Implement onError proposal (but with ErrorBehavior rather than __ErrorBehavior)

src/__tests__/starWarsIntrospection-test.ts

@@ -37,6 +37,7 @@ describe('Star Wars Introspection Tests', () => {
             { name: 'Droid' },
             { name: 'Query' },
             { name: 'Boolean' },
+            { name: 'ErrorBehavior' },
             { name: '__Schema' },
             { name: '__Type' },
             { name: '__TypeKind' },

src/error/ErrorBehavior.ts

@@ -0,0 +1,7 @@
+export type ErrorBehavior = 'NO_PROPAGATE' | 'PROPAGATE' | 'ABORT';
+
+export function isErrorBehavior(onError: unknown): onError is ErrorBehavior {
+  return (
+    onError === 'NO_PROPAGATE' || onError === 'PROPAGATE' || onError === 'ABORT'
+  );
+}

src/error/index.ts

@@ -9,3 +9,4 @@ export type {
 export { syntaxError } from './syntaxError';
 
 export { locatedError } from './locatedError';
+export type { ErrorBehavior } from './ErrorBehavior';

src/execution/__tests__/executor-test.ts

@@ -264,6 +264,7 @@ describe('Execute: Handles basic execution tasks', () => {
       'rootValue',
       'operation',
       'variableValues',
+      'errorBehavior',
     );
 
     const operation = document.definitions[0];
@@ -276,6 +277,7 @@ describe('Execute: Handles basic execution tasks', () => {
       schema,
       rootValue,
       operation,
+      errorBehavior: 'PROPAGATE',
     });
 
     const field = operation.selectionSet.selections[0];
@@ -286,6 +288,70 @@ describe('Execute: Handles basic execution tasks', () => {
     });
   });
 
+  it('reflects onError:NO_PROPAGATE via errorBehavior', () => {
+    let resolvedInfo;
+    const testType = new GraphQLObjectType({
+      name: 'Test',
+      fields: {
+        test: {
+          type: GraphQLString,
+          resolve(_val, _args, _ctx, info) {
+            resolvedInfo = info;
+          },
+        },
+      },
+    });
+    const schema = new GraphQLSchema({ query: testType });
+
+    const document = parse('query ($var: String) { result: test }');
+    const rootValue = { root: 'val' };
+    const variableValues = { var: 'abc' };
+
+    executeSync({
+      schema,
+      document,
+      rootValue,
+      variableValues,
+      onError: 'NO_PROPAGATE',
+    });
+
+    expect(resolvedInfo).to.include({
+      errorBehavior: 'NO_PROPAGATE',
+    });
+  });
+
+  it('reflects onError:ABORT via errorBehavior', () => {
+    let resolvedInfo;
+    const testType = new GraphQLObjectType({
+      name: 'Test',
+      fields: {
+        test: {
+          type: GraphQLString,
+          resolve(_val, _args, _ctx, info) {
+            resolvedInfo = info;
+          },
+        },
+      },
+    });
+    const schema = new GraphQLSchema({ query: testType });
+
+    const document = parse('query ($var: String) { result: test }');
+    const rootValue = { root: 'val' };
+    const variableValues = { var: 'abc' };
+
+    executeSync({
+      schema,
+      document,
+      rootValue,
+      variableValues,
+      onError: 'ABORT',
+    });
+
+    expect(resolvedInfo).to.include({
+      errorBehavior: 'ABORT',
+    });
+  });
+
   it('populates path correctly with complex types', () => {
     let path;
     const someObject = new GraphQLObjectType({
@@ -740,6 +806,163 @@ describe('Execute: Handles basic execution tasks', () => {
     });
   });
 
