refactor: move hermetic Python runtime setup into macro (bazel-contrib#2221)

This stems from conversation in bazel-contrib#2216. Moving the logic into a
loading-phase macro makes it
easier to understand how a repo with a python-build-standalone extracted
archive has
its toolchain defined. This also makes it easier to compare with the
local runtime repo
setup to try and find commonality in the future.

Along the way:
* Remove some Bazel 5 compatibility code: coverage_tool is now always
passed to py_runtime.
(Bazel 5 support was dropped earlier this year and we stopped testing
with it; it's
  likely already broken with Bazel 5).
* Add `semver.to_dict`, which makes it easier to pass into format()
functions.

Author: rickeylev

examples/bzlmod/MODULE.bazel.lock

@@ -0,0 +1,161 @@
+# Copyright 2024 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.
+"""Setup a python-build-standalone based toolchain."""
+
+load("@rules_cc//cc:defs.bzl", "cc_import", "cc_library")
+load("//python:py_runtime.bzl", "py_runtime")
+load("//python:py_runtime_pair.bzl", "py_runtime_pair")
+load("//python/cc:py_cc_toolchain.bzl", "py_cc_toolchain")
+load(":py_exec_tools_toolchain.bzl", "py_exec_tools_toolchain")
+load(":semver.bzl", "semver")
+
+def define_hermetic_runtime_toolchain_impl(
+        *,
+        name,
+        extra_files_glob_include,
+        extra_files_glob_exclude,
+        python_version,
+        python_bin,
+        coverage_tool):
+    """Define a toolchain implementation for a python-build-standalone repo.
+
+    It expected this macro is called in the top-level package of an extracted
+    python-build-standalone repository. See
+    python/private/python_repositories.bzl for how it is invoked.
+
+    Args:
+        name: {type}`str` name used for tools to identify the invocation.
+        extra_files_glob_include: {type}`list[str]` additional glob include
+            patterns for the target runtime files (the one included in
+            binaries).
+        extra_files_glob_exclude: {type}`list[str]` additional glob exclude
+            patterns for the target runtime files.
+        python_version: {type}`str` The Python version, in `major.minor.micro`
+            format.
+        python_bin: {type}`str` The path to the Python binary within the
+            repositoroy.
+        coverage_tool: {type}`str` optional target to the coverage tool to
+            use.
+    """
+    _ = name  # @unused
+    version_info = semver(python_version)
+    version_dict = version_info.to_dict()
+    native.filegroup(
+        name = "files",
+        srcs = native.glob(
+            include = [
+                "bin/**",
+                "extensions/**",
+                "include/**",
+                "libs/**",
+                "share/**",
+            ] + extra_files_glob_include,
+            # Platform-agnostic filegroup can't match on all patterns.
+            allow_empty = True,
+            exclude = [
+                "**/* *",  # Bazel does not support spaces in file names.
+                # Unused shared libraries. `python` executable and the `:libpython` target
+                # depend on `libpython{python_version}.so.1.0`.
+                "lib/libpython{major}.{minor}.so".format(**version_dict),
+                # static libraries
+                "lib/**/*.a",
+                # tests for the standard libraries.
+                "lib/python{major}.{minor}/**/test/**".format(**version_dict),
+                "lib/python{major}.{minor}/**/tests/**".format(**version_dict),
+                "**/__pycache__/*.pyc.*",  # During pyc creation, temp files named *.pyc.NNN are created
+            ] + extra_files_glob_exclude,
+        ),
+    )
+    cc_import(
+        name = "interface",
+        interface_library = "libs/python{major}{minor}.lib".format(**version_dict),
+        system_provided = True,
+    )
+
+    native.filegroup(
+        name = "includes",
+        srcs = native.glob(["include/**/*.h"]),
+    )
+    cc_library(
+        name = "python_headers",
+        deps = select({
+            "@bazel_tools//src/conditions:windows": [":interface"],
+            "//conditions:default": None,
+        }),
+        hdrs = [":includes"],
+        includes = [
+            "include",
+            "include/python{major}.{minor}".format(**version_dict),
+            "include/python{major}.{minor}m".format(**version_dict),
+        ],
+    )
+    cc_library(
+        name = "libpython",
+        hdrs = [":includes"],
+        srcs = select({
+            "@platforms//os:linux": [
+                "lib/libpython{major}.{minor}.so".format(**version_dict),
+                "lib/libpython{major}.{minor}.so.1.0".format(**version_dict),
+            ],
+            "@platforms//os:macos": ["lib/libpython{major}.{minor}.dylib".format(**version_dict)],
+            "@platforms//os:windows": ["python3.dll", "libs/python{major}{minor}.lib".format(**version_dict)],
+        }),
+    )
+
+    native.exports_files(["python", python_bin])
+
+    # Used to only download coverage toolchain when the coverage is collected by
+    # bazel.
+    native.config_setting(
+        name = "coverage_enabled",
+        values = {"collect_code_coverage": "true"},
+        visibility = ["//visibility:private"],
+    )
+
+    py_runtime(
+        name = "py3_runtime",
+        files = [":files"],
+        interpreter = python_bin,
+        interpreter_version_info = {
+            "major": str(version_info.major),
+            "micro": str(version_info.patch),
+            "minor": str(version_info.minor),
+        },
+        # Convert empty string to None
+        coverage_tool = coverage_tool or None,
+        python_version = "PY3",
+        implementation_name = "cpython",
+        # See https://peps.python.org/pep-3147/ for pyc tag infix format
+        pyc_tag = "cpython-{major}{minor}".format(**version_dict),
+    )
+
+    py_runtime_pair(
+        name = "python_runtimes",
+        py2_runtime = None,
+        py3_runtime = ":py3_runtime",
+    )
+
+    py_cc_toolchain(
+        name = "py_cc_toolchain",
+        headers = ":python_headers",
+        libs = ":libpython",
+        python_version = python_version,
+    )
+
+    py_exec_tools_toolchain(
+        name = "py_exec_tools_toolchain",
+        # This macro is called in another repo: use Label() to ensure it
+        # resolves in the rules_python context.
+        precompiler = Label("//tools/precompiler:precompiler"),
+    )

