8000 Provide current_py_toolchain (#731) · jml-derek/rules_python@c49bab3 · GitHub
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Provide current_py_toolchain (bazel-contrib#731)
This commit introduces the current_py_toolchain rule, exposing the PYTHON2 and PYTHON3 "make" variables in bazel rules, analagous to @bazel_tools//tools/cpp:current_cc_toolchain. See https://docs.bazel.build/versions/main/be/make-variables.html#custom_variables Co-authored-by: Thulio Ferraz Assis <3149049+f0rmiga@users.noreply.github.com>
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‎README.md

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@@ -83,6 +83,11 @@ After registration, your Python targets will use the toolchain's interpreter dur
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is still used to 'bootstrap' Python targets (see https://github.com/bazelbuild/rules_python/issues/691).
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You may also find some quirks while using this toolchain. Please refer to [python-build-standalone documentation's _Quirks_ section](https://python-build-standalone.readthedocs.io/en/latest/quirks.html) for details.
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### Toolchain usage in other rules
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Python toolchains can be utilised in other bazel rules, such as `genrule()`, by adding the `toolchains=["@rules_python//python:current_py_toolchain"]` attribute. The path to the python interpreter can be obtained by using the `$(PYTHON2)` and `$(PYTHON3)` ["Make" Variables](https://bazel.build/reference/be/make-variables). See the [`test_current_py_toolchain`](tests/load_from_macro/BUILD) target for an example.
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### "Hello World"
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Once you've imported the rule set into your `WORKSPACE` using any of these

‎docs/python.md

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‎python/BUILD

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@@ -24,6 +24,8 @@ In an ideal renaming, we'd move the packaging rules to a different package so
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that @rules_python//python is only concerned with the core rules.
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"""
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load(":defs.bzl", "current_py_toolchain")
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package(default_visibility = ["//visibility:public"])
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licenses(["notice"]) # Apache 2.0
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"packaging.bzl",
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"pip.bzl",
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])
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current_py_toolchain(
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name = "current_py_toolchain",
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)

‎python/defs.bzl

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@@ -41,6 +41,49 @@ def _add_tags(attrs):
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attrs["tags"] = [_MIGRATION_TAG]
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return attrs
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def _current_py_toolchain_impl(ctx):
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toolchain = ctx.toolchains[ctx.attr._toolchain]
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direct = []
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transitive = []
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vars = {}
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if toolchain.py3_runtime and toolchain.py3_runtime.interpreter:
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direct.append(toolchain.py3_runtime.interpreter)
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transitive.append(toolchain.py3_runtime.files)
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vars["PYTHON3"] = toolchain.py3_runtime.interpreter.path
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if toolchain.py2_runtime and toolchain.py2_runtime.interpreter:
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direct.append(toolchain.py2_runtime.interpreter)
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transitive.append(toolchain.py2_runtime.files)
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vars["PYTHON2"] = toolchain.py2_runtime.interpreter.path
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files = depset(direct, transitive = transitive)
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return [
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toolchain,
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platform_common.TemplateVariableInfo(vars),
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DefaultInfo(
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runfiles = ctx.runfiles(transitive_files = files),
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files = files,
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),
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]
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current_py_toolchain = rule(
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doc = """
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This rule exists so that the current python toolchain can be used in the `toolchains` attribute of
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other rules, such as genrule. It allows exposing a python toolchain after toolchain resolution has
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happened, to a rule which expects a concrete implementation of a toolchain, rather than a
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toolchain_type which could be resolved to that toolchain.
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""",
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implementation = _current_py_toolchain_impl,
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attrs = {
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"_toolchain": attr.string(default = str(Label("@bazel_tools//tools/python:toolchain_type"))),
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},
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toolchains = [
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str(Label("@bazel_tools//tools/python:toolchain_type")),
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],
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)
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def py_library(**attrs):
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"""See the Bazel core [py_library](https://docs.bazel.build/versions/master/be/python.html#py_library) documentation.
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‎tests/load_from_macro/BUILD

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# Allow a test to verify an "outside package" doesn't get included
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visibility = ["//examples/wheel:__pkg__"],
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)
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genrule(
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name = "test_current_py_toolchain",
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srcs = [],
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outs = ["out.txt"],
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cmd = "$(PYTHON3) --version > $(location out.txt)",
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toolchains = ["//python:current_py_toolchain"],
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)

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