fix incorrect transition outputs computation

Author: rickeylev

python/private/builders.bzl

@@ -217,7 +217,7 @@ def _TransitionBuilder(implementation = None, inputs = None, outputs = None, **k
         implementation = _Optional(implementation),
         inputs = _SetBuilder(inputs),
         outputs = _SetBuilder(outputs),
-        kwargs = kwargs,
+        extra_kwargs = kwargs,
         build = lambda *a, **k: _TransitionBuilder_build(self, *a, **k),
     )
     return self
@@ -227,7 +227,7 @@ def _TransitionBuilder_build(self):
         implementation = self.implementation.get(),
         inputs = self.inputs.build(),
         outputs = self.outputs.build(),
-        **self.kwargs
+        **self.extra_kwargs
     )
 
 def _SetBuilder(initial = None):

python/private/py_executable.bzl

@@ -1775,12 +1775,8 @@ def create_executable_rule_builder(implementation, **kwargs):
         ] + _CC_TOOLCHAINS,
         cfg = builders.TransitionBuilder(
             implementation = _transition_executable_impl,
-            inputs = [
-                _PYTHON_VERSION_FLAG,
-            ],
-            outputs = [
-                _PYTHON_VERSION_FLAG,
-            ],
+            inputs = [_PYTHON_VERSION_FLAG],
+            outputs = [_PYTHON_VERSION_FLAG],
         ),
         **kwargs
     )

tests/support/sh_py_run_test.bzl

@@ -26,7 +26,9 @@ load("//python/private:toolchain_types.bzl", "TARGET_TOOLCHAIN_TYPE")  # buildif
 load("//tests/support:support.bzl", "VISIBLE_FOR_TESTING")
 
 def _perform_transition_impl(input_settings, attr, base_impl):
-    settings = base_impl(input_settings, attr) | dict(input_settings)
+    settings = {k: input_settings[k] for k in _RECONFIG_INHERITED_OUTPUTS if k in input_settings}
+    settings.update(base_impl(input_settings, attr))
+
     settings[VISIBLE_FOR_TESTING] = True
     settings["//command_line_option:build_python_zip"] = attr.build_python_zip
     if attr.bootstrap_impl:
@@ -46,6 +48,7 @@ _RECONFIG_OUTPUTS = _RECONFIG_INPUTS + [
     "//command_line_option:build_python_zip",
     VISIBLE_FOR_TESTING,
 ]
+_RECONFIG_INHERITED_OUTPUTS = [v for v in _RECONFIG_OUTPUTS if v in _RECONFIG_INPUTS]
 
 _RECONFIG_ATTRS = {
     "bootstrap_impl": attr.string(),

tests/toolchains/python_toolchain_test.py

@@ -3,6 +3,7 @@
 import pathlib
 import sys
 import unittest
+import pprint
 
 from python.runfiles import runfiles
 
@@ -18,7 +19,13 @@ def test_expected_toolchain_matches(self):
         settings = json.loads(pathlib.Path(settings_path).read_text())
 
         expected = "python_{}".format(expect_version.replace(".", "_"))
-        self.assertIn(expected, settings["toolchain_label"], str(settings))
+        msg = (
+            "Expected toolchain not found\n" +
+            f"Expected toolchain label to contain: {expected}\n" +
+            "Actual build settings:\n" +
+            pprint.pformat(settings)
+        )
+        self.assertIn(expected, settings["toolchain_label"], msg)
 
         actual = "{v.major}.{v.minor}.{v.micro}".format(v=sys.version_info)
         self.assertEqual(actual, expect_version)