From 70b3edd51c1465b5c23c877e3fd4cf036a8c98d1 Mon Sep 17 00:00:00 2001
From: Gleb Kanterov <gleb.kanterov@databricks.com>
Date: Thu, 20 Mar 2025 11:47:27 +0100
Subject: [PATCH 1/2] [Python] Add tests for recursive imports

---
 .../python/databricks/bundles/core/_load.py   |  2 +-
 .../databricks_tests/core/test_import.py      | 61 +++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)
 create mode 100644 experimental/python/databricks_tests/core/test_import.py

diff --git a/experimental/python/databricks/bundles/core/_load.py b/experimental/python/databricks/bundles/core/_load.py
index 8eb5ebe5d0..e643dc4b1b 100644
--- a/experimental/python/databricks/bundles/core/_load.py
+++ b/experimental/python/databricks/bundles/core/_load.py
@@ -7,7 +7,7 @@
 from types import ModuleType
 from typing import Any, Iterable
 
-from databricks.bundles.core import Diagnostics
+from databricks.bundles.core._diagnostics import Diagnostics
 from databricks.bundles.core._location import Location
 from databricks.bundles.core._resource import Resource
 from databricks.bundles.core._resources import Resources
diff --git a/experimental/python/databricks_tests/core/test_import.py b/experimental/python/databricks_tests/core/test_import.py
new file mode 100644
index 0000000000..f584eaa5fd
--- /dev/null
+++ b/experimental/python/databricks_tests/core/test_import.py
@@ -0,0 +1,61 @@
+import sys
+from types import ModuleType
+
+import pytest
+
+
+@pytest.fixture(scope="function")
+def reset_sys_modules():
+    """
+    Reset sys.module before test and restore it after test.
+    """
+
+    original_modules = sys.modules.copy()
+    try:
+        import databricks.bundles
+
+        for module in original_modules.keys():
+            if is_subpackage(module, databricks.bundles):
+                del sys.modules[module]
+
+        del sys.modules[databricks.bundles.__package__]
+
+        yield
+    finally:
+        # Clear any modifications and restore the original modules
+        sys.modules.clear()
+        sys.modules.update(original_modules)
+
+
+def test_import_regression(reset_sys_modules):
+    """
+    We don't want importing databricks.bundles.core to import any of resources.
+
+    We refer to resources in type signatures (e.g. in Resources or @job_mutator),
+    unless we use forward references (e.g. "Job" instead of Job) we can create a
+    cycling dependency resulting in a runtime error.
+
+    We want every package with resources (e.g., databricks.bundles.jobs) to be loaded
+    only when needed.
+    """
+
+    import databricks.bundles.core
+
+    assert databricks.bundles.core
+
+    import databricks.bundles
+
+    for module in sys.modules.keys():
+        if is_subpackage(module, databricks.bundles):
+            is_core = module == databricks.bundles.core.__package__
+            is_core_subpackage = is_subpackage(module, databricks.bundles.core)
+
+            assert is_core or is_core_subpackage, (
+                f"Unexpected loaded module AFTER loading core: {module}"
+            )
+
+
+def is_subpackage(module: str, parent: ModuleType) -> bool:
+    assert parent.__package__
+
+    return module.startswith(parent.__package__ + ".")

From b111e4b6a179caa7417057a7dcbf2f91af77b539 Mon Sep 17 00:00:00 2001
From: Gleb Kanterov <gleb.kanterov@databricks.com>
Date: Thu, 27 Mar 2025 16:59:20 +0100
Subject: [PATCH 2/2] Fix lint

---
 experimental/python/databricks_tests/core/test_import.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/experimental/python/databricks_tests/core/test_import.py b/experimental/python/databricks_tests/core/test_import.py
index f584eaa5fd..732c52a7cb 100644
--- a/experimental/python/databricks_tests/core/test_import.py
+++ b/experimental/python/databricks_tests/core/test_import.py
@@ -18,6 +18,7 @@ def reset_sys_modules():
             if is_subpackage(module, databricks.bundles):
                 del sys.modules[module]
 
+        assert databricks.bundles.__package__
         del sys.modules[databricks.bundles.__package__]
 
         yield