python/private/hermetic_runtime_repo_setup.bzl

@@ -34,6 +34,7 @@ load(":coverage_deps.bzl", "coverage_dep")
 load(":full_version.bzl", "full_version")
 load(":internal_config_repo.bzl", "internal_config_repo")
 load(":repo_utils.bzl", "REPO_DEBUG_ENV_VAR", "repo_utils")
+load(":text_util.bzl", "render")
 load(
     ":toolchains_repo.bzl",
     "host_toolchain",
@@ -246,20 +247,6 @@ def _python_repository_impl(rctx):
 
     python_bin = "python.exe" if ("windows" in platform) else "bin/python3"
 
-    glob_include = []
-    glob_exclude = [
-        "**/* *",  # Bazel does not support spaces in file names.
-        # Unused shared libraries. `python` executable and the `:libpython` target
-        # depend on `libpython{python_version}.so.1.0`.
-        "lib/libpython{python_version}.so".format(python_version = python_short_version),
-        # static libraries
-        "lib/**/*.a",
-        # tests for the standard libraries.
-        "lib/python{python_version}/**/test/**".format(python_version = python_short_version),
-        "lib/python{python_version}/**/tests/**".format(python_version = python_short_version),
-        "**/__pycache__/*.pyc.*",  # During pyc creation, temp files named *.pyc.NNN are created
-    ]
-
     if "linux" in platform:
         # Workaround around https://github.com/indygreg/python-build-standalone/issues/231
         for url in urls:
@@ -281,6 +268,8 @@ def _python_repository_impl(rctx):
                 rctx.delete("share/terminfo")
                 break
 
+    glob_include = []
+    glob_exclude = []
     if rctx.attr.ignore_root_user_error or "windows" in platform:
         glob_exclude += [
             # These pycache files are created on first use of the associated python files.
@@ -295,148 +284,42 @@ def _python_repository_impl(rctx):
         glob_include += [
             "*.exe",
             "*.dll",
-            "bin/**",
             "DLLs/**",
-            "extensions/**",
-            "include/**",
             "Lib/**",
-            "libs/**",
             "Scripts/**",
-            "share/**",
             "tcl/**",
         ]
     else:
-        glob_include += [
-            "bin/**",
-            "extensions/**",
-            "include/**",
+        glob_include.append(
             "lib/**",
-            "libs/**",
-            "share/**",
-        ]
+        )
 
-    if rctx.attr.coverage_tool:
-        if "windows" in platform:
-            coverage_tool = None
-        else:
-            coverage_tool = '"{}"'.format(rctx.attr.coverage_tool)
-
-        coverage_attr_text = """\
-    coverage_tool = select({{
-        ":coverage_enabled": {coverage_tool},
-        "//conditions:default": None
-    }}),
-""".format(coverage_tool = coverage_tool)
+    if "windows" in platform:
+        coverage_tool = None
     else:
-        coverage_attr_text = "    # coverage_tool attribute not supported by this Bazel version"
+        coverage_tool = rctx.attr.coverage_tool
 
     build_content = """\
-# Generated by python/repositories.bzl
+# Generated by python/private/python_repositories.bzl
 
