Use explicit __init__.py files instead of implicit creation

MODULE.bazel

@@ -6,9 +6,14 @@ module(
 
 # Do not update to newer versions until you need a specific new feature.
 bazel_dep(name = "rules_license", version = "1.0.0")
-bazel_dep(name = "rules_python", version = "1.7.0")
+bazel_dep(name = "rules_python", version = "2.3.0")
 bazel_dep(name = "bazel_skylib", version = "1.9.0")
 
+# Do not generate __init__.py files for our py_binary and py_test targets.
+# We ship them explicitly.
+rules_python_config = use_extension("@rules_python//python/extensions:config.bzl", "config")
+rules_python_config.explicit_init_py(default = True)
+
 # Only for development
 bazel_dep(name = "platforms", version = "1.0.0", dev_dependency = True)
 bazel_dep(name = "rules_cc", version = "0.2.16", dev_dependency = True)

pkg/BUILD

@@ -67,6 +67,16 @@ filegroup(
     visibility = ["//visibility:public"],
 )
 
+# The top level package marker. Everything importing from `pkg.` must depend on
+# this, since we do not rely on implicit __init__.py creation.
+py_library(
+    name = "init",
+    srcs = ["__init__.py"],
+    imports = [".."],
+    srcs_version = "PY3",
+    visibility = ["//:__subpackages__"],
+)
+
 # Used by pkg_rpm in rpm.bzl.
 py_binary(
     name = "make_rpm",
@@ -92,6 +102,7 @@ py_library(
         "//tests:__subpackages__",
     ],
     deps = [
+        ":init",
         "//pkg/private:archive",
         "//pkg/private:build_info",
         "//pkg/private:helpers",
@@ -108,8 +119,10 @@ py_binary(
 py_library(
     name = "filter_directory_lib",
     srcs = ["filter_directory.py"],
+    imports = [".."],
     srcs_version = "PY3",
     visibility = ["//visibility:public"],
+    deps = [":init"],
 )
 
 exports_files(["verify_archive_test_main.py.tpl"])

pkg/private/BUILD

@@ -60,45 +60,49 @@ config_setting(
     visibility = ["//visibility:public"],
 )
 
+py_library(
+    name = "init",
+    srcs = ["__init__.py"],
+    imports = ["../.."],
+    srcs_version = "PY3",
+    visibility = ["//:__subpackages__"],
+    deps = ["//pkg:init"],
+)
+
 py_library(
     name = "build_info",
-    srcs = [
-        "build_info.py",
-    ],
+    srcs = ["build_info.py"],
     imports = ["../.."],
     srcs_version = "PY3",
     visibility = [
         "//:__subpackages__",
         "//tests:__pkg__",
     ],
+    deps = [":init"],
 )
 
 py_library(
     name = "archive",
-    srcs = [
-        "__init__.py",
-        "archive.py",
-    ],
+    srcs = ["archive.py"],
     imports = ["../.."],
     srcs_version = "PY3",
     visibility = [
         "//:__subpackages__",
         "//tests:__subpackages__",
     ],
+    deps = [":init"],
 )
 
 py_library(
     name = "helpers",
-    srcs = [
-        "__init__.py",
-        "helpers.py",
-    ],
+    srcs = ["helpers.py"],
     imports = ["../.."],
     srcs_version = "PY3",
     visibility = [
         "//:__subpackages__",
         "//tests:__pkg__",
     ],
+    deps = [":init"],
 )
 
 py_library(
@@ -107,4 +111,5 @@ py_library(
     imports = ["../.."],
     srcs_version = "PY3",
     visibility = ["//visibility:public"],
+    deps = [":init"],
 )

pkg/private/deb/BUILD

@@ -58,10 +58,16 @@ py_binary(
 
 py_library(
     name = "make_deb_lib",
-    srcs = ["make_deb.py"],
+    srcs = [
+        "__init__.py",
+        "make_deb.py",
+    ],
     imports = ["../../.."],
     srcs_version = "PY3",
-    visibility = ["//tests/deb:__pkg__"],
+    visibility = [
+        "//tests:__pkg__",
+        "//tests/deb:__pkg__",
+    ],
     deps = [
         "//pkg/private:helpers",
     ],

pkg/private/install.py.tpl

@@ -45,6 +45,25 @@ def locate(short_path, repository):
     return RUNFILES.Rlocation(posixpath.normpath(posixpath.join(repository, short_path)))
 
