Fix sys.modules order during loading

python/tank/util/loader.py

@@ -57,8 +57,8 @@ def load_plugin(plugin_file, valid_base_class, alternate_base_classes=None):
     try:
         plugin_spec = importlib.util.spec_from_file_location(module_uid, plugin_file)
         module = importlib.util.module_from_spec(plugin_spec)
-        plugin_spec.loader.exec_module(module)
         sys.modules[module.__name__] = module
+        plugin_spec.loader.exec_module(module)
     except Exception:
         # log the full callstack to make sure that whatever the
         # calling code is doing, this error is logged to help

tests/fixtures/config/hooks/dataclass_hook.py

@@ -0,0 +1,49 @@
+# Copyright (c) 2026 Autodesk.
+#
+# CONFIDENTIAL AND PROPRIETARY
+#
+# This work is provided "AS IS" and subject to the ShotGrid Pipeline Toolkit
+# Source Code License included in this distribution package. See LICENSE.
+# By accessing, using, copying or modifying this work you indicate your
+# agreement to the ShotGrid Pipeline Toolkit Source Code License. All rights
+# not expressly granted therein are reserved by Autodesk.
+"""Case where we check defining a Python dataclass won't fail during hook loading.
+
+The dataclasses module check the `.sys.modules` for the ``Data`` class's ``__module__``
+during type checking, so it should exist in there and not fatally error when loading
+this hook.
+
+This is a regression test for https://github.com/shotgunsoftware/tk-core/pull/1047
+(https://github.com/shotgunsoftware/tk-core/commit/eaaadceafa4b449f819cf9c1b05cba229daaeeab)
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+import sgtk
+
+
+@dataclass(frozen=True)
+class Data:
+    name: str | None
+    number: int | float
+    error: (
+        sgtk.authentication.AuthenticationError
+        | sgtk.authentication.IncompleteCredentials
+        | sgtk.authentication.AuthenticationCancelled
+        | sgtk.authentication.ConsoleLoginNotSupportedError
+        | None
+    ) = None
+
+
+class TestHook(sgtk.get_hook_baseclass()):
+    def execute(self):
+        return Data("foo", 123)
+
+    def second_method(self):
+        return Data(
+            None,
+            -3.1419,
+            error=sgtk.authentication.AuthenticationCancelled(),
+        )

tests/platform_tests/test_application.py

@@ -273,6 +273,20 @@ def test_get_setting(self):
         )
 
 
+class TestDataclassHook(TestApplication):
+    """
+    Test loading, executing and calling ``dataclass_hook``.
+    """
+
+    def test_execute(self):
+        app = self.engine.apps["test_app"]
+        app.execute_hook_by_name("dataclass_hook")
+
+    def test_legacy_format(self):
+        app = self.engine.apps["test_app"]
+        app.execute_hook_expression("dataclass_hook", "second_method")
+
+
 class TestExecuteHookByName(TestApplication):
     """
     Tests execute_hook_by_name