fix: do not include transitive sources from pyi_deps in runtime runfiles

CHANGELOG.md

@@ -29,6 +29,9 @@ Unreleased changes are tracked as individual files in the [news/](./news)
 directory, or view the [latest generated
 changelog](https://rules-python.readthedocs.io/en/latest/changelog.html).
 
+### Fixed
+* Fixed {attr}`py_library.pyi_deps` being erroneously included in {obj}`PyInfo.transitive_sources` and propagated into downstream binary and test runfiles.
+
 {#v2-4-0}
 ## [2.4.0] - 2026-09-22
 

python/private/common.bzl

@@ -412,7 +412,14 @@ def create_py_info(
     for target in ctx.attr.pyi_deps:
         # PyInfo may not be present e.g. cc_library rules.
         if PyInfo in target or (BuiltinPyInfo != None and BuiltinPyInfo in target):
-            py_info.merge(_get_py_info(target))
+            info = _get_py_info(target)
+            py_info.imports.add(info.imports)
+            if hasattr(info, "transitive_pyi_files"):
+                py_info.transitive_pyi_files.add(info.transitive_pyi_files)
+            if hasattr(info, "transitive_original_sources"):
+                py_info.transitive_original_sources.add(info.transitive_original_sources)
+            elif hasattr(info, "transitive_sources"):
+                py_info.transitive_original_sources.add(info.transitive_sources)
 
     py_info.transitive_sources.add(required_py_files)
 

tests/base_rules/base_tests.bzl

@@ -100,6 +100,9 @@ def _test_py_info_populated_impl(env, target):
         "{package}/lib2.pyi",
         "{package}/subject.pyi",
     ])
+    info.transitive_sources().contains_exactly([
+        "{package}/test_py_info_populated_subject.py",
+    ])
 
 _tests.append(_test_py_info_populated)
 

tests/base_rules/py_executable_base_tests.bzl

@@ -519,6 +519,43 @@ def _test_py_runtime_info_provided_impl(env, target):
 
 _tests.append(_test_py_runtime_info_provided)
 
+def _test_pyi_deps_not_in_runfiles(name, config):
+    rt_util.helper_target(
+        py_library,
+        name = name + "_types",
+        srcs = [rt_util.empty_file(name + "_type_stub.py")],
+    )
+    rt_util.helper_target(
+        py_library,
+        name = name + "_lib",
+        srcs = [rt_util.empty_file(name + "_lib.py")],
+        pyi_deps = [name + "_types"],
+    )
+    rt_util.helper_target(
+        config.rule,
+        name = name + "_subject",
+        srcs = [name + "_main.py"],
+        main = name + "_main.py",
+        deps = [name + "_lib"],
+    )
+    analysis_test(
+        name = name,
+        impl = _test_pyi_deps_not_in_runfiles_impl,
+        target = name + "_subject",
+    )
+
+def _test_pyi_deps_not_in_runfiles_impl(env, target):
+    target = env.expect.that_target(target)
+    target.runfiles().contains_at_least([
+        "{workspace}/{package}/{test_name}_main.py",
+        "{workspace}/{package}/{test_name}_lib.py",
+    ])
+    target.runfiles().not_contains(
+        "{workspace}/{package}/{test_name}_type_stub.py",
+    )
+
+_tests.append(_test_pyi_deps_not_in_runfiles)
+
 def _test_venv_output_prefix_with_path_separators(name, config):
     rt_util.helper_target(
         config.rule,