Better type checking for Null types (#3557)

aws-cloudformation · Aug 1, 2024 · 8bd553d · 8bd553d
1 parent 70c71eb
commit 8bd553d
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Showing 2 changed files with 27 additions and 1 deletion.
diff --git a/src/cfnlint/jsonschema/_keywords_cfn.py b/src/cfnlint/jsonschema/_keywords_cfn.py
@@ -85,7 +85,7 @@ def validate(
 # Type checks
 #####
 def _raw_type(validator: Validator, tS: Any, instance: Any) -> bool:
-    if tS in ["object", "array"]:
+    if tS in ["object", "array", "null"] or validator.is_type(instance, "null"):
         return validator.is_type(instance, tS)
     if "string" == tS:
         if validator.is_type(instance, "object") or validator.is_type(

diff --git a/test/unit/module/jsonschema/test_keywords_cfn.py b/test/unit/module/jsonschema/test_keywords_cfn.py
@@ -101,6 +101,32 @@ def test_standard_values(self):
         self.build_execute_tests(True, ["string", "boolean"])
         self.build_execute_tests("true", ["string", "boolean"])
 
+    def test_null_values(self):
+        self.message_errors(
+            "Null value with string type",
+            None,
+            ["None is not of type 'string'"],
+            {"type": "string"},
+        )
+        self.message_errors(
+            "String value with null type",
+            "foo",
+            ["'foo' is not of type 'null'"],
+            {"type": "null"},
+        )
+        self.message_errors(
+            "Object value with null type",
+            {},
+            ["{} is not of type 'null'"],
+            {"type": "null"},
+        )
+        self.message_errors(
+            "None value with multiple types",
+            None,
+            [],
+            {"type": ["string", "null"]},
+        )
+
 
 class TestMultiCfnTypes(Base):
     def build_execute_tests(self, instance, supported_types, unsupported_type) -> None: