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# Copyright 2022 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.
"""Create a repository to hold the toolchains.
This follows guidance here:
https://docs.bazel.build/versions/main/skylark/deploying.html#registering-toolchains
The "complex computation" in our case is simply downloading large artifacts.
This guidance tells us how to avoid that: we put the toolchain targets in the
alias repository with only the toolchain attribute pointing into the
platform-specific repositories.
"""
load(
"//python:versions.bzl",
"PLATFORMS",
"WINDOWS_NAME",
)
load(":repo_utils.bzl", "REPO_DEBUG_ENV_VAR", "repo_utils")
load(":text_util.bzl", "render")
def python_toolchain_build_file_content(
prefix,
python_version,
set_python_version_constraint,
user_repository_name,
loaded_platforms):
"""Creates the content for toolchain definitions for a build file.
Args:
prefix: Python toolchain name prefixes
python_version: Python versions for the toolchains
set_python_version_constraint: string, "True" if the toolchain should
have the Python version constraint added as a requirement for
matching the toolchain, "False" if not.
user_repository_name: names for the user repos
loaded_platforms: {type}`struct` the list of platform structs defining the
loaded platforms. It is as they are defined in `//python:versions.bzl`.
Returns:
build_content: Text containing toolchain definitions
"""
return "\n\n".join([
"""\
py_toolchain_suite(
user_repository_name = "{user_repository_name}_{platform}",
prefix = "{prefix}{platform}",
target_compatible_with = {compatible_with},
flag_values = {flag_values},
python_version = "{python_version}",
set_python_version_constraint = "{set_python_version_constraint}",
)""".format(
compatible_with = render.indent(render.list(meta.compatible_with)).lstrip(),
flag_values = render.indent(render.dict(
meta.flag_values,
key_repr = lambda x: repr(str(x)), # this is to correctly display labels
)).lstrip(),
platform = platform,
set_python_version_constraint = set_python_version_constraint,
user_repository_name = user_repository_name,
prefix = prefix,
python_version = python_version,
)
for platform, meta in loaded_platforms.items()
])
def _toolchains_repo_impl(rctx):
build_content = """\
# Generated by python/private/toolchains_repo.bzl
#
# These can be registered in the workspace file or passed to --extra_toolchains
# flag. By default all these toolchains are registered by the
# python_register_toolchains macro so you don't normally need to interact with
# these targets.
load("@@{rules_python}//python/private:py_toolchain_suite.bzl", "py_toolchain_suite")
""".format(
rules_python = rctx.attr._rules_python_workspace.repo_name,
)
toolchains = python_toolchain_build_file_content(
prefix = "",
python_version = rctx.attr.python_version,
set_python_version_constraint = str(rctx.attr.set_python_version_constraint),
user_repository_name = rctx.attr.user_repository_name,
loaded_platforms = {
k: v
for k, v in PLATFORMS.items()
if k in rctx.attr.platforms
},
)
rctx.file("BUILD.bazel", build_content + toolchains)
toolchains_repo = repository_rule(
_toolchains_repo_impl,
doc = "Creates a repository with toolchain definitions for all known platforms " +
"which can be registered or selected.",
attrs = {
"platforms": attr.string_list(doc = "List of platforms for which the toolchain definitions shall be created"),
"python_version": attr.string(doc = "The Python version."),
"set_python_version_constraint": attr.bool(doc = "if target_compatible_with for the toolchain should set the version constraint"),
"user_repository_name": attr.string(doc = "what the user chose for the base name"),
"_rules_python_workspace": attr.label(default = Label("//:WORKSPACE")),
},
)
def _toolchain_aliases_impl(rctx):
# Base BUILD file for this repository.
build_contents = """\
# Generated by python/private/toolchains_repo.bzl
load("@rules_python//python/private:toolchain_aliases.bzl", "toolchain_aliases")
package(default_visibility = ["//visibility:public"])
exports_files(["defs.bzl"])
PLATFORMS = [
{loaded_platforms}
]
toolchain_aliases(
name = "{py_repository}",
platforms = PLATFORMS,
)
""".format(
py_repository = rctx.attr.user_repository_name,
loaded_platforms = "\n".join([" \"{}\",".format(p) for p in rctx.attr.platforms]),
)
rctx.file("BUILD.bazel", build_contents)
# Expose a Starlark file so rules can know what host platform we used and where to find an interpreter
# when using repository_ctx.path, which doesn't understand aliases.
rctx.file("defs.bzl", content = """\
# Generated by python/private/toolchains_repo.bzl
load("@@{rules_python}//python:pip.bzl", _compile_pip_requirements = "compile_pip_requirements")
load("@@{rules_python}//python/private:deprecation.bzl", "with_deprecation")
load("@@{rules_python}//python/private:text_util.bzl", "render")
load("@@{rules_python}//python:py_binary.bzl", _py_binary = "py_binary")
load("@@{rules_python}//python:py_test.bzl", _py_test = "py_test")
load(
"@@{rules_python}//python/entry_points:py_console_script_binary.bzl",
_py_console_script_binary = "py_console_script_binary",
)
def _with_deprecation(kwargs, *, name):
kwargs["python_version"] = "{python_version}"
return with_deprecation.symbol(
kwargs,
symbol_name = name,
old_load = "@{name}//:defs.bzl",
new_load = "@rules_python//python:{{}}.bzl".format(name),
snippet = render.call(name, **{{k: repr(v) for k,v in kwargs.items()}})
)
def py_binary(**kwargs):
return _py_binary(**_with_deprecation(kwargs, name = "py_binary"))
def py_console_script_binary(**kwargs):
return _py_console_script_binary(**_with_deprecation(kwargs, name = "py_console_script_binary"))
def py_test(**kwargs):
return _py_test(**_with_deprecation(kwargs, name = "py_test"))
def compile_pip_requirements(**kwargs):
return _compile_pip_requirements(**_with_deprecation(kwargs, name = "compile_pip_requirements"))
""".format(
name = rctx.attr.name,
python_version = rctx.attr.python_version,
rules_python = rctx.attr._rules_python_workspace.repo_name,
))
toolchain_aliases = repository_rule(
_toolchain_aliases_impl,
doc = """\
Creates a repository with a shorter name only referencing the python version,
it contains a BUILD.bazel file declaring aliases to the host platform's targets
and is a great fit for any usage related to setting up toolchains for build
actions.""",
attrs = {
"platforms": attr.string_list(
doc = "List of platforms for which aliases shall be created",
),
"python_version": attr.string(doc = "The Python version."),
"user_repository_name": attr.string(
mandatory = True,
doc = "The base name for all created repositories, like 'python38'.",
),
"_rules_python_workspace": attr.label(default = Label("//:WORKSPACE")),
},
environ = [REPO_DEBUG_ENV_VAR],
)
def _host_toolchain_impl(rctx):
rctx.file("BUILD.bazel", """\
# Generated by python/private/toolchains_repo.bzl
exports_files(["python"], visibility = ["//visibility:public"])
""")
os_name = repo_utils.get_platforms_os_name(rctx)
host_platform = _get_host_platform(
rctx = rctx,
logger = repo_utils.logger(rctx),
python_version = rctx.attr.python_version,
os_name = os_name,
cpu_name = repo_utils.get_platforms_cpu_name(rctx),
platforms = rctx.attr.platforms,
)
repo = "@@{py_repository}_{host_platform}".format(
py_repository = rctx.attr.name[:-len("_host")],
host_platform = host_platform,
)
rctx.report_progress("Symlinking interpreter files to the target platform")
host_python_repo = rctx.path(Label("{repo}//:BUILD.bazel".format(repo = repo)))
# The interpreter might not work on platfroms that don't have symlink support if
# we just symlink the interpreter itself. rctx.symlink does a copy in such cases
# so we can just attempt to symlink all of the directories in the host interpreter
# repo, which should be faster than re-downloading it.
for p in host_python_repo.dirname.readdir():
if p.basename in [
# ignore special files created by the repo rule automatically
"BUILD.bazel",
"MODULE.bazel",
"REPO.bazel",
"WORKSPACE",
"WORKSPACE.bazel",
"WORKSPACE.bzlmod",
]:
continue
# symlink works on all platforms that bazel supports, so it should work on
# UNIX and Windows with and without symlink support. For better performance
# users should enable the symlink startup option, however that requires admin
# privileges.
rctx.symlink(p, p.basename)
is_windows = (os_name == WINDOWS_NAME)
python_binary = "python.exe" if is_windows else "python"
# Ensure that we can run the interpreter and check that we are not
# using the host interpreter.
python_tester_contents = """\
from pathlib import Path
import sys
python = Path(sys.executable)
want_python = str(Path("{python}").resolve())
got_python = str(Path(sys.executable).resolve())
assert want_python == got_python, \
"Expected to use a different interpreter:\\nwant: '{{}}'\\n got: '{{}}'".format(
want_python,
got_python,
)
""".format(repo = repo.strip("@"), python = python_binary)
python_tester = rctx.path("python_tester.py")
rctx.file(python_tester, python_tester_contents)
repo_utils.execute_checked(
rctx,
op = "CheckHostInterpreter",
arguments = [rctx.path(python_binary), python_tester],
)
if not rctx.delete(python_tester):
fail("Failed to delete the python tester")
host_toolchain = repository_rule(
_host_toolchain_impl,
doc = """\
Creates a repository with a shorter name meant to be used in the repository_ctx,
which needs to have `symlinks` for the interpreter. This is separate from the
toolchain_aliases repo because referencing the `python` interpreter target from
this repo causes an eager fetch of the toolchain for the host platform.
