Implement onError proposal

Author: benjie

src/error/ErrorBehavior.ts

@@ -0,0 +1,9 @@
+export type GraphQLErrorBehavior = 'PROPAGATE' | 'NO_PROPAGATE' | 'ABORT';
+
+export function isErrorBehavior(
+  onError: unknown,
+): onError is GraphQLErrorBehavior {
+  return (
+    onError === 'PROPAGATE' || onError === 'NO_PROPAGATE' || onError === 'ABORT'
+  );
+}

src/error/index.ts

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

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 { GraphQLErrorBehavior } 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: GraphQLErrorBehavior;
 }
 
 /**
@@ -130,6 +133,7 @@ export interface ExecutionResult<
 > {
   errors?: ReadonlyArray<GraphQLError>;
   data?: TData | null;
+  onError?: GraphQLErrorBehavior;
   extensions?: TExtensions;
 }
 
@@ -152,6 +156,15 @@ 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?: GraphQLErrorBehavior;
   /** Additional execution options. */
   options?: {
     /** Set the maximum number of errors allowed for coercing (defaults to 50). */
@@ -291,9 +304,18 @@ export function buildExecutionContext(
     fieldResolver,
     typeResolver,
     subscribeFieldResolver,
+    onError,
     options,
   } = args;
 
+  if (onError != null && !isErrorBehavior(onError)) {
+    return [
+      new GraphQLError(
+        'Unsupported `onError` value; supported values are `PROPAGATE`, `NO_PROPAGATE` and `ABORT`.',
+      ),
+    ];
+  }
+
   let operation: OperationDefinitionNode | undefined;
   const fragments: ObjMap<FragmentDefinitionNode> = Object.create(null);
   for (const definition of document.definitions) {
@@ -353,6 +375,7 @@ export function buildExecutionContext(
     typeResolver: typeResolver ?? defaultTypeResolver,
     subscribeFieldResolver: subscribeFieldResolver ?? defaultFieldResolver,
     errors: [],
+    errorBehavior: onError ?? 'PROPAGATE',
   };
 }
 
@@ -591,6 +614,7 @@ export function buildResolveInfo(
     rootValue: exeContext.rootValue,
     operation: exeContext.operation,
     variableValues: exeContext.variableValues,
+    errorBehavior: exeContext.errorBehavior,
   };
 }
 
@@ -599,10 +623,25 @@ 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.
+  } else {
+    invariant(
+      false,
+      'Unexpected errorBehavior setting: ' + inspect(exeContext.errorBehavior),
+    );
   }
 
   // Otherwise, error protection is applied, logging the error and resolving

src/graphql.ts

@@ -3,6 +3,8 @@ import { isPromise } from './jsutils/isPromise';
 import type { Maybe } from './jsutils/Maybe';
 import type { PromiseOrValue } from './jsutils/PromiseOrValue';
 
+import type { GraphQLErrorBehavior } from './error/ErrorBehavior';
+
 import { parse } from './language/parser';
 import type { Source } from './language/source';
 
@@ -66,6 +68,15 @@ export interface GraphQLArgs {
   operationName?: Maybe<string>;
   fieldResolver?: Maybe<GraphQLFieldResolver<any, any>>;
   typeResolver?: Maybe<GraphQLTypeResolver<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?: GraphQLErrorBehavior;
 }
 
 export function graphql(args: GraphQLArgs): Promise<ExecutionResult> {
@@ -106,6 +117,7 @@ function graphqlImpl(args: GraphQLArgs): PromiseOrValue<ExecutionResult> {
     operationName,
     fieldResolver,
     typeResolver,
+    onError,
   } = args;
 
   // Validate Schema
@@ -138,5 +150,6 @@ function graphqlImpl(args: GraphQLArgs): PromiseOrValue<ExecutionResult> {
     operationName,
     fieldResolver,
     typeResolver,
+    onError,
   });
 }

src/index.ts

@@ -395,6 +395,7 @@ export {
 } from './error/index';
 
 export type {
+  GraphQLErrorBehavior,
   GraphQLErrorOptions,
   GraphQLFormattedError,
   GraphQLErrorExtensions,

src/type/definition.ts

@@ -14,6 +14,7 @@ import type { PromiseOrValue } from '../jsutils/PromiseOrValue';
 import { suggestionList } from '../jsutils/suggestionList';
 import { toObjMap } from '../jsutils/toObjMap';
 
+import type { GraphQLErrorBehavior } from '../error/ErrorBehavior';
 import { GraphQLError } from '../error/GraphQLError';
 
 import type {
@@ -988,6 +989,8 @@ export interface GraphQLResolveInfo {
   readonly rootValue: unknown;
   readonly operation: OperationDefinitionNode;
   readonly variableValues: { [variable: string]: unknown };
+  /** @experimental */
+  readonly errorBehavior: GraphQLErrorBehavior;
 }
 
 /**