Added 'GraphQLSchema.getRootType' and deprecate getOperationRootType

src/execution/__tests__/executor-test.ts

@@ -908,6 +908,29 @@ describe('Execute: Handles basic execution tasks', () => {
     expect(result).to.deep.equal({ data: { a: 'b' } });
   });
 
+  it('resolves to an error if schema does not support operation', () => {
+    const schema = new GraphQLSchema({ assumeValid: true });
+
+    const document = parse(`
+      query Q { __typename }
+      mutation M { __typename }
+      subscription S { __typename }
+    `);
+
+    // FIXME: errors should be wrapped into ExecutionResult
+    expect(() =>
+      executeSync({ schema, document, operationName: 'Q' }),
+    ).to.throw('Schema is not configured to execute query operation.');
+
+    expect(() =>
+      executeSync({ schema, document, operationName: 'M' }),
+    ).to.throw('Schema is not configured to execute mutation operation.');
+
+    expect(() =>
+      executeSync({ schema, document, operationName: 'S' }),
+    ).to.throw('Schema is not configured to execute subscription operation.');
+  });
+
   it('correct field ordering despite execution order', async () => {
     const schema = new GraphQLSchema({
       query: new GraphQLObjectType({

src/execution/__tests__/subscribe-test.ts

@@ -367,6 +367,22 @@ describe('Subscription Initialization Phase', () => {
     );
   });
 
+  it('resolves to an error if schema does not support subscriptions', async () => {
+    const schema = new GraphQLSchema({ query: DummyQueryType });
+    const document = parse('subscription { unknownField }');
+
+    const result = await subscribe({ schema, document });
+    expectJSON(result).to.deep.equal({
+      errors: [
+        {
+          message:
+            'Schema is not configured to execute subscription operation.',
+          locations: [{ line: 1, column: 1 }],
+        },
+      ],
+    });
+  });
+
   it('resolves to an error for unknown subscription field', async () => {
     const schema = new GraphQLSchema({
       query: DummyQueryType,

src/execution/execute.ts

@@ -51,8 +51,6 @@ import {
   isNonNullType,
 } from '../type/definition';
 
-import { getOperationRootType } from '../utilities/getOperationRootType';
-
 import { getVariableValues, getArgumentValues } from './values';
 import {
   collectFields,
@@ -336,12 +334,19 @@ function executeOperation(
   operation: OperationDefinitionNode,
   rootValue: unknown,
 ): PromiseOrValue<ObjMap<unknown> | null> {
-  const type = getOperationRootType(exeContext.schema, operation);
-  const fields = collectFields(
+  const rootType = exeContext.schema.getRootType(operation.operation);
+  if (rootType == null) {
+    throw new GraphQLError(
+      `Schema is not configured to execute ${operation.operation} operation.`,
+      operation,
+    );
+  }
+
+  const rootFields = collectFields(
     exeContext.schema,
     exeContext.fragments,
     exeContext.variableValues,
-    type,
+    rootType,
     operation.selectionSet,
   );
 
@@ -353,8 +358,14 @@ function executeOperation(
   try {
     const result =
       operation.operation === 'mutation'
-        ? executeFieldsSerially(exeContext, type, rootValue, path, fields)
-        : executeFields(exeContext, type, rootValue, path, fields);
+        ? executeFieldsSerially(
+            exeContext,
+            rootType,
+            rootValue,
+            path,
+            rootFields,
+          )
+        : executeFields(exeContext, rootType, rootValue, path, rootFields);
     if (isPromise(result)) {
       return result.then(undefined, (error) => {
         exeContext.errors.push(error);

src/execution/subscribe.ts

@@ -11,8 +11,6 @@ import type { DocumentNode } from '../language/ast';
 import type { GraphQLSchema } from '../type/schema';
 import type { GraphQLFieldResolver } from '../type/definition';
 
