Backport GraphQLError toJSON method to v15

src/error/GraphQLError.d.ts

@@ -4,6 +4,9 @@ import { ASTNode } from '../language/ast';
 import { Source } from '../language/source';
 import { SourceLocation } from '../language/location';
 
+// eslint-disable-next-line import/no-cycle
+import { GraphQLFormattedError } from './formatError';
+
 /**
  * Custom extensions
  *
@@ -82,6 +85,10 @@ export class GraphQLError extends Error {
    * Extension fields to add to the formatted error.
    */
   readonly extensions: { [key: string]: any };
+
+  toString(): string;
+
+  toJSON(): GraphQLFormattedError;
 }
 
 /**

src/error/GraphQLError.js

@@ -7,6 +7,9 @@ import type { SourceLocation } from '../language/location';
 import { getLocation } from '../language/location';
 import { printLocation, printSourceLocation } from '../language/printLocation';
 
+import { formatError } from './formatError';
+import type { GraphQLFormattedError } from './formatError';
+
 /**
  * A GraphQLError describes an Error found during the parse, validate, or
  * execute phases of performing a GraphQL operation. In addition to a message
@@ -157,6 +160,10 @@ export class GraphQLError extends Error {
     return printError(this);
   }
 
+  toJSON(): GraphQLFormattedError {
+    return formatError(this);
+  }
+
   // FIXME: workaround to not break chai comparisons, should be remove in v16
   // $FlowFixMe[unsupported-syntax] Flow doesn't support computed properties yet
   get [SYMBOL_TO_STRING_TAG](): string {

src/error/__tests__/GraphQLError-test.js

@@ -293,3 +293,52 @@ describe('printError', () => {
     `);
   });
 });
+
+describe('toJSON', () => {
+  it('includes path', () => {
+    const error = new GraphQLError('msg', null, null, null, [
+      'path',
+      3,
+      'to',
+      'field',
+    ]);
+
+    expect(error.toJSON()).to.deep.equal({
+      message: 'msg',
+      locations: undefined,
+      path: ['path', 3, 'to', 'field'],
+    });
+  });
+
+  it('includes extension fields', () => {
+    const error = new GraphQLError('msg', null, null, null, null, null, {
+      foo: 'bar',
+    });
+
+    expect(error.toJSON()).to.deep.equal({
+      message: 'msg',
+      locations: undefined,
+      path: undefined,
+      extensions: { foo: 'bar' },
+    });
+  });
+
+  it('can be created with full argument list', () => {
+    const error = new GraphQLError(
+      'msg',
+      [operationNode],
+      source,
+      [6],
+      ['path', 2, 'a'],
+      new Error('I like turtles'),
+      { hee: 'I like turtles' },
+    );
+
+    expect(error.toJSON()).to.deep.equal({
+      message: 'msg',
+      locations: [{ column: 5, line: 2 }],
+      path: ['path', 2, 'a'],
+      extensions: { hee: 'I like turtles' },
+    });
+  });
+});

src/error/formatError.d.ts

@@ -1,5 +1,6 @@
 import { SourceLocation } from '../language/location';
 
+// eslint-disable-next-line import/no-cycle
 import { GraphQLError } from './GraphQLError';
 
 /**