Make 'toJSON' definition explicit

.eslintrc.yml

@@ -201,7 +201,7 @@ rules:
   no-implicit-coercion: error
   no-implicit-globals: off
   no-implied-eval: error
-  no-invalid-this: off
+  no-invalid-this: error
   no-iterator: error
   no-labels: error
   no-lone-blocks: error

src/jsutils/__tests__/inspect-test.js

@@ -186,6 +186,7 @@ describe('inspect', () => {
     expect(inspect([[new Foo()]])).to.equal('[[[Bar]]]');
 
     const objectWithoutClassName = new (function () {
+      // eslint-disable-next-line no-invalid-this
       this.foo = 1;
     })();
     expect(inspect([[objectWithoutClassName]])).to.equal('[[[Object]]]');

src/jsutils/defineToJSON.js → src/jsutils/defineInspect.js

@@ -1,16 +1,17 @@
 // @flow strict
 
+import invariant from './invariant';
 import nodejsCustomInspectSymbol from './nodejsCustomInspectSymbol';
 
 /**
- * The `defineToJSON()` function defines toJSON() and inspect() prototype
- * methods, if no function provided they become aliases for toString().
+ * The `defineInspect()` function defines `inspect()` prototype method as alias of `toJSON`
  */
-export default function defineToJSON(
+export default function defineInspect(
   classObject: Class<any> | ((...args: Array<any>) => mixed),
-  fn?: () => mixed = classObject.prototype.toString,
 ): void {
-  classObject.prototype.toJSON = fn;
+  const fn = classObject.prototype.toJSON;
+  invariant(typeof fn === 'function');
+
   classObject.prototype.inspect = fn;
 
   /* istanbul ignore else (See: https://github.com/graphql/graphql-js/issues/2317) */

src/language/ast.d.ts

@@ -32,6 +32,8 @@ export class Location {
   readonly source: Source;
 
   constructor(startToken: Token, endToken: Token, source: Source);
+
+  toJSON(): { start: number; end: number };
 }
 
 /**
@@ -86,6 +88,13 @@ export class Token {
     prev: Token | null,
     value?: string,
   );
+
+  toJSON(): {
+    kind: TokenKindEnum;
+    value: string | undefined;
+    line: number;
+    column: number;
+  };
 }
 
 /**

src/language/ast.js

@@ -1,6 +1,6 @@
 // @flow strict
 
-import defineToJSON from '../jsutils/defineToJSON';
+import defineInspect from '../jsutils/defineInspect';
 
 import { type Source } from './source';
 import { type TokenKindEnum } from './tokenKind';
@@ -42,12 +42,14 @@ export class Location {
     this.endToken = endToken;
     this.source = source;
   }
+
+  toJSON(): {| start: number, end: number |} {
+    return { start: this.start, end: this.end };
+  }
 }
 
-// Print a simplified form when appearing in JSON/util.inspect.
-defineToJSON(Location, function () {
-  return { start: this.start, end: this.end };
-});
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(Location);
 
 /**
  * Represents a range of characters represented by a lexical token
@@ -110,17 +112,24 @@ export class Token {
     this.prev = prev;
     this.next = null;
   }
+
+  toJSON(): {|
+    kind: TokenKindEnum,
+    value: string | void,
+    line: number,
+    column: number,
+  |} {
+    return {
+      kind: this.kind,
+      value: this.value,
+      line: this.line,
+      column: this.column,
+    };
+  }
 }
 
-// Print a simplified form when appearing in JSON/util.inspect.
-defineToJSON(Token, function () {
-  return {
-    kind: this.kind,
-    value: this.value,
-    line: this.line,
-    column: this.column,
-  };
-});
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(Token);
 
 /**
  * @internal

src/type/definition.js

@@ -17,7 +17,7 @@ import instanceOf from '../jsutils/instanceOf';
 import didYouMean from '../jsutils/didYouMean';
 import isObjectLike from '../jsutils/isObjectLike';
 import identityFunc from '../jsutils/identityFunc';
-import defineToJSON from '../jsutils/defineToJSON';
+import defineInspect from '../jsutils/defineInspect';
 import suggestionList from '../jsutils/suggestionList';
 import { type PromiseOrValue } from '../jsutils/PromiseOrValue';
 import {
@@ -373,13 +373,18 @@ export function GraphQLList(ofType) {
   return '[' + String(this.ofType) + ']';
 };
 
+(GraphQLList.prototype: any).toJSON = function toJSON() {
+  return this.toString();
+};
+
 Object.defineProperty(GraphQLList.prototype, SYMBOL_TO_STRING_TAG, {
   get() {
     return 'GraphQLList';
   },
 });
 
-defineToJSON(GraphQLList);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLList);
 