-load("@rules_python//python:py_runtime.bzl", "py_runtime")
-load("@rules_python//python:py_runtime_pair.bzl", "py_runtime_pair")
-load("@rules_python//python/cc:py_cc_toolchain.bzl", "py_cc_toolchain")
-load("@rules_python//python/private:py_exec_tools_toolchain.bzl", "py_exec_tools_toolchain")
+load("@rules_python//python/private:hermetic_runtime_repo_setup.bzl", "define_hermetic_runtime_toolchain_impl")
 
 package(default_visibility = ["//visibility:public"])
 
-filegroup(
-    name = "files",
-    srcs = glob(
-        include = {glob_include},
-        # Platform-agnostic filegroup can't match on all patterns.
-        allow_empty = True,
-        exclude = {glob_exclude},
-    ),
-)
-
-cc_import(
-    name = "interface",
-    interface_library = "libs/python{python_version_nodot}.lib",
-    system_provided = True,
-)
-
-filegroup(
-    name = "includes",
-    srcs = glob(["include/**/*.h"]),
-)
-
-cc_library(
-    name = "python_headers",
-    deps = select({{
-        "@bazel_tools//src/conditions:windows": [":interface"],
-        "//conditions:default": None,
-    }}),
-    hdrs = [":includes"],
-    includes = [
-        "include",
-        "include/python{python_version}",
-        "include/python{python_version}m",
-    ],
-)
-
-cc_library(
-    name = "libpython",
-    hdrs = [":includes"],
-    srcs = select({{
-        "@platforms//os:windows": ["python3.dll", "libs/python{python_version_nodot}.lib"],
-        "@platforms//os:macos": ["lib/libpython{python_version}.dylib"],
-        "@platforms//os:linux": ["lib/libpython{python_version}.so", "lib/libpython{python_version}.so.1.0"],
-    }}),
-)
-
-exports_files(["python", "{python_path}"])
-
-# Used to only download coverage toolchain when the coverage is collected by
-# bazel.
-config_setting(
-    name = "coverage_enabled",
-    values = {{"collect_code_coverage": "true"}},
-    visibility = ["//visibility:private"],
-)
-
-py_runtime(
-    name = "py3_runtime",
-    files = [":files"],
-{coverage_attr}
-    interpreter = "{python_path}",
-    interpreter_version_info = {{
-        "major": "{interpreter_version_info_major}",
-        "minor": "{interpreter_version_info_minor}",
-        "micro": "{interpreter_version_info_micro}",
-    }},
-    python_version = "PY3",
-    implementation_name = 'cpython',
-    pyc_tag = "cpython-{interpreter_version_info_major}{interpreter_version_info_minor}",
-)
-
-py_runtime_pair(
-    name = "python_runtimes",
-    py2_runtime = None,
-    py3_runtime = ":py3_runtime",
-)
-
-py_cc_toolchain(
-    name = "py_cc_toolchain",
-    headers = ":python_headers",
-    libs = ":libpython",
-    python_version = "{python_version}",
-)
-
-py_exec_tools_toolchain(
-    name = "py_exec_tools_toolchain",
-    precompiler = "@rules_python//tools/precompiler:precompiler",
+define_hermetic_runtime_toolchain_impl(
+  name = "define_runtime",
+  extra_files_glob_include = {extra_files_glob_include},
+  extra_files_glob_exclude = {extra_files_glob_exclude},
+  python_version = {python_version},
+  python_bin = {python_bin},
+  coverage_tool = {coverage_tool},
 )
 """.format(
-        glob_exclude = repr(glob_exclude),
-        glob_include = repr(glob_include),
-        python_path = python_bin,
-        python_version = python_short_version,
-        python_version_nodot = python_short_version.replace(".", ""),
-        coverage_attr = coverage_attr_text,
-        interpreter_version_info_major = python_version_info[0],
-        interpreter_version_info_minor = python_version_info[1],
-        interpreter_version_info_micro = python_version_info[2],
+        extra_files_glob_exclude = render.list(glob_exclude),
+        extra_files_glob_include = render.list(glob_include),
+        python_bin = render.str(python_bin),
+        python_version = render.str(rctx.attr.python_version),
+        coverage_tool = render.str(coverage_tool),
     )
     rctx.delete("python")
     rctx.symlink(python_bin, "python")