Exclude unset fields

src/graphql/execution/values.py

@@ -136,7 +136,7 @@ def on_input_value_error(
             )
 
         coerced_values[var_name] = coerce_input_value(
-            value, var_type, on_input_value_error
+            value, var_type, on_input_value_error, exclude_unset=schema.exclude_unset
         )
 
     return coerced_values

src/graphql/type/schema.py

@@ -140,6 +140,7 @@ def __init__(
         ast_node: Optional[ast.SchemaDefinitionNode] = None,
         extension_ast_nodes: Optional[Collection[ast.SchemaExtensionNode]] = None,
         assume_valid: bool = False,
+        exclude_unset: Optional[bool] = False
     ) -> None:
         """Initialize GraphQL schema.
 
@@ -202,6 +203,7 @@ def __init__(
         self.query_type = query
         self.mutation_type = mutation
         self.subscription_type = subscription
+        self.exclude_unset = exclude_unset
         # Provide specified directives (e.g. @include and @skip) by default
         self.directives = specified_directives if directives is None else directives
 
@@ -302,6 +304,7 @@ def to_kwargs(self) -> GraphQLSchemaKwargs:
             ast_node=self.ast_node,
             extension_ast_nodes=self.extension_ast_nodes,
             assume_valid=self._validation_errors is not None,
+            exclude_unset=self.exclude_unset,
         )
 
     def __copy__(self) -> "GraphQLSchema":  # pragma: no cover
@@ -339,6 +342,7 @@ def __deepcopy__(self, memo_: Dict) -> "GraphQLSchema":
             ast_node=deepcopy(self.ast_node),
             extension_ast_nodes=deepcopy(self.extension_ast_nodes),
             assume_valid=True,
+            exclude_unset=self.exclude_unset,
         )
 
     def get_root_type(self, operation: OperationType) -> Optional[GraphQLObjectType]:

src/graphql/utilities/coerce_input_value.py

@@ -44,6 +44,7 @@ def coerce_input_value(
     type_: GraphQLInputType,
     on_error: OnErrorCB = default_on_error,
     path: Optional[Path] = None,
+    exclude_unset: Optional[bool] = False,
 ) -> Any:
     """Coerce a Python value given a GraphQL Input Type."""
     if is_non_null_type(type_):
@@ -95,25 +96,31 @@ def coerce_input_value(
         for field_name, field in fields.items():
             field_value = input_value.get(field_name, Undefined)
 
-            if field_value is Undefined:
-                if field.default_value is not Undefined:
-                    # Use out name as name if it exists (extension of GraphQL.js).
-                    coerced_dict[field.out_name or field_name] = field.default_value
-                elif is_non_null_type(field.type):  # pragma: no cover else
-                    type_str = inspect(field.type)
-                    on_error(
-                        path.as_list() if path else [],
-                        input_value,
-                        GraphQLError(
-                            f"Field '{field_name}' of required type '{type_str}'"
-                            " was not provided."
-                        ),
+            if exclude_unset:
+                if field_name in input_value:
+                    coerced_dict[field.out_name or field_name] = coerce_input_value(
+                        field_value, field.type, on_error, Path(path, field_name, type_.name)
                     )
-                continue
-
-            coerced_dict[field.out_name or field_name] = coerce_input_value(
-                field_value, field.type, on_error, Path(path, field_name, type_.name)
-            )
+            else:
+                if field_value is Undefined:
+                    if field.default_value is not Undefined:
+                        # Use out name as name if it exists (extension of GraphQL.js).
+                        coerced_dict[field.out_name or field_name] = field.default_value
+                    elif is_non_null_type(field.type):  # pragma: no cover else
+                        type_str = inspect(field.type)
+                        on_error(
+                            path.as_list() if path else [],
+                            input_value,
+                            GraphQLError(
+                                f"Field '{field_name}' of required type '{type_str}'"
+                                " was not provided."
+                            ),
+                        )
+                    continue
+
+                coerced_dict[field.out_name or field_name] = coerce_input_value(
+                    field_value, field.type, on_error, Path(path, field_name, type_.name)
+                )
 
         # Ensure every provided field is defined.
         for field_name in input_value: