feat: support generating correct types for @oneOf input types

.changeset/wicked-geckos-do.md

@@ -0,0 +1,6 @@
+---
+'@graphql-codegen/visitor-plugin-common': minor
+'@graphql-codegen/typescript': minor
+---
+
+support the `@oneOf` directive on input types.

packages/plugins/other/visitor-plugin-common/src/base-types-visitor.ts

@@ -40,6 +40,7 @@ import {
   wrapWithSingleQuotes,
   getConfigValue,
   buildScalarsFromConfig,
+  isOneOfInputObjectType,
 } from './utils';
 import { OperationVariablesToObject } from './variables-to-object';
 import { parseEnumValues } from './enum-values';
@@ -453,9 +454,23 @@ export class BaseTypesVisitor<
       .withBlock(node.fields.join('\n'));
   }
 
+  getInputObjectOneOfDeclarationBlock(node: InputObjectTypeDefinitionNode): DeclarationBlock {
+    return new DeclarationBlock(this._declarationBlockConfig)
+      .export()
+      .asKind(this._parsedConfig.declarationKind.input)
+      .withName(this.convertName(node))
+      .withComment(node.description as any as string)
+      .withContent(`\n` + node.fields.join('\n  |'));
+  }
+
   InputObjectTypeDefinition(node: InputObjectTypeDefinitionNode): string {
     if (this.config.onlyEnums) return '';
 
+    // Why the heck is node.name a string and not { value: string } at runtime ?!
+    if (isOneOfInputObjectType(this._schema.getType(node.name as unknown as string))) {
+      return this.getInputObjectOneOfDeclarationBlock(node).string;
+    }
+
     return this.getInputObjectDeclarationBlock(node).string;
   }
 

packages/plugins/other/visitor-plugin-common/src/utils.ts

@@ -19,6 +19,8 @@ import {
   isListType,
   isAbstractType,
   GraphQLOutputType,
+  isInputObjectType,
+  GraphQLInputObjectType,
 } from 'graphql';
 import { ScalarsMap, NormalizedScalarsMap, ParsedScalarsMap } from './types';
 import { DEFAULT_SCALARS } from './scalars';
@@ -495,3 +497,26 @@ function clearOptional(str: string): string {
 function stripTrailingSpaces(str: string): string {
   return str.replace(/ +\n/g, '\n');
 }
+
+const isOneOfTypeCache = new WeakMap<GraphQLNamedType, boolean>();
+export function isOneOfInputObjectType(
+  namedType: GraphQLNamedType | null | undefined
+): namedType is GraphQLInputObjectType {
+  if (!namedType) {
+    return false;
+  }
+  let isOneOfType = isOneOfTypeCache.get(namedType);
+
+  if (isOneOfType !== undefined) {
+    return isOneOfType;
+  }
+
+  isOneOfType =
+    isInputObjectType(namedType) &&
+    ((namedType as unknown as Record<'isOneOf', boolean | undefined>).isOneOf ||
+      namedType.astNode?.directives?.some(d => d.name.value === 'oneOf'));
+
+  isOneOfTypeCache.set(namedType, isOneOfType);
+
+  return isOneOfType;
+}

packages/plugins/typescript/type-graphql/src/visitor.ts

@@ -415,12 +415,12 @@ export class TypeGraphQLVisitor<
     node: InputValueDefinitionNode,
     key?: number | string,
     parent?: any,
-    path?: any,
-    ancestors?: TypeDefinitionNode[]
+    path?: Array<string | number>,
+    ancestors?: Array<TypeDefinitionNode>
   ): string {
     const parentName = ancestors?.[ancestors.length - 1].name.value;
     if (parent && !this.hasTypeDecorators(parentName)) {
-      return this.typescriptVisitor.InputValueDefinition(node, key, parent);
+      return this.typescriptVisitor.InputValueDefinition(node, key, parent, path, ancestors);
     }
 
     const fieldDecorator = this.config.decoratorName.field;

packages/plugins/typescript/typescript/src/visitor.ts

@@ -9,6 +9,7 @@ import {
   DeclarationKind,
   normalizeAvoidOptionals,
   AvoidOptionalsConfig,
+  isOneOfInputObjectType,
 } from '@graphql-codegen/visitor-plugin-common';
 import { TypeScriptPluginConfig } from './config';
 import autoBind from 'auto-bind';
@@ -24,6 +25,7 @@ import {
   isEnumType,
   UnionTypeDefinitionNode,
   GraphQLObjectType,
+  TypeDefinitionNode,
 } from 'graphql';
 import { TypeScriptOperationVariablesToObject } from './typescript-variables-to-object';
 
@@ -280,8 +282,15 @@ export class TsVisitor<
     );
   }
 
-  InputValueDefinition(node: InputValueDefinitionNode, key?: number | string, parent?: any): string {
+  InputValueDefinition(
+    node: InputValueDefinitionNode,
+    key?: number | string,
+    parent?: any,
+    _path?: Array<string | number>,
+    ancestors?: Array<TypeDefinitionNode>
+  ): string {
     const originalFieldNode = parent[key] as FieldDefinitionNode;
+
     const addOptionalSign =
       !this.config.avoidOptionals.inputValue &&
       (originalFieldNode.type.kind !== Kind.NON_NULL_TYPE ||
@@ -294,14 +303,38 @@ export class TsVisitor<
       type = this._getDirectiveOverrideType(node.directives) || type;
     }
 