 
+def _resolve_runfile(path):
+    """Return the real file behind a runfile, so that it can be opened.
+
+    With --enable_runfiles on Windows, Bazel may create a directory junction
+    for a file runfile. Such a junction can not be opened, and
+    os.path.realpath fails on it, so we read the junction target instead.
+    """
+    if os.name != "nt":
+        return os.path.realpath(path)
+    try:
+        target = os.readlink(path)
+    except OSError:
+        # Not a link.
+        return path
+    if target.startswith("\\\\?\\"):
+        target = target[4:]
+    return os.path.join(os.path.dirname(path), target)
+
+
 # This is named "NativeInstaller" because it makes use of "native" python
 # functionality for installing files that should be cross-platform.
 #
@@ -81,10 +100,7 @@ class NativeInstaller(object):
 
     def _do_file_copy(self, src, dest):
         logging.debug("COPY %s <- %s", dest, src)
-        # Windows --enable_runfiles uses directory junctions for every runfile.
-        # Junctions cannot point at files, so open() fails with Permission denied.
-        # Follow the reparse point to the real bazel-out file.
-        src = os.path.realpath(src)
+        src = _resolve_runfile(src)
         # Copy to a temporary directory and then move it to the destination.
         # This ensures code-signed executables on certain platforms
         # behave correctly.

pkg/private/tar/BUILD

@@ -63,11 +63,13 @@ py_binary(
 py_library(
     name = "tar_writer",
     srcs = [
+        "__init__.py",
         "tar_writer.py",
     ],
     imports = ["../../.."],
     srcs_version = "PY3",
     visibility = [
         "//tests:__subpackages__",
     ],
+    deps = ["//pkg/private:init"],
 )

pkg/releasing/BUILD

@@ -36,6 +36,7 @@ py_library(
     ],
     imports = ["../.."],
     srcs_version = "PY3",
+    deps = ["//pkg:init"],
 )
 
 py_binary(

pkg/verify_archive_test_main.py.tpl

@@ -13,10 +13,31 @@
 # limitations under the License.
 """Tests for generated content manifest."""
 
+import os
 import re
 import tarfile
 import unittest
 
+
+def _resolve_junction(path):
+  """Returns the target of path if it is a Windows junction, else path.
+
+  With --enable_runfiles on Windows, Bazel may create a directory junction
+  for a file runfile. Such a junction can not be opened, and
+  os.path.realpath fails on it, so we read the junction target instead.
+  """
+  if os.name != 'nt':
+    return path
+  try:
+    target = os.readlink(path)
+  except OSError:
+    # Not a link.
+    return path
+  if target.startswith('\\\\?\\'):
+    target = target[4:]
+  return os.path.join(os.path.dirname(path), target)
+
+
 class VerifyArchiveTest(unittest.TestCase):
   """Test harness to see if we wrote the content manifest correctly."""
 
@@ -37,7 +58,7 @@ class VerifyArchiveTest(unittest.TestCase):
   def load_tar(self, path):
     self.paths = []
     self.links = {}
-    with tarfile.open(path, 'r:*') as f:
+    with tarfile.open(_resolve_junction(path), 'r:*') as f:
       i = 0
       for info in f:
         self.paths.append(info.name)

tests/BUILD

@@ -97,10 +97,22 @@ py_test(
     srcs_version = "PY3",
     deps = [
         "//pkg/private:archive",
+        "//tests/util:runfiles_util",
         "@rules_python//python/runfiles",
     ],
 )
 
+py_test(
+    name = "explicit_init_test",
+    srcs = ["explicit_init_test.py"],
+    python_version = "PY3",
+    srcs_version = "PY3",
+    deps = [
+        "//pkg/private/deb:make_deb_lib",
+        "//pkg/private/tar:tar_writer",
+    ],
+)
+
 py_test(
     name = "path_test",
     srcs = ["path_test.py"],
@@ -216,6 +228,7 @@ py_test(
     ],
     python_version = "PY3",
     deps = [
+        "//tests/util:runfiles_util",
         "@rules_python//python/runfiles",
     ],
 )

tests/archive_test.py

@@ -16,6 +16,7 @@
 import unittest
 
 from python.runfiles import runfiles
+from tests.util import runfiles_util
 from pkg.private import archive
 
