如何指定在Bazel中使用哪个Python工具链？

Question

我如何配置Bazel来选择一个工具链而不是另一个工具链？我可以通过命令行参数来定义要使用的工具链，或者指定应该在特定目标中使用的工具链。

当前在我的工作区文件中定义了两个工具链。我有两个Python工具链。其中一个从源代码构建Python，并将其包含在可执行的.zip输出中，而另一个则没有。

构建时，使用的工具链始终是注册的第一个工具链。在这种情况下，即使构建目标从python3_tooolchain导入requirement，也会使用hermetic_python3_toolchain。

# WORKSPACE

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
load("@rules_python//python:pip.bzl", "pip_install")

http_archive(
    name = "rules_python",
    url = "https://github.com/bazelbuild/rules_python/releases/download/0.5.0/rules_python-0.5.0.tar.gz",
    sha256 = "cd6730ed53a002c56ce4e2f396ba3b3be262fd7cb68339f0377a45e8227fe332",
)

# Non-hermetic toolchain 
register_toolchains("//src:python3_toolchain")

pip_install(
   quiet = False,
   name = "python_dependencies",
   requirements = "//:requirements.txt",
   python_interpreter = "/usr/bin/python3"
)

load("@python_dependencies//:requirements.bzl", "requirement")




# Hermetic toolchain 

_py_configure = """
if [[ "$OSTYPE" == "darwin"* ]]; then
    ./configure --prefix=$(pwd)/bazel_install --with-openssl=$(brew --prefix openssl)
else
    ./configure --prefix=$(pwd)/bazel_install
fi
"""

http_archive(
    name = "hermetic_interpreter",
    urls = ["https://www.python.org/ftp/python/3.11.0/Python-3.11.0.tar.xz"],
    sha256 = "a57dc82d77358617ba65b9841cee1e3b441f386c3789ddc0676eca077f2951c3",
    strip_prefix = "Python-3.11.0",
    patch_cmds = [
        "mkdir $(pwd)/bazel_install",
        _py_configure,
        "make",
        "make install",
        "ln -s bazel_install/bin/python3 python_bin",
    ],
    build_file_content = """
exports_files(["python_bin"])
filegroup(
    name = "files",
    srcs = glob(["bazel_install/**"], exclude = ["**/* *"]),
    visibility = ["//visibility:public"],
)
""",
)

pip_install(
    name = "hermetic_python3_dependencies",
    requirements = "//:requirements.txt",
    python_interpreter_target = "@hermetic_interpreter//:python_bin",
)
load("@hermetic_python3_dependencies//:requirements.bzl", "requirement")




load("@rules_python//python:defs.bzl", "py_binary")
load("@rules_python//python:defs.bzl", "py_library")

register_toolchains("//src:hermetic_python3_toolchain")

# src/BUILD

load("@bazel_tools//tools/python:toolchain.bzl", "py_runtime_pair")

# Non-hermetic toolchain 
py_runtime(
    name = "python3_runtime",
    interpreter_path = "/usr/bin/python3",
    python_version = "PY3",
    visibility = ["//visibility:public"],
)

py_runtime_pair(
    name = "python3_runtime_pair",
    py2_runtime = None,
    py3_runtime = ":python3_runtime",
)

toolchain(
    name = "python3_toolchain",
    toolchain = ":python3_runtime_pair",
    toolchain_type = "@bazel_tools//tools/python:toolchain_type",
)

# Hermetic toolchain

py_runtime(
    name = "hermetic_python3_runtime",
    files = ["@hermetic_interpreter//:files"],
    interpreter = "@hermetic_interpreter//:python_bin",
    python_version = "PY3",
    visibility = ["//visibility:public"],
)

py_runtime_pair(
    name = "hermetic_python3_runtime_pair",
    py2_runtime = None,
    py3_runtime = ":hermetic_python3_runtime",
)

toolchain(
    name = "hermetic_python3_toolchain",
    toolchain = ":hermetic_python3_runtime_pair",
    toolchain_type = "@bazel_tools//tools/python:toolchain_type",
)


package(default_visibility = ["//visibility:public"])

# /src/some_tool/BUILD

load("@hermetic_python3_dependencies//:requirements.bzl", "requirement") # Can load this rule from either `hermetic_python3_dependencies` or `python3_dependencies`, but does not seem to make a difference 

py_binary(
    name = "some-tool",
    main = "some_tool.py",
    srcs = ["some_tool_file.py"],
    python_version = "PY3",
    srcs_version = "PY3",
    deps = [
        requirement("requests"),
        "//src/common/some-library:library",
    ]
)

package(default_visibility = ["//visibility:public"])

Answer 1

考虑升级rules_python，因为该规则集包含自python/releases/tag/0.7.0以来的封闭python工具链。

如果这不是一种选择：

目前，您正在WORKSPACE.bazel文件中注册两个工具链，bazel将使用它的工具链分解来选择其中的一个。您可以使用--toolchain_resolution_debug=regex标志调试该分辨率，以查看发生了什么。

如果要强制整个构建使用其中一个工具链，请从WORKSPACE.bazel文件中删除注册工具链并创建一个.bazelrc。

build:hermetic_python --extra_toolchains=//src:hermetic_python3_toolchain
build:system_python --extra_toolchains=//src:python3_toolchain

现在，您可以使用bazel build --config=hermetic_python或bazel build --config=system_python在这些工具链之间切换。

但是，请注意，这并不影响用于运行pip_parse()的python工具链中的哪个。在加载requirement()函数时，您需要格外小心。只需通过load()函数，就可以强制对pip_parse()进行计算，并对相应的python解释器进行获取/编译。