feat: consolidate matching input and output types into single generated class

src/definitions/input.ts

@@ -17,6 +17,7 @@ import { buildTypeMetadata } from "../helpers/build-type-metadata";
 import { buildAnnotations } from "../helpers/build-annotations";
 import { indent } from "@graphql-codegen/visitor-plugin-common";
 import { CodegenConfigWithDefaults } from "../helpers/build-config-with-defaults";
+import { inputTypeHasMatchingOutputType } from "../helpers/input-type-has-matching-output-type";
 
 export function buildInputObjectDefinition(
   node: InputObjectTypeDefinitionNode,
@@ -27,6 +28,11 @@ export function buildInputObjectDefinition(
     return "";
   }
 
+  const typeWillBeConsolidated = inputTypeHasMatchingOutputType(node, schema);
+  if (typeWillBeConsolidated) {
+    return "";
+  }
+
   const classMembers = (node.fields ?? [])
     .map((arg) => {
       const typeToUse = buildTypeMetadata(arg.type, schema, config);

src/helpers/input-type-has-matching-output-type.ts

@@ -0,0 +1,52 @@
+import { Kind, TypeNode } from "graphql/index";
+import { GraphQLSchema, InputObjectTypeDefinitionNode } from "graphql";
+
+export function inputTypeHasMatchingOutputType(
+  inputTypeNode: InputObjectTypeDefinitionNode,
+  schema: GraphQLSchema,
+) {
+  const typeNameWithoutInput = getTypeNameWithoutInput(
+    inputTypeNode.name.value,
+  );
+  const matchingType = schema.getType(typeNameWithoutInput)?.astNode;
+  const matchingTypeFields =
+    matchingType?.kind === Kind.OBJECT_TYPE_DEFINITION
+      ? matchingType.fields
+      : [];
+  const inputFields = inputTypeNode.fields;
+  const fieldsMatch = matchingTypeFields?.every((field) => {
+    const matchingInputField = inputFields?.find(
+      (inputField) => inputField.name.value === field.name.value,
+    );
+    if (!matchingInputField) return false;
+    return fieldsAreEquivalent(field.type, matchingInputField.type);
+  });
+  return Boolean(matchingTypeFields?.length && fieldsMatch);
+}
+
+function getTypeNameWithoutInput(name: string) {
+  return name.endsWith("Input") ? name.replace("Input", "") : name;
+}
+
+function fieldsAreEquivalent(
+  typeField: TypeNode,
+  inputField: TypeNode,
+): boolean {
+  switch (typeField.kind) {
+    case Kind.NAMED_TYPE:
+      return (
+        inputField.kind === Kind.NAMED_TYPE &&
+        typeField.name.value === getTypeNameWithoutInput(inputField.name.value)
+      );
+    case Kind.LIST_TYPE:
+      return (
+        inputField.kind === Kind.LIST_TYPE &&
+        fieldsAreEquivalent(typeField.type, inputField.type)
+      );
+    case Kind.NON_NULL_TYPE:
+      return (
+        inputField.kind === Kind.NON_NULL_TYPE &&
+        fieldsAreEquivalent(typeField.type, inputField.type)
+      );
+  }
+}

test/unit/should_consolidate_input_and_output_types/expected.kt

@@ -0,0 +1,53 @@
+package com.kotlin.generated
+
+import com.expediagroup.graphql.generator.annotations.*
+
+data class MyTypeToConsolidate(
+    val field: List<String>? = null,
+    val field2: NestedTypeToConsolidate? = null
+)
+
+data class NestedTypeToConsolidate(
+    val field: String? = null
+)
+
+@GraphQLDescription("A description for MyTypeToConsolidate2")
+data class MyTypeToConsolidate2(
+    val field: String? = null
+)
+
+data class MyTypeToConsolidate3(
+    val field: String? = null
+)
+
+@GraphQLDescription("It always uses the type description when consolidating")
+data class MyTypeToConsolidate4(
+    val field: String? = null
+)
+
+data class MyTypeNotToConsolidate(
+    val field: String? = null
+)
+
+@GraphQLDescription("The type name must exactly match in order to consolidate")
+data class MyTypeToNotConsolidateInput(
+    val field: String? = null
+)
+
+data class MyTypeToNotConsolidate2(
+    val field: String? = null
+)
+
+data class MyTypeInputToNotConsolidate2(
+    val field: String? = null
+)
+
+data class MyTypeWhereFieldsDoNotMatch(
+    val field: String? = null,
+    val field2: String? = null
+)
+
+data class MyTypeWhereFieldsDoNotMatchInput(
+    val field: String? = null,
+    val field2: Int? = null
+)

test/unit/should_consolidate_input_and_output_types/schema.graphql

@@ -0,0 +1,86 @@
+# typical case where input and output types are consolidated
+
+type MyTypeToConsolidate {
+  field: [String!]
+  field2: NestedTypeToConsolidate
+}
+
+input MyTypeToConsolidateInput {
+  field: [String!]
+  field2: NestedTypeToConsolidateInput
+}
+
+type NestedTypeToConsolidate {
+  field: String
+}
+
+input NestedTypeToConsolidateInput {
+  field: String
+}
+
+# case where type has description but input does not
+
+"A description for MyTypeToConsolidate2"
+type MyTypeToConsolidate2 {
+  field: String
+}
+
+input MyTypeToConsolidate2Input {
+  field: String
+}
+
+# case where input has description but type does not
+
+type MyTypeToConsolidate3 {
+  field: String
+}
+
+"It ignores the description on the input when consolidating"
+input MyTypeToConsolidate3Input {
+  field: String
+}
+
+# case where both type and input have descriptions
+
+"It always uses the type description when consolidating"
+type MyTypeToConsolidate4 {
+  field: String
+}
+
+"A description for MyTypeToConsolidateInput4"
+input MyTypeToConsolidate4Input {
+  field: String
+}
+
+# case where type and input names do not match
+
+type MyTypeNotToConsolidate {
+  field: String
+}
+
+"The type name must exactly match in order to consolidate"
+input MyTypeToNotConsolidateInput {
+  field: String
+}
+
+# case where type has input in the middle of the name
+
+type MyTypeToNotConsolidate2 {
+  field: String
+}
+
+input MyTypeInputToNotConsolidate2 {
+  field: String
+}
+
+# case where type and input names match but fields do not match
+
+type MyTypeWhereFieldsDoNotMatch {
+  field: String
+  field2: String
+}
+
+input MyTypeWhereFieldsDoNotMatchInput {
+  field: String
+  field2: Int
+}