_config_setting: ":_magic_sentinel_runtime",
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"//conditions:default": ":_autodetecting_py3_runtime",
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}),
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visibility = ["//visibility:public"],
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)
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py_runtime_pair(
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name = "_autodetecting_py_runtime_pair_nonstrict",
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py3_runtime = select({
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# Same hack as above.
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# TODO(#7844): Remove this hack.
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windows_config_setting: ":_magic_sentinel_runtime",
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"//conditions:default": ":_autodetecting_py3_runtime_nonstrict",
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}),
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visibility = ["//visibility:public"],
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)
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native.toolchain(
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name = name,
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toolchain = ":_autodetecting_py_runtime_pair",
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toolchain_type = ":toolchain_type",
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visibility = ["//visibility:public"],
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)
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native.toolchain(
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name = name + "_nonstrict",
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toolchain = ":_autodetecting_py_runtime_pair_nonstrict",
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toolchain_type = ":toolchain_type",
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visibility = ["//visibility:public"],
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)

‎python/private/py_runtime_pair.bzl

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# Copyright 2019 The Bazel Authors. All rights reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Implementation of py_runtime_pair."""
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# TODO: move py_runtime_pair into rules_python (and the rest of @bazel_tools//python)
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# py_runtime should be loaded from rules_python, but this creates a circular dep, because py_runtime_pair is imported there.
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py_runtime = native.py_runtime
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def _py_runtime_pair_impl(ctx):
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if ctx.attr.py2_runtime != None:
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py2_runtime = ctx.attr.py2_runtime[PyRuntimeInfo]
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if py2_runtime.python_version != "PY2":
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fail("The Python runtime in the 'py2_runtime' attribute did not have " +
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"version 'PY2'")
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else:
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py2_runtime = None
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if ctx.attr.py3_runtime != None:
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py3_runtime = ctx.attr.py3_runtime[PyRuntimeInfo]
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if py3_runtime.python_version != "PY3":
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fail("The Python runtime in the 'py3_runtime' attribute did not have " +
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"version 'PY3'")
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else:
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py3_runtime = None
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# TODO: Uncomment this after --incompatible_python_disable_py2 defaults to true
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# if _is_py2_disabled(ctx) and py2_runtime != None:
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# fail("Using Python 2 is not supported and disabled; see " +
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# "https://github.com/bazelbuild/bazel/issues/15684")
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return [platform_common.ToolchainInfo(
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py2_runtime = py2_runtime,
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py3_runtime = py3_runtime,
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)]
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# buildifier: disable=unused-variable
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def _is_py2_disabled(ctx):
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# In Google, this file isn't bundled with Bazel, so we have to conditionally
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# check for this flag.
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# TODO: Remove this once a build with the flag is released in Google
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if not hasattr(ctx.fragments.py, "disable_py"):
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return False
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return ctx.fragments.py.disable_py2
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py_runtime_pair = rule(
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implementation = _py_runtime_pair_impl,
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attrs = {
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# The two runtimes are used by the py_binary at runtime, and so need to
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# be built for the target platform.
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"py2_runtime": attr.label(
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providers = [PyRuntimeInfo],
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cfg = "target",
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doc = """\
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The runtime to use for Python 2 targets. Must have `python_version` set to
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`PY2`.
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""",
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),
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"py3_runtime": attr.label(
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providers = [PyRuntimeInfo],
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cfg = "target",
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doc = """\
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The runtime to use for Python 3 targets. Must have `python_version` set to
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`PY3`.
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""",
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),
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},
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fragments = ["py"],
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doc = """\
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A toolchain rule for Python.
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This wraps up to two Python runtimes, one for Python 2 and one for Python 3.
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The rule consuming this toolchain will choose which runtime is appropriate.
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Either runtime may be omitted, in which case the resulting toolchain will be
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unusable for building Python code using that version.
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Usually the wrapped runtimes are declared using the `py_runtime` rule, but any
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rule returning a `PyRuntimeInfo` provider may be used.
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This rule returns a `platform_common.ToolchainInfo` provider with the following
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schema:
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```python
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platform_common.ToolchainInfo(
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py2_runtime = <PyRuntimeInfo or None>,
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py3_runtime = <PyRuntimeInfo or None>,
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)
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```
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Example usage:
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```python
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# In your BUILD file...
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load("@rules_python//python:defs.bzl", "py_runtime_pair")
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py_runtime(
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name = "my_py2_runtime",
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interpreter_path = "/system/python2",
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python_version = "PY2",
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)
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py_runtime(
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name = "my_py3_runtime",
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interpreter_path = "/system/python3",
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python_version = "PY3",
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)
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py_runtime_pair(
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name = "my_py_runtime_pair",
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py2_runtime = ":my_py2_runtime",
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py3_runtime = ":my_py3_runtime",
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)
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toolchain(
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name = "my_toolchain",
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target_compatible_with = <...>,
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toolchain = ":my_py_runtime_pair",
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toolchain_type = "@rules_python//python:toolchain_type",
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)
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```
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```python
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# In your WORKSPACE...
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register_toolchains("//my_pkg:my_toolchain")
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```
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""",
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)

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