Add support for @experimental_disableErrorPropagation (graphql#4348)

~This pull request adds support for `@onError(action: NULL)` to disable
error propagation for error aware clients:~

This pull request adds support for
`@experimental_disableErrorPropagation` to disable error propagation for
error aware clients:

```graphql
"""
Disables error propagation.
"""
directive @experimental_disableErrorPropagation on QUERY | MUTATION | SUBSCRIPTION
```

I'm not super used to write TypeScript, feel free to amend the PR as
needed but I figured it'd be good to have.

The logic is unconditional. The matching
[graphql-java](graphql-java/graphql-java#3772)
PR has a specific opt-in flag so that it's not enabled by accident in
the very unlikely event that a schema already contains a matching
directive. Let me know if this is an issue.

Many thanks @JoviDeCroock for pointing me in the right direction 🙏

See graphql/nullability-wg#85
See graphql/graphql-spec#1050

---------

Co-authored-by: Jovi De Croock <[email protected]>

Author: 2 people

src/execution/__tests__/errorPropagation-test.ts

@@ -0,0 +1,74 @@
+import { describe, it } from 'mocha';
+
+import { expectJSON } from '../../__testUtils__/expectJSON.js';
+
+import type { PromiseOrValue } from '../../jsutils/PromiseOrValue.js';
+
+import { parse } from '../../language/parser.js';
+
+import { buildSchema } from '../../utilities/buildASTSchema.js';
+
+import type { ExecutionResult } from '../execute.js';
+import { execute } from '../execute.js';
+
+const syncError = new Error('bar');
+
+const throwingData = {
+  foo() {
+    throw syncError;
+  },
+};
+
+const schema = buildSchema(`
+  type Query {
+    foo : Int!
+  }
+
+  directive @experimental_disableErrorPropagation on QUERY | MUTATION | SUBSCRIPTION
+`);
+
+function executeQuery(
+  query: string,
+  rootValue: unknown,
+): PromiseOrValue<ExecutionResult> {
+  return execute({ schema, document: parse(query), rootValue });
+}
+
+describe('Execute: handles errors', () => {
+  it('with `@experimental_disableErrorPropagation returns null', async () => {
+    const query = `
+      query getFoo @experimental_disableErrorPropagation {
+        foo
+      }
+    `;
+    const result = await executeQuery(query, throwingData);
+    expectJSON(result).toDeepEqual({
+      data: { foo: null },
+      errors: [
+        {
+          message: 'bar',
+          path: ['foo'],
+          locations: [{ line: 3, column: 9 }],
+        },
+      ],
+    });
+  });
+  it('without `experimental_disableErrorPropagation` propagates the error', async () => {
+    const query = `
+      query getFoo {
+        foo
+      }
+    `;
+    const result = await executeQuery(query, throwingData);
+    expectJSON(result).toDeepEqual({
+      data: null,
+      errors: [
+        {
+          message: 'bar',
+          path: ['foo'],
+          locations: [{ line: 3, column: 9 }],
+        },
+      ],
+    });
+  });
+});

src/execution/execute.ts

@@ -44,6 +44,7 @@ import {
   isNonNullType,
   isObjectType,
 } from '../type/definition.js';
+import { GraphQLDisableErrorPropagationDirective } from '../type/directives.js';
 import type { GraphQLSchema } from '../type/schema.js';
 import { assertValidSchema } from '../type/validate.js';
 
@@ -150,6 +151,7 @@ export interface ExecutionContext {
   errors: Array<GraphQLError>;
   abortSignalListener: AbortSignalListener | undefined;
   completed: boolean;
+  errorPropagation: boolean;
 }
 
 /**
@@ -224,6 +226,15 @@ export function execute(args: ExecutionArgs): PromiseOrValue<ExecutionResult> {
   return executeQueryOrMutationOrSubscriptionEvent(validatedExecutionArgs);
 }
 
+function errorPropagation(operation: OperationDefinitionNode): boolean {
+  const directiveNode = operation.directives?.find(
+    (directive) =>
+      directive.name.value === GraphQLDisableErrorPropagationDirective.name,
+  );
+
+  return directiveNode === undefined;
+}
+
 /**
  * Implements the "Executing operations" section of the spec.
  *
@@ -250,6 +261,7 @@ export function executeQueryOrMutationOrSubscriptionEvent(
       ? new AbortSignalListener(abortSignal)
       : undefined,
     completed: false,
+    errorPropagation: errorPropagation(validatedExecutionArgs.operation),
   };
   try {
     const {
@@ -736,7 +748,7 @@ function handleFieldError(
 
   // 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.errorPropagation && isNonNullType(returnType)) {
     throw error;
   }
 

src/type/directives.ts

@@ -226,6 +226,19 @@ export const GraphQLOneOfDirective: GraphQLDirective = new GraphQLDirective({
   args: {},
 });
 
+/**
+ * Disables error propagation (experimental).
+ */
+export const GraphQLDisableErrorPropagationDirective = new GraphQLDirective({
+  name: 'experimental_disableErrorPropagation',
+  description: 'Disables error propagation.',
+  locations: [
+    DirectiveLocation.QUERY,
+    DirectiveLocation.MUTATION,
+    DirectiveLocation.SUBSCRIPTION,
+  ],
+});
+
 /**
  * The full list of specified directives.
  */