test_ast_from_value: improve coverage

Also fix porting bug revealed in added test.

Replicates graphql/graphql-js@34c5580

Author: Cito

src/graphql/utilities/ast_from_value.py

@@ -1,5 +1,5 @@
 import re
-from typing import Any, Iterable, List, Mapping, Optional, cast
+from typing import Any, Iterable, Mapping, Optional, cast
 
 from ..language import (
     BooleanValueNode,
@@ -14,7 +14,7 @@
     StringValueNode,
     ValueNode,
 )
-from ..pyutils import inspect, is_nullish, is_invalid
+from ..pyutils import FrozenList, inspect, is_nullish, is_invalid
 from ..type import (
     GraphQLID,
     GraphQLInputType,
@@ -71,8 +71,9 @@ def ast_from_value(value: Any, type_: GraphQLInputType) -> Optional[ValueNode]:
         type_ = cast(GraphQLList, type_)
         item_type = type_.of_type
         if isinstance(value, Iterable) and not isinstance(value, str):
-            value_nodes = [ast_from_value(item, item_type) for item in value]
-            return ListValueNode(values=value_nodes)
+            maybe_value_nodes = (ast_from_value(item, item_type) for item in value)
+            value_nodes = filter(None, maybe_value_nodes)
+            return ListValueNode(values=FrozenList(value_nodes))
         return ast_from_value(value, item_type)
 
     # Populate the fields of the input object by creating ASTs from each value in the
@@ -81,18 +82,17 @@ def ast_from_value(value: Any, type_: GraphQLInputType) -> Optional[ValueNode]:
         if value is None or not isinstance(value, Mapping):
             return None
         type_ = cast(GraphQLInputObjectType, type_)
-        field_nodes: List[ObjectFieldNode] = []
-        append_node = field_nodes.append
-        for field_name, field in type_.fields.items():
-            if field_name in value:
-                field_value = ast_from_value(value[field_name], field.type)
-                if field_value:
-                    append_node(
-                        ObjectFieldNode(
-                            name=NameNode(value=field_name), value=field_value
-                        )
-                    )
-        return ObjectValueNode(fields=field_nodes)
+        field_items = (
+            (field_name, ast_from_value(value[field_name], field.type))
+            for field_name, field in type_.fields.items()
+            if field_name in value
+        )
+        field_nodes = (
+            ObjectFieldNode(name=NameNode(value=field_name), value=field_value)
+            for field_name, field_value in field_items
+            if field_value
+        )
+        return ObjectValueNode(fields=FrozenList(field_nodes))
 
     if is_leaf_type(type_):
         # Since value is an internally represented value, it must be serialized to an

tests/utilities/test_ast_from_value.py

@@ -25,6 +25,7 @@
     GraphQLInt,
     GraphQLList,
     GraphQLNonNull,
+    GraphQLScalarType,
     GraphQLString,
 )
 from graphql.utilities import ast_from_value
@@ -123,6 +124,33 @@ def converts_id_values_to_int_or_string_asts():
 
         assert ast_from_value(INVALID, GraphQLString) is None
 
+    def converts_using_serialize_from_a_custom_scalar_type():
+        pass_through_scalar = GraphQLScalarType(
+            "PassThroughScalar", serialize=lambda value: value,
+        )
+
+        assert ast_from_value("value", pass_through_scalar) == StringValueNode(
+            value="value"
+        )
+
+        return_null_scalar = GraphQLScalarType(
+            "ReturnNullScalar", serialize=lambda value: None,
+        )
+
+        assert ast_from_value("value", return_null_scalar) is None
+
+        class SomeClass:
+            pass
+
+        return_custom_class_scalar = GraphQLScalarType(
+            "ReturnCustomClassScalar", serialize=lambda value: SomeClass(),
+        )
+
+        with raises(TypeError) as exc_info:
+            ast_from_value("value", return_custom_class_scalar)
+        msg = str(exc_info.value)
+        assert msg == "Cannot convert value to AST: <SomeClass instance>"
+
     def does_not_convert_non_null_values_to_null_value():
         non_null_boolean = GraphQLNonNull(GraphQLBoolean)
         assert ast_from_value(None, non_null_boolean) is None
@@ -162,12 +190,21 @@ def converts_list_singletons():
             value="FOO"
         )
 
-    def converts_input_objects():
-        input_obj = GraphQLInputObjectType(
-            "MyInputObj",
-            {"foo": GraphQLInputField(GraphQLFloat), "bar": GraphQLInputField(my_enum)},
+    def skips_invalid_list_items():
+        ast = ast_from_value(
+            ["FOO", None, "BAR"], GraphQLList(GraphQLNonNull(GraphQLString))
+        )
+
+        assert ast == ListValueNode(
+            values=[StringValueNode(value="FOO"), StringValueNode(value="BAR")]
         )
 
+    input_obj = GraphQLInputObjectType(
+        "MyInputObj",
+        {"foo": GraphQLInputField(GraphQLFloat), "bar": GraphQLInputField(my_enum)},
+    )
+
+    def converts_input_objects():
         assert ast_from_value({"foo": 3, "bar": "HELLO"}, input_obj) == ObjectValueNode(
             fields=[
                 ObjectFieldNode(
@@ -180,11 +217,6 @@ def converts_input_objects():
         )
 
     def converts_input_objects_with_explicit_nulls():
-        input_obj = GraphQLInputObjectType(
-            "MyInputObj",
-            {"foo": GraphQLInputField(GraphQLFloat), "bar": GraphQLInputField(my_enum)},
-        )
-
         assert ast_from_value({"foo": None}, input_obj) == ObjectValueNode(
             fields=[ObjectFieldNode(name=NameNode(value="foo"), value=NullValueNode())]
         )