-import { getOperationRootType } from '../utilities/getOperationRootType';
-
 import type {
   ExecutionArgs,
   ExecutionResult,
@@ -194,16 +192,24 @@ async function executeSubscription(
 ): Promise<unknown> {
   const { schema, fragments, operation, variableValues, rootValue } =
     exeContext;
-  const type = getOperationRootType(schema, operation);
-  const fields = collectFields(
+
+  const rootType = schema.getSubscriptionType();
+  if (rootType == null) {
+    throw new GraphQLError(
+      'Schema is not configured to execute subscription operation.',
+      operation,
+    );
+  }
+
+  const rootFields = collectFields(
     schema,
     fragments,
     variableValues,
-    type,
+    rootType,
     operation.selectionSet,
   );
-  const [responseName, fieldNodes] = [...fields.entries()][0];
-  const fieldDef = getFieldDef(schema, type, fieldNodes[0]);
+  const [responseName, fieldNodes] = [...rootFields.entries()][0];
+  const fieldDef = getFieldDef(schema, rootType, fieldNodes[0]);
 
   if (!fieldDef) {
     const fieldName = fieldNodes[0].name.value;
@@ -213,8 +219,14 @@ async function executeSubscription(
     );
   }
 
-  const path = addPath(undefined, responseName, type.name);
-  const info = buildResolveInfo(exeContext, fieldDef, fieldNodes, type, path);
+  const path = addPath(undefined, responseName, rootType.name);
+  const info = buildResolveInfo(
+    exeContext,
+    fieldDef,
+    fieldNodes,
+    rootType,
+    path,
+  );
 
   try {
     // Implements the "ResolveFieldEventStream" algorithm from GraphQL specification.

src/type/schema.ts

@@ -9,6 +9,7 @@ import type { Maybe } from '../jsutils/Maybe';
 import type { GraphQLError } from '../error/GraphQLError';
 
 import type {
+  OperationTypeNode,
   SchemaDefinitionNode,
   SchemaExtensionNode,
 } from '../language/ast';
@@ -275,6 +276,17 @@ export class GraphQLSchema {
     return this._subscriptionType;
   }
 
+  getRootType(operation: OperationTypeNode): Maybe<GraphQLObjectType> {
+    switch (operation) {
+      case 'query':
+        return this.getQueryType();
+      case 'mutation':
+        return this.getMutationType();
+      case 'subscription':
+        return this.getSubscriptionType();
+    }
+  }
+
   getTypeMap(): TypeMap {
     return this._typeMap;
   }

src/utilities/TypeInfo.ts

@@ -169,19 +169,8 @@ export class TypeInfo {
         this._directive = schema.getDirective(node.name.value);
         break;
       case Kind.OPERATION_DEFINITION: {
-        let type: unknown;
-        switch (node.operation) {
-          case 'query':
-            type = schema.getQueryType();
-            break;
-          case 'mutation':
-            type = schema.getMutationType();
-            break;
-          case 'subscription':
-            type = schema.getSubscriptionType();
-            break;
-        }
-        this._typeStack.push(isObjectType(type) ? type : undefined);
+        const rootType = schema.getRootType(node.operation);
+        this._typeStack.push(isObjectType(rootType) ? rootType : undefined);
         break;
       }
       case Kind.INLINE_FRAGMENT:

src/utilities/__tests__/getOperationRootType-test.ts

@@ -40,7 +40,7 @@ function getOperationNode(doc: DocumentNode): OperationDefinitionNode {
   return operationNode;
 }
 
-describe('getOperationRootType', () => {
+describe('Deprecated - getOperationRootType', () => {
   it('Gets a Query type for an unnamed OperationDefinitionNode', () => {
     const testSchema = new GraphQLSchema({
       query: queryType,

src/utilities/getOperationRootType.ts

@@ -10,6 +10,8 @@ import type { GraphQLObjectType } from '../type/definition';
 
 /**
  * Extracts the root type of the operation from the schema.
+ *
+ * @deprecated Please use `GraphQLSchema.getRootType` instead. Will be removed in v17
  */
 export function getOperationRootType(
   schema: GraphQLSchema,