add tests and docs for disable introspection rule

docs/execution/queryvalidation.rst

@@ -16,7 +16,7 @@ queries. It takes in the following arguments.
 - ``ignore`` Stops recursive depth checking based on a field name. Either a string or regexp to match the name, or a function that returns a boolean
 - ``callback`` Called each time validation runs. Receives an Object which is a map of the depths for each operation.
 
-Example
+Usage
 -------
 
 Here is how you would implement depth-limiting on your schema.
@@ -33,7 +33,7 @@ Here is how you would implement depth-limiting on your schema.
 
     schema = Schema(query=MyQuery)
 
-    # Queries which have a depth more than 20
+    # queries which have a depth more than 20
     # will not be executed.
 
     validation_errors = validate(
@@ -47,6 +47,39 @@ Here is how you would implement depth-limiting on your schema.
     )
 
 
+Disable Introspection
+---------------------
+the disable introspection validation rule ensures that your schema cannot be introspected.
+This is a useful security measure in production environments.
+
+Usage
+-------
+
+Here is how you would disable introspection for your schema.
+
+.. code:: python
+    from graphql import validate, parse
+    from graphene import ObjectType, Schema, String
+    from graphene.validation import DisableIntrospection
+
+
+    class MyQuery(ObjectType):
+        name = String(required=True)
+
+
+    schema = Schema(query=MyQuery)
+
+    # introspection queries will not be executed.
+
+    validation_errors = validate(
+        schema=schema,
+        document_ast=parse('THE QUERY'),
+        rules=(
+            DisableIntrospection,
+        )
+    )
+
+
 Implementing custom validators
 ------------------------------
 All custom query validators should extend the `ValidationRule <https://github.com/graphql-python/graphql-core/blob/v3.0.5/src/graphql/validation/rules/__init__.py#L37>`_
@@ -56,7 +89,7 @@ perform validation, your validator class should define one or more of enter_* an
 enter/leave items as well as details on function documentation, please see contents of the visitor module. To make
 validation fail, you should call validator's report_error method with the instance of GraphQLError describing failure
 reason. Here is an example query validator that visits field definitions in GraphQL query and fails query validation
-if any of those fields are blacklisted fields:
+if any of those fields are blacklisted:
 
 .. code:: python
     from graphql import GraphQLError
@@ -70,7 +103,7 @@ if any of those fields are blacklisted fields:
 
 
     def is_blacklisted_field(field_name: str):
-        return key.lower() in my_blacklist
+        return field_name.lower() in my_blacklist
 
 
     class BlackListRule(ValidationRule):

graphene/validation/__init__.py

@@ -1,8 +1,8 @@
 from .depth_limit import depth_limit_validator
-from .disable_introspection import disable_introspection
+from .disable_introspection import DisableIntrospection
 
 
 __all__ = [
-    "depth_limit_validator",
+    "DisableIntrospection",
-    "disable_introspection"
+    "depth_limit_validator"
 ]

graphene/validation/depth_limit.py

@@ -116,7 +116,7 @@ def determine_depth(
     if depth_so_far > max_depth:
         context.report_error(
             GraphQLError(
-                f"'{operation_name}' exceeds maximum operation depth of {max_depth}",
+                f"'{operation_name}' exceeds maximum operation depth of {max_depth}.",
                 [node],
             )
         )
@@ -172,7 +172,7 @@ def determine_depth(
             )
         )
     else:
-        raise Exception(f"Depth crawler cannot handle: {node.kind}")  # pragma: no cover
+        raise Exception(f"Depth crawler cannot handle: {node.kind}.")  # pragma: no cover
 
 
 def is_ignored(node: FieldNode, ignore: Optional[List[IgnoreType]] = None) -> bool:
@@ -191,6 +191,6 @@ def is_ignored(node: FieldNode, ignore: Optional[List[IgnoreType]] = None) -> bo
             if rule(field_name):
                 return True
         else:
-            raise ValueError(f"Invalid ignore option: {rule}")
+            raise ValueError(f"Invalid ignore option: {rule}.")
 
     return False

graphene/validation/disable_introspection.py

@@ -5,8 +5,7 @@ from graphql.validation import ValidationRule
 from ..utils.is_introspection_key import is_introspection_key
 
 
-def disable_introspection():
+class DisableIntrospection(ValidationRule):
-    class DisableIntrospection(ValidationRule):
     def enter_field(self, node: FieldNode, *_args):
         field_name = node.name.value
         if not is_introspection_key(field_name):
@@ -18,5 +17,3 @@ def disable_introspection():
                 node,
             )
         )
-
-    return DisableIntrospection

graphene/validation/tests/test_depth_limit_validator.py

@@ -235,7 +235,7 @@ def test_should_catch_very_deep_query():
     errors, result = run_query(query, 4)
 
     assert len(errors) == 1
-    assert errors[0].message == "'anonymous' exceeds maximum operation depth of 4"
+    assert errors[0].message == "'anonymous' exceeds maximum operation depth of 4."
 
 
 def test_should_ignore_field():

graphene/validation/tests/test_disable_introspection.py

@@ -1,7 +1,7 @@
 from graphql import parse, validate
 
 from ...types import Schema, ObjectType, String
-from ..disable_introspection import disable_introspection
+from ..disable_introspection import DisableIntrospection
 
 
 class Query(ObjectType):
@@ -9,6 +9,10 @@ class Query(ObjectType):
         required=True
     )
 
+    @staticmethod
+    def resolve_name(root, info):
+        return "Hello world!"
+
 
 schema = Schema(query=Query)
 
@@ -16,14 +20,24 @@ schema = Schema(query=Query)
 def run_query(query: str):
     document = parse(query)
 
-    result = None
-
     errors = validate(
         schema=schema.graphql_schema,
         document_ast=document,
         rules=(
-            disable_introspection(),
+            DisableIntrospection,
         ),
     )
 
-    return errors, result
+    return errors
+
+
+def test_disallows_introspection_queries():
+    errors = run_query("{ __schema { queryType { name } } }")
+
+    assert len(errors) == 1
+    assert errors[0].message == "Cannot query '__schema': introspection is disabled."
+
+
+def test_allows_non_introspection_queries():
+    errors = run_query("{ name }")
+    assert len(errors) == 0