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Diffstat (limited to 'python/extensions/python.bzl')
| -rw-r--r-- | python/extensions/python.bzl | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/python/extensions/python.bzl b/python/extensions/python.bzl new file mode 100644 index 0000000..2d4032a --- /dev/null +++ b/python/extensions/python.bzl @@ -0,0 +1,258 @@ +# Copyright 2023 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. + +"Python toolchain module extensions for use with bzlmod" + +load("//python:repositories.bzl", "python_register_toolchains") +load("//python/extensions/private:pythons_hub.bzl", "hub_repo") +load("//python/private:toolchains_repo.bzl", "multi_toolchain_aliases") + +# This limit can be increased essentially arbitrarily, but doing so will cause a rebuild of all +# targets using any of these toolchains due to the changed repository name. +_MAX_NUM_TOOLCHAINS = 9999 +_TOOLCHAIN_INDEX_PAD_LENGTH = len(str(_MAX_NUM_TOOLCHAINS)) + +def _toolchain_prefix(index, name): + """Prefixes the given name with the index, padded with zeros to ensure lexicographic sorting. + + Examples: + _toolchain_prefix( 2, "foo") == "_0002_foo_" + _toolchain_prefix(2000, "foo") == "_2000_foo_" + """ + return "_{}_{}_".format(_left_pad_zero(index, _TOOLCHAIN_INDEX_PAD_LENGTH), name) + +def _left_pad_zero(index, length): + if index < 0: + fail("index must be non-negative") + return ("0" * length + str(index))[-length:] + +# Printing a warning msg not debugging, so we have to disable +# the buildifier check. +# buildifier: disable=print +def _print_warn(msg): + print("WARNING:", msg) + +def _python_register_toolchains(name, toolchain_attr, version_constraint): + """Calls python_register_toolchains and returns a struct used to collect the toolchains. + """ + python_register_toolchains( + name = name, + python_version = toolchain_attr.python_version, + register_coverage_tool = toolchain_attr.configure_coverage_tool, + ignore_root_user_error = toolchain_attr.ignore_root_user_error, + set_python_version_constraint = version_constraint, + ) + return struct( + python_version = toolchain_attr.python_version, + set_python_version_constraint = str(version_constraint), + name = name, + ) + +def _python_impl(module_ctx): + # The toolchain info structs to register, in the order to register them in. + toolchains = [] + + # We store the default toolchain separately to ensure it is the last + # toolchain added to toolchains. + default_toolchain = None + + # Map of string Major.Minor to the toolchain name and module name + global_toolchain_versions = {} + + for mod in module_ctx.modules: + module_toolchain_versions = [] + + for toolchain_attr in mod.tags.toolchain: + toolchain_version = toolchain_attr.python_version + toolchain_name = "python_" + toolchain_version.replace(".", "_") + + # Duplicate versions within a module indicate a misconfigured module. + if toolchain_version in module_toolchain_versions: + _fail_duplicate_module_toolchain_version(toolchain_version, mod.name) + module_toolchain_versions.append(toolchain_version) + + # Ignore version collisions in the global scope because there isn't + # much else that can be done. Modules don't know and can't control + # what other modules do, so the first in the dependency graph wins. + if toolchain_version in global_toolchain_versions: + _warn_duplicate_global_toolchain_version( + toolchain_version, + first = global_toolchain_versions[toolchain_version], + second_toolchain_name = toolchain_name, + second_module_name = mod.name, + ) + continue + global_toolchain_versions[toolchain_version] = struct( + toolchain_name = toolchain_name, + module_name = mod.name, + ) + + # Only the root module and rules_python are allowed to specify the default + # toolchain for a couple reasons: + # * It prevents submodules from specifying different defaults and only + # one of them winning. + # * rules_python needs to set a soft default in case the root module doesn't, + # e.g. if the root module doesn't use Python itself. + # * The root module is allowed to override the rules_python default. + if mod.is_root: + # A single toolchain is treated as the default because it's unambiguous. + is_default = toolchain_attr.is_default or len(mod.tags.toolchain) == 1 + elif mod.name == "rules_python" and not default_toolchain: + # We don't do the len() check because we want the default that rules_python + # sets to be clearly visible. + is_default = toolchain_attr.is_default + else: + is_default = False + + # We have already found one default toolchain, and we can only have + # one. + if is_default and default_toolchain != None: + _fail_multiple_default_toolchains( + first = default_toolchain.name, + second = toolchain_name, + ) + + toolchain_info = _python_register_toolchains( + toolchain_name, + toolchain_attr, + version_constraint = not is_default, + ) + + if is_default: + default_toolchain = toolchain_info + else: + toolchains.append(toolchain_info) + + # A default toolchain is required so that the non-version-specific rules + # are able to match a toolchain. + if default_toolchain == None: + fail("No default Python toolchain configured. Is rules_python missing `is_default=True`?") + + # The last toolchain in the BUILD file is set as the default + # toolchain. We need the default last. + toolchains.append(default_toolchain) + + if len(toolchains) > _MAX_NUM_TOOLCHAINS: + fail("more than {} python versions are not supported".format(_MAX_NUM_TOOLCHAINS)) + + # Create the pythons_hub repo for the interpreter meta data and the + # the various toolchains. + hub_repo( + name = "pythons_hub", + default_python_version = default_toolchain.python_version, + toolchain_prefixes = [ + _toolchain_prefix(index, toolchain.name) + for index, toolchain in enumerate(toolchains) + ], + toolchain_python_versions = [t.python_version for t in toolchains], + toolchain_set_python_version_constraints = [t.set_python_version_constraint for t in toolchains], + toolchain_user_repository_names = [t.name for t in toolchains], + ) + + # This is require in order to support multiple version py_test + # and py_binary + multi_toolchain_aliases( + name = "python_versions", + python_versions = { + version: entry.toolchain_name + for version, entry in global_toolchain_versions.items() + }, + ) + +def _fail_duplicate_module_toolchain_version(version, module): + fail(("Duplicate module toolchain version: module '{module}' attempted " + + "to use version '{version}' multiple times in itself").format( + version = version, + module = module, + )) + +def _warn_duplicate_global_toolchain_version(version, first, second_toolchain_name, second_module_name): + _print_warn(( + "Ignoring toolchain '{second_toolchain}' from module '{second_module}': " + + "Toolchain '{first_toolchain}' from module '{first_module}' " + + "already registered Python version {version} and has precedence" + ).format( + first_toolchain = first.toolchain_name, + first_module = first.module_name, + second_module = second_module_name, + second_toolchain = second_toolchain_name, + version = version, + )) + +def _fail_multiple_default_toolchains(first, second): + fail(("Multiple default toolchains: only one toolchain " + + "can have is_default=True. First default " + + "was toolchain '{first}'. Second was '{second}'").format( + first = first, + second = second, + )) + +python = module_extension( + doc = """Bzlmod extension that is used to register Python toolchains. +""", + implementation = _python_impl, + tag_classes = { + "toolchain": tag_class( + doc = """Tag class used to register Python toolchains. +Use this tag class to register one or more Python toolchains. This class +is also potentially called by sub modules. The following covers different +business rules and use cases. + +Toolchains in the Root Module + +This class registers all toolchains in the root module. + +Toolchains in Sub Modules + +It will create a toolchain that is in a sub module, if the toolchain +of the same name does not exist in the root module. The extension stops name +clashing between toolchains in the root module and toolchains in sub modules. +You cannot configure more than one toolchain as the default toolchain. + +Toolchain set as the default version + +This extension will not create a toolchain that exists in a sub module, +if the sub module toolchain is marked as the default version. If you have +more than one toolchain in your root module, you need to set one of the +toolchains as the default version. If there is only one toolchain it +is set as the default toolchain. + +Toolchain repository name + +A toolchain's repository name uses the format `python_{major}_{minor}`, e.g. +`python_3_10`. The `major` and `minor` components are +`major` and `minor` are the Python version from the `python_version` attribute. +""", + attrs = { + "configure_coverage_tool": attr.bool( + mandatory = False, + doc = "Whether or not to configure the default coverage tool for the toolchains.", + ), + "ignore_root_user_error": attr.bool( + default = False, + doc = "Whether the check for root should be ignored or not. This causes cache misses with .pyc files.", + mandatory = False, + ), + "is_default": attr.bool( + mandatory = False, + doc = "Whether the toolchain is the default version", + ), + "python_version": attr.string( + mandatory = True, + doc = "The Python version, in `major.minor` format, e.g '3.12', to create a toolchain for.", + ), + }, + ), + }, +) |