-    return (
-      comment +
-      indent(
-        `${this.config.immutableTypes ? 'readonly ' : ''}${node.name}${
-          addOptionalSign ? '?' : ''
-        }: ${type}${this.getPunctuation(declarationKind)}`
-      )
-    );
+    const readonlyPrefix = this.config.immutableTypes ? 'readonly ' : '';
+
+    const buildFieldDefinition = (isOneOf = false) => {
+      return `${readonlyPrefix}${node.name}${addOptionalSign && !isOneOf ? '?' : ''}: ${
+        isOneOf ? this.clearOptional(type) : type
+      }${this.getPunctuation(declarationKind)}`;
+    };
+
+    const realParentDef = ancestors?.[ancestors.length - 1];
+    if (realParentDef) {
+      const parentType = this._schema.getType(realParentDef.name.value);
+
+      if (isOneOfInputObjectType(parentType)) {
+        if (originalFieldNode.type.kind === Kind.NON_NULL_TYPE) {
+          throw new Error(
+            'Fields on an input object type can not be non-nullable. It seems like the schema was not validated.'
+          );
+        }
+        const fieldParts: Array<string> = [];
+        for (const fieldName of Object.keys(parentType.getFields())) {
+          // Why the heck is node.name a string and not { value: string } at runtime ?!
+          if (fieldName === (node.name as any as string)) {
+            fieldParts.push(buildFieldDefinition(true));
+            continue;
+          }
+          fieldParts.push(`${readonlyPrefix}${fieldName}?: never;`);
+        }
+        return comment + indent(`{ ${fieldParts.join(' ')} }`);
+      }
+    }
+
+    return comment + indent(buildFieldDefinition());
   }
 
   EnumTypeDefinition(node: EnumTypeDefinitionNode): string {

packages/plugins/typescript/typescript/tests/typescript.spec.ts

@@ -2536,6 +2536,130 @@ describe('TypeScript', () => {
       `);
       validateTs(result);
     });
+
+    describe('@oneOf on input types', () => {
+      const oneOfDirectiveDefinition = /* GraphQL */ `
+        directive @oneOf on INPUT_OBJECT
+      `;
+
+      it('correct output for type with single field', async () => {
+        const schema = buildSchema(
+          /* GraphQL */ `
+          input Input @oneOf {
+            int: Int
+          }
+
+          type Query {
+            foo(input: Input!): Boolean!
+          }
+        `.concat(oneOfDirectiveDefinition)
+        );
+
+        const result = await plugin(schema, [], {}, { outputFile: '' });
+
+        expect(result.content).toBeSimilarStringTo(`
+          export type Input =
+            { int: Scalars['Int']; };
+        `);
+      });
+
+      it('correct output for type with multiple fields', async () => {
+        const schema = buildSchema(
+          /* GraphQL */ `
+          input Input @oneOf {
+            int: Int
+            boolean: Boolean
+          }
+
+          type Query {
+            foo(input: Input!): Boolean!
+          }
+        `.concat(oneOfDirectiveDefinition)
+        );
+
+        const result = await plugin(schema, [], {}, { outputFile: '' });
+
+        expect(result.content).toBeSimilarStringTo(`
+          export type Input =
+            { int: Scalars['Int']; boolean?: never; }
+            | { int?: never; boolean: Scalars['Boolean']; };
+        `);
+      });
+
+      it('raises exception for type with non-optional fields', async () => {
+        const schema = buildSchema(
+          /* GraphQL */ `
+          input Input @oneOf {
+            int: Int!
+            boolean: Boolean!
+          }
+
+          type Query {
+            foo(input: Input!): Boolean!
+          }
+        `.concat(oneOfDirectiveDefinition)
+        );
+
+        try {
+          await plugin(schema, [], {}, { outputFile: '' });
+          throw new Error('Plugin should have raised an exception.');
+        } catch (err) {
+          expect(err.message).toEqual(
+            'Fields on an input object type can not be non-nullable. It seems like the schema was not validated.'
+          );
+        }
+      });
+
+      it('handles extensions properly', async () => {
+        const schema = buildSchema(
+          /* GraphQL */ `
+          input Input @oneOf {
+            int: Int
+          }
+
+          extend input Input {
+            boolean: Boolean
+          }
+
+          type Query {
+            foo(input: Input!): Boolean!
+          }
+        `.concat(oneOfDirectiveDefinition)
+        );
+
+        const result = await plugin(schema, [], {}, { outputFile: '' });
+        expect(result.content).toBeSimilarStringTo(`
+          export type Input =
+            { int: Scalars['Int']; boolean?: never; }
+            | { int?: never; boolean: Scalars['Boolean']; };
+        `);
+      });
+
+      it('handles .isOneOf property on input object types properly', async () => {
+        const schema = buildSchema(
+          /* GraphQL */ `
+          input Input {
+            int: Int
+            boolean: Boolean
+          }
+
+          type Query {
+            foo(input: Input!): Boolean!
+          }
+        `.concat(oneOfDirectiveDefinition)
+        );
+
+        const inputType: Record<'isOneOf', boolean> = schema.getType('Input') as any;
+        inputType.isOneOf = true;
+
+        const result = await plugin(schema, [], {}, { outputFile: '' });
+        expect(result.content).toBeSimilarStringTo(`
+          export type Input =
+            { int: Scalars['Int']; boolean?: never; }
+            | { int?: never; boolean: Scalars['Boolean']; };
+        `);
+      });
+    });
   });
 
   describe('Naming Convention & Types Prefix', () => {