+  it('Full response path is included for non-nullable fields with onError:NO_PROPAGATE', () => {
+    const A: GraphQLObjectType = new GraphQLObjectType({
+      name: 'A',
+      fields: () => ({
+        nullableA: {
+          type: A,
+          resolve: () => ({}),
+        },
+        nonNullA: {
+          type: new GraphQLNonNull(A),
+          resolve: () => ({}),
+        },
+        throws: {
+          type: new GraphQLNonNull(GraphQLString),
+          resolve: () => {
+            throw new Error('Catch me if you can');
+          },
+        },
+      }),
+    });
+    const schema = new GraphQLSchema({
+      query: new GraphQLObjectType({
+        name: 'query',
+        fields: () => ({
+          nullableA: {
+            type: A,
+            resolve: () => ({}),
+          },
+        }),
+      }),
+    });
+
+    const document = parse(`
+      query {
+        nullableA {
+          aliasedA: nullableA {
+            nonNullA {
+              anotherA: nonNullA {
+                throws
+              }
+            }
+          }
+        }
+      }
+    `);
+
+    const result = executeSync({ schema, document, onError: 'NO_PROPAGATE' });
+    expectJSON(result).toDeepEqual({
+      data: {
+        nullableA: {
+          aliasedA: {
+            nonNullA: {
+              anotherA: {
+                throws: null,
+              },
+            },
+          },
+        },
+      },
+      errors: [
+        {
+          message: 'Catch me if you can',
+          locations: [{ line: 7, column: 17 }],
+          path: ['nullableA', 'aliasedA', 'nonNullA', 'anotherA', 'throws'],
+        },
+      ],
+    });
+  });
+
+  it('Full response path is included for non-nullable fields with onError:ABORT', () => {
+    const A: GraphQLObjectType = new GraphQLObjectType({
+      name: 'A',
+      fields: () => ({
+        nullableA: {
+          type: A,
+          resolve: () => ({}),
+        },
+        nonNullA: {
+          type: new GraphQLNonNull(A),
+          resolve: () => ({}),
+        },
+        throws: {
+          type: new GraphQLNonNull(GraphQLString),
+          resolve: () => {
+            throw new Error('Catch me if you can');
+          },
+        },
+      }),
+    });
+    const schema = new GraphQLSchema({
+      query: new GraphQLObjectType({
+        name: 'query',
+        fields: () => ({
+          nullableA: {
+            type: A,
+            resolve: () => ({}),
+          },
+        }),
+      }),
+    });
+
+    const document = parse(`
+      query {
+        nullableA {
+          aliasedA: nullableA {
+            nonNullA {
+              anotherA: nonNullA {
+                throws
+              }
+            }
+          }
+        }
+      }
+    `);
+
+    const result = executeSync({ schema, document, onError: 'ABORT' });
+    expectJSON(result).toDeepEqual({
+      data: null,
+      errors: [
+        {
+          message: 'Catch me if you can',
+          locations: [{ line: 7, column: 17 }],
+          path: ['nullableA', 'aliasedA', 'nonNullA', 'anotherA', 'throws'],
+        },
+      ],
+    });
+  });
+
+  it('raises request error with invalid onError', () => {
+    const schema = new GraphQLSchema({
+      query: new GraphQLObjectType({
+        name: 'query',
+        fields: () => ({
+          a: {
+            type: GraphQLInt,
+          },
+        }),
+      }),
+    });
+
+    const document = parse('{ a }');
+    const result = executeSync({
+      schema,
+      document,
+      // @ts-expect-error
+      onError: 'DANCE',
+    });
+    expectJSON(result).toDeepEqual({
+      errors: [
+        {
+          message:
+            'Unsupported `onError` value; supported values are `NO_PROPAGATE`, `PROPAGATE` and `ABORT`.',
+        },
+      ],
+    });
+  });
+
   it('uses the inline operation if no operation name is provided', () => {
     const schema = new GraphQLSchema({
       query: new GraphQLObjectType({

src/execution/execute.ts

@@ -13,6 +13,8 @@ import { promiseForObject } from '../jsutils/promiseForObject';
 import type { PromiseOrValue } from '../jsutils/PromiseOrValue';
 import { promiseReduce } from '../jsutils/promiseReduce';
 