 /**
  * Non-Null Type Wrapper
@@ -424,13 +429,18 @@ export function GraphQLNonNull(ofType) {
   return String(this.ofType) + '!';
 };
 
+(GraphQLNonNull.prototype: any).toJSON = function toJSON() {
+  return this.toString();
+};
+
 Object.defineProperty(GraphQLNonNull.prototype, SYMBOL_TO_STRING_TAG, {
   get() {
     return 'GraphQLNonNull';
   },
 });
 
-defineToJSON(GraphQLNonNull);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLNonNull);
 
 /**
  * These types wrap and modify other types
@@ -637,13 +647,18 @@ export class GraphQLScalarType {
     return this.name;
   }
 
+  toJSON(): string {
+    return this.toString();
+  }
+
   // $FlowFixMe Flow doesn't support computed properties yet
   get [SYMBOL_TO_STRING_TAG]() {
     return 'GraphQLScalarType';
   }
 }
 
-defineToJSON(GraphQLScalarType);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLScalarType);
 
 export type GraphQLScalarSerializer<TExternal> = (
   outputValue: mixed,
@@ -776,13 +791,18 @@ export class GraphQLObjectType {
     return this.name;
   }
 
+  toJSON(): string {
+    return this.toString();
+  }
+
   // $FlowFixMe Flow doesn't support computed properties yet
   get [SYMBOL_TO_STRING_TAG]() {
     return 'GraphQLObjectType';
   }
 }
 
-defineToJSON(GraphQLObjectType);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLObjectType);
 
 function defineInterfaces(
   config: $ReadOnly<
@@ -1086,13 +1106,18 @@ export class GraphQLInterfaceType {
     return this.name;
   }
 
+  toJSON(): string {
+    return this.toString();
+  }
+
   // $FlowFixMe Flow doesn't support computed properties yet
   get [SYMBOL_TO_STRING_TAG]() {
     return 'GraphQLInterfaceType';
   }
 }
 
-defineToJSON(GraphQLInterfaceType);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLInterfaceType);
 
 export type GraphQLInterfaceTypeConfig<TSource, TContext> = {|
   name: string,
@@ -1188,13 +1213,18 @@ export class GraphQLUnionType {
     return this.name;
   }
 
+  toJSON(): string {
+    return this.toString();
+  }
+
   // $FlowFixMe Flow doesn't support computed properties yet
   get [SYMBOL_TO_STRING_TAG]() {
     return 'GraphQLUnionType';
   }
 }
 
-defineToJSON(GraphQLUnionType);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLUnionType);
 
 function defineTypes(
   config: $ReadOnly<GraphQLUnionTypeConfig<mixed, mixed>>,
@@ -1361,13 +1391,18 @@ export class GraphQLEnumType /* <T> */ {
     return this.name;
   }
 
+  toJSON(): string {
+    return this.toString();
+  }
+
   // $FlowFixMe Flow doesn't support computed properties yet
   get [SYMBOL_TO_STRING_TAG]() {
     return 'GraphQLEnumType';
   }
 }
 
-defineToJSON(GraphQLEnumType);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLEnumType);
 
 function didYouMeanEnumValue(
   enumType: GraphQLEnumType,
@@ -1513,13 +1548,18 @@ export class GraphQLInputObjectType {
     return this.name;
   }
 
+  toJSON(): string {
+    return this.toString();
+  }
+
   // $FlowFixMe Flow doesn't support computed properties yet
   get [SYMBOL_TO_STRING_TAG]() {
     return 'GraphQLInputObjectType';
   }
 }
 
-defineToJSON(GraphQLInputObjectType);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLInputObjectType);
 
 function defineInputFieldMap(
   config: $ReadOnly<GraphQLInputObjectTypeConfig>,

src/type/directives.js

@@ -7,8 +7,8 @@ import inspect from '../jsutils/inspect';
 import toObjMap from '../jsutils/toObjMap';
 import devAssert from '../jsutils/devAssert';
 import instanceOf from '../jsutils/instanceOf';
-import defineToJSON from '../jsutils/defineToJSON';
 import isObjectLike from '../jsutils/isObjectLike';
+import defineInspect from '../jsutils/defineInspect';
 import {
   type ReadOnlyObjMap,
   type ReadOnlyObjMapLike,
@@ -112,13 +112,18 @@ export class GraphQLDirective {
     return '@' + this.name;
   }
 
+  toJSON(): string {
+    return this.toString();
+  }
+
   // $FlowFixMe Flow doesn't support computed properties yet
   get [SYMBOL_TO_STRING_TAG]() {
     return 'GraphQLDirective';
   }
 }
 
-defineToJSON(GraphQLDirective);
+// Print a simplified form when appearing in `inspect` and `util.inspect`.
+defineInspect(GraphQLDirective);
 
 export type GraphQLDirectiveConfig = {|
   name: string,