""",
attrs = {
"platforms": attr.string_list(mandatory = True),
"python_version": attr.string(mandatory = True),
"_rule_name": attr.string(default = "host_toolchain"),
"_rules_python_workspace": attr.label(default = Label("//:WORKSPACE")),
},
)
def _multi_toolchain_aliases_impl(rctx):
rules_python = rctx.attr._rules_python_workspace.repo_name
for python_version, repository_name in rctx.attr.python_versions.items():
file = "{}/defs.bzl".format(python_version)
rctx.file(file, content = """\
# Generated by python/private/toolchains_repo.bzl
load("@@{rules_python}//python:pip.bzl", _compile_pip_requirements = "compile_pip_requirements")
load("@@{rules_python}//python/private:deprecation.bzl", "with_deprecation")
load("@@{rules_python}//python/private:text_util.bzl", "render")
load("@@{rules_python}//python:py_binary.bzl", _py_binary = "py_binary")
load("@@{rules_python}//python:py_test.bzl", _py_test = "py_test")
load(
"@@{rules_python}//python/entry_points:py_console_script_binary.bzl",
_py_console_script_binary = "py_console_script_binary",
)
def _with_deprecation(kwargs, *, name):
kwargs["python_version"] = "{python_version}"
return with_deprecation.symbol(
kwargs,
symbol_name = name,
old_load = "@{name}//{python_version}:defs.bzl",
new_load = "@rules_python//python:{{}}.bzl".format(name),
snippet = render.call(name, **{{k: repr(v) for k,v in kwargs.items()}})
)
def py_binary(**kwargs):
return _py_binary(**_with_deprecation(kwargs, name = "py_binary"))
def py_console_script_binary(**kwargs):
return _py_console_script_binary(**_with_deprecation(kwargs, name = "py_console_script_binary"))
def py_test(**kwargs):
return _py_test(**_with_deprecation(kwargs, name = "py_test"))
def compile_pip_requirements(**kwargs):
return _compile_pip_requirements(**_with_deprecation(kwargs, name = "compile_pip_requirements"))
""".format(
repository_name = repository_name,
name = rctx.attr.name,
python_version = python_version,
rules_python = rules_python,
))
rctx.file("{}/BUILD.bazel".format(python_version), "")
pip_bzl = """\
# Generated by python/private/toolchains_repo.bzl
load("@@{rules_python}//python:pip.bzl", "pip_parse", _multi_pip_parse = "multi_pip_parse")
def multi_pip_parse(name, requirements_lock, **kwargs):
return _multi_pip_parse(
name = name,
python_versions = {python_versions},
requirements_lock = requirements_lock,
minor_mapping = {minor_mapping},
**kwargs
)
""".format(
python_versions = rctx.attr.python_versions.keys(),
minor_mapping = render.indent(render.dict(rctx.attr.minor_mapping), indent = " " * 8).lstrip(),
rules_python = rules_python,
)
rctx.file("pip.bzl", content = pip_bzl)
rctx.file("BUILD.bazel", "")
multi_toolchain_aliases = repository_rule(
_multi_toolchain_aliases_impl,
attrs = {
"minor_mapping": attr.string_dict(doc = "The mapping between `X.Y` and `X.Y.Z` python version values"),
"python_versions": attr.string_dict(doc = "The Python versions."),
"_rules_python_workspace": attr.label(default = Label("//:WORKSPACE")),
},
)
def sanitize_platform_name(platform):
return platform.replace("-", "_")
def _get_host_platform(*, rctx, logger, python_version, os_name, cpu_name, platforms):
"""Gets the host platform.
Args:
rctx: {type}`repository_ctx`.
logger: {type}`struct`.
python_version: {type}`string`.
os_name: {type}`str` the host OS name.
cpu_name: {type}`str` the host CPU name.
platforms: {type}`list[str]` the list of loaded platforms.
Returns:
The host platform.
"""
candidates = []
for platform in platforms:
meta = PLATFORMS[platform]
if meta.os_name == os_name and meta.arch == cpu_name:
candidates.append(platform)
if len(candidates) == 1:
return candidates[0]
if candidates:
env_var = "RULES_PYTHON_REPO_TOOLCHAIN_{}_{}_{}".format(
python_version.replace(".", "_"),
os_name.upper(),
cpu_name.upper(),
)
preference = repo_utils.getenv(rctx, env_var)
if preference == None:
logger.info("Consider using '{}' to select from one of the platforms: {}".format(
env_var,
candidates,
))
elif preference not in candidates:
return logger.fail("Please choose a preferred interpreter out of the following platforms: {}".format(candidates))
else:
candidates = [preference]
if candidates:
return candidates[0]
return logger.fail("Could not find a compatible 'host' python for '{os_name}', '{cpu_name}' from the loaded platforms: {platforms}".format(
os_name = os_name,
cpu_name = cpu_name,
platforms = platforms,
))