+import type { ErrorBehavior } from '../error/ErrorBehavior';
+import { isErrorBehavior } from '../error/ErrorBehavior';
 import type { GraphQLFormattedError } from '../error/GraphQLError';
 import { GraphQLError } from '../error/GraphQLError';
 import { locatedError } from '../error/locatedError';
@@ -115,6 +117,7 @@ export interface ExecutionContext {
   typeResolver: GraphQLTypeResolver<any, any>;
   subscribeFieldResolver: GraphQLFieldResolver<any, any>;
   errors: Array<GraphQLError>;
+  errorBehavior: ErrorBehavior;
 }
 
 /**
@@ -152,6 +155,15 @@ export interface ExecutionArgs {
   fieldResolver?: Maybe<GraphQLFieldResolver<any, any>>;
   typeResolver?: Maybe<GraphQLTypeResolver<any, any>>;
   subscribeFieldResolver?: Maybe<GraphQLFieldResolver<any, any>>;
+  /**
+   * Experimental. Set to NO_PROPAGATE to prevent error propagation. Set to ABORT to
+   * abort a request when any error occurs.
+   *
+   * Default: PROPAGATE
+   *
+   * @experimental
+   */
+  onError?: ErrorBehavior;
   /** Additional execution options. */
   options?: {
     /** Set the maximum number of errors allowed for coercing (defaults to 50). */
@@ -291,9 +303,18 @@ export function buildExecutionContext(
     fieldResolver,
     typeResolver,
     subscribeFieldResolver,
+    onError,
     options,
   } = args;
 
+  if (onError != null && !isErrorBehavior(onError)) {
+    return [
+      new GraphQLError(
+        'Unsupported `onError` value; supported values are `NO_PROPAGATE`, `PROPAGATE` and `ABORT`.',
+      ),
+    ];
+  }
+
   let operation: OperationDefinitionNode | undefined;
   const fragments: ObjMap<FragmentDefinitionNode> = Object.create(null);
   for (const definition of document.definitions) {
@@ -353,6 +374,7 @@ export function buildExecutionContext(
     typeResolver: typeResolver ?? defaultTypeResolver,
     subscribeFieldResolver: subscribeFieldResolver ?? defaultFieldResolver,
     errors: [],
+    errorBehavior: onError ?? schema.defaultErrorBehavior,
   };
 }
 
@@ -591,6 +613,7 @@ export function buildResolveInfo(
     rootValue: exeContext.rootValue,
     operation: exeContext.operation,
     variableValues: exeContext.variableValues,
+    errorBehavior: exeContext.errorBehavior,
   };
 }
 
@@ -599,10 +622,26 @@ function handleFieldError(
   returnType: GraphQLOutputType,
   exeContext: ExecutionContext,
 ): null {
-  // If the field type is non-nullable, then it is resolved without any
-  // protection from errors, however it still properly locates the error.
-  if (isNonNullType(returnType)) {
+  if (exeContext.errorBehavior === 'PROPAGATE') {
+    // If the field type is non-nullable, then it is resolved without any
+    // protection from errors, however it still properly locates the error.
+    // Note: semantic non-null types are treated as nullable for the purposes
+    // of error handling.
+    if (isNonNullType(returnType)) {
+      throw error;
+    }
+  } else if (exeContext.errorBehavior === 'ABORT') {
+    // In this mode, any error aborts the request
     throw error;
+  } else if (exeContext.errorBehavior === 'NO_PROPAGATE') {
+    // In this mode, the client takes responsibility for error handling, so we
+    // treat the field as if it were nullable.
+    /* c8 ignore next 6 */
+  } else {
+    invariant(
+      false,
+      'Unexpected errorBehavior setting: ' + inspect(exeContext.errorBehavior),
+    );
   }
 
   // Otherwise, error protection is applied, logging the error and resolving