Fix Windows hopefully

Author: philsc

docs/toolchains.md

@@ -516,7 +516,7 @@ To run the interpreter that Bazel will use, you can use the
 `@rules_python//python/bin:python` target. This is a binary target with
 the executable pointing at the `python3` binary plus the relevent runfiles.
 
-```
+```console
 $ bazel run @rules_python//python/bin:python
 Python 3.11.1 (main, Jan 16 2023, 22:41:20) [Clang 15.0.7 ] on linux
 Type "help", "copyright", "credits" or "license" for more information.
@@ -528,14 +528,23 @@ Type "help", "copyright", "credits" or "license" for more information.
 ```
 
 You can also access a specific binary's interpreter this way by using the
-`@rules_python//python/bin:python_src` target.
+`@rules_python//python/bin:python_src` target. In the example below, it is
+assumed that the `@rules_python//tools/publish:twine` binary is fixed at Python
+3.11.
 
-```
-$ bazel run @rules_python//python/bin:python --@rules_python//python/bin:interpreter_src=//path/to:bin
+```console
+$ bazel run @rules_python//python/bin:python --@rules_python//python/bin:interpreter_src=@rules_python//tools/publish:twine
+Python 3.11.1 (main, Jan 16 2023, 22:41:20) [Clang 15.0.7 ] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>>
+$ bazel run @rules_python//python/bin:python --@rules_python//python/bin:interpreter_src=@rules_python//tools/publish:twine --@rules_python//python/config_settings:python_version=3.12
 Python 3.11.1 (main, Jan 16 2023, 22:41:20) [Clang 15.0.7 ] on linux
 Type "help", "copyright", "credits" or "license" for more information.
 >>>
 ```
+Despite setting the Python version explicitly to 3.12 in the example above, the
+interpreter comes from the `@rules_python//tools/publish:twine` binary. That is
+a fixed version.
 
 :::{note}
 The `python` target does not provide access to any modules from `py_*`

tests/interpreter/BUILD.bazel

@@ -14,25 +14,31 @@
 
 load("//tests/support:sh_py_run_test.bzl", "py_reconfig_test")
 
+PYTHON_VERSIONS_TO_TEST = (
+    "3.10",
+    "3.11",
+    "3.12",
+)
+
 [py_reconfig_test(
     name = "python_version_%s_test" % python_version,
     srcs = ["interpreter_test.py"],
     data = [
         "//python/bin:python",
     ],
     env = {
-        "EXPECTED_PYTHON_VERSION": python_version,
+        # Both the interpreter and the test itself are expected to run under
+        # the same version.
+        "EXPECTED_INTERPRETER_VERSION": python_version,
+        "EXPECTED_SELF_VERSION": python_version,
+        "PYTHON_BIN": "$(location //python/bin:python)",
     },
     main = "interpreter_test.py",
     python_version = python_version,
     deps = [
         "//python/runfiles",
     ],
-) for python_version in (
-    "3.10",
-    "3.11",
-    "3.12",
-)]
+) for python_version in PYTHON_VERSIONS_TO_TEST]
 
 [py_reconfig_test(
     name = "python_src_%s_test" % python_version,
@@ -41,16 +47,18 @@ load("//tests/support:sh_py_run_test.bzl", "py_reconfig_test")
         "//python/bin:python",
     ],
     env = {
-        "EXPECTED_PYTHON_VERSION": "3.11",
+        # Since we're grabbing the interpreter from a binary with a fixed
+        # version, we expect to always see that version. It doesn't matter what
+        # Python version the test itself is running with.
+        "EXPECTED_INTERPRETER_VERSION": "3.11",
+        # The test itself is still running under different Python versions.
+        "EXPECTED_SELF_VERSION": python_version,
+        "PYTHON_BIN": "$(rootpath //python/bin:python)",
     },
     main = "interpreter_test.py",
     python_src = "//tools/publish:twine",
     python_version = python_version,
     deps = [
         "//python/runfiles",
     ],
-) for python_version in (
-    "3.10",
-    "3.11",
-    "3.12",
-)]
+) for python_version in PYTHON_VERSIONS_TO_TEST]

tests/interpreter/interpreter_test.py

@@ -14,6 +14,7 @@
 
 import os
 import subprocess
+import sys
 import unittest
 
 from python.runfiles import runfiles
@@ -22,11 +23,17 @@
 class InterpreterTest(unittest.TestCase):
     def setUp(self):
         r = runfiles.Create()
-        self.interpreter = r.Rlocation("rules_python/python/bin/python3")
+        self.interpreter = os.environ["PYTHON_BIN"]
 
-    def test_version(self):
+    def test_self_version(self):
+        """Performs a sanity check on the Python version used for this test."""
+        expected_version = os.environ["EXPECTED_SELF_VERSION"]
+        v = sys.version_info
+        self.assertEqual(expected_version, f"{v.major}.{v.minor}")
+
+    def test_interpreter_version(self):
         """Validates that we can successfully execute arbitrary code from the CLI."""
-        expected_version = os.environ["EXPECTED_PYTHON_VERSION"]
+        expected_version = os.environ["EXPECTED_INTERPRETER_VERSION"]
 
         result = subprocess.check_output(
             [self.interpreter],