match_object() - Do not try to serialize identity functions (#22)

Author: bblommers

localstack_snapshot/snapshots/prototype.py

@@ -183,14 +183,21 @@ def _convert_object_to_dict(obj_):
                 return obj_.value
             elif hasattr(obj_, "__dict__"):
                 # This is an object - let's try to convert it to a dictionary
-                # A  naive approach would be to use the '__dict__' object directly, but that only lists the attributes
+                # A naive approach would be to use the '__dict__' object directly, but that only lists the attributes.
                 # In order to also serialize the properties, we use the __dir__() method
                 # Filtering by everything that is not a method gives us both attributes and properties
-                # We also (still) skip private attributes/properties, so everything that starts with an underscore
+                # We also (still) skip private attributes/properties, so everything that starts with an underscore.
                 return {
                     k: _convert_object_to_dict(getattr(obj_, k))
                     for k in obj_.__dir__()
-                    if not k.startswith("_") and type(getattr(obj_, k, "")).__name__ != "method"
+                    if (
+                        # Skip private attributes
+                        not k.startswith("_")
+                        # Skip everything that's not a method
+                        and type(getattr(obj_, k, "")).__name__ != "method"
+                        # Skip everything that refers to itself (identity functions), as that leads to recursion
+                        and getattr(obj_, k) != obj_
+                    )
                 }
             return obj_
 

tests/test_snapshots.py

@@ -137,6 +137,21 @@ def __init__(self, name):
         sm.match_object("key_a", CustomObject(name="myname"))
         sm._assert_all()
 
+    def test_match_object_with_identity_function(self):
+        class CustomObject:
+            def __init__(self, name):
+                self.name = name
+
+            @property
+            def me_myself_and_i(self):
+                # This would lead to a RecursionError, so we cannot snapshot this method
+                return self
+
+        sm = SnapshotSession(scope_key="A", verify=True, base_file_path="", update=False)
+        sm.recorded_state = {"key_a": {"name": "myname"}}
+        sm.match_object("key_a", CustomObject(name="myname"))
+        sm._assert_all()
+
     def test_match_object_change(self):
         class CustomObject:
             def __init__(self, name):