 
@@ -62,11 +63,12 @@ def assertArFileContent(self, arfile, content):
 
   def testEmptyArFile(self):
     self.assertArFileContent(
-        self.data_files.Rlocation("rules_pkg/tests/testdata/empty.ar"),
+        runfiles_util.rlocation(
+            self.data_files, "rules_pkg/tests/testdata/empty.ar"),
         [])
 
   def assertSimpleFileContent(self, names):
-    datafile = self.data_files.Rlocation(
+    datafile = runfiles_util.rlocation(self.data_files,
         "rules_pkg/tests/testdata/" + "_".join(names) + ".ar")
     # pylint: disable=g-complex-comprehension
     content = [{"filename": n,

tests/deb/BUILD

@@ -126,6 +126,7 @@ py_test(
     python_version = "PY3",
     deps = [
         "//pkg/private:archive",
+        "//tests/util:runfiles_util",
         "@rules_python//python/runfiles",
     ],
 )
@@ -204,6 +205,7 @@ py_test(
     python_version = "PY3",
     deps = [
         "//pkg/private:archive",
+        "//tests/util:runfiles_util",
         "@rules_python//python/runfiles",
     ],
 )

tests/deb/pkg_deb_test.py

@@ -23,6 +23,7 @@
 import unittest
 
 from python.runfiles import runfiles
+from tests.util import runfiles_util
 from pkg.private import archive
 
 
@@ -63,9 +64,10 @@ def setUp(self):
     super(PkgDebTest, self).setUp()
     self.runfiles = runfiles.Create()
     # Note: Rlocation requires forward slashes. os.path.join() will not work.
-    self.deb_path = self.runfiles.Rlocation('rules_pkg/tests/deb/fizzbuzz_4.5.6_all.deb')
+    self.deb_path = runfiles_util.rlocation(
+        self.runfiles, 'rules_pkg/tests/deb/fizzbuzz_4.5.6_all.deb')
     self.deb_file = DebInspect(self.deb_path)
-    self.installed_size_file_deb_path = self.runfiles.Rlocation(
+    self.installed_size_file_deb_path = runfiles_util.rlocation(self.runfiles,
         'rules_pkg/tests/deb/fizzbuzz-installed-size-file_1.0.0_all.deb')
     self.installed_size_file_deb_file = DebInspect(self.installed_size_file_deb_path)
 
@@ -235,7 +237,7 @@ def test_triggers(self):
         'some-trigger\n')
 
   def test_changes(self):
-    changes_path = self.runfiles.Rlocation(
+    changes_path = runfiles_util.rlocation(self.runfiles,
         'rules_pkg/tests/deb/fizzbuzz_4.5.6_all.changes')
     with open(changes_path, 'r', encoding='utf-8') as f:
       content = f.read()

tests/deb/pkg_deb_variables_test.py

@@ -21,6 +21,7 @@
 import unittest
 
 from python.runfiles import runfiles
+from tests.util import runfiles_util
 from pkg.private import archive
 
 
@@ -62,7 +63,7 @@ def setUp(self):
         # my_package_variables provides arch=target_arch, label="some_value", so:
         #   package = "pkg-$(label)" -> "pkg-some_value"
         #   architecture = "$(arch)" -> "target_arch"
-        deb_path = self.runfiles.Rlocation(
+        deb_path = runfiles_util.rlocation(self.runfiles,
             "rules_pkg/tests/deb/pkg-some_value_1.0_target_arch.deb"
         )
         self.deb_file = DebInspect(deb_path)

tests/explicit_init_test.py

@@ -0,0 +1,38 @@
+# Copyright 2026 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.
+"""Checks that our Python packages ship explicit __init__.py files.
+
+This test runs with legacy_create_init = 0, so any package whose
+__init__.py is not in the runfiles would be imported as an implicit
+namespace package, which has no __file__.
+"""
+
+import importlib
+import unittest
+
+
+class ExplicitInitTest(unittest.TestCase):
+
+    def test_packages_are_regular_packages(self):
+        for name in ("pkg", "pkg.private", "pkg.private.deb", "pkg.private.tar"):
+            with self.subTest(package=name):
+                module = importlib.import_module(name)
+                self.assertIsNotNone(
+                    module.__file__,
+                    "%s is a namespace package; add its __init__.py to srcs" % name,
+                )
+
+
+if __name__ == "__main__":
+    unittest.main()