Add benjie's suggested changes

Author: magicmark

cspell.yml

@@ -48,6 +48,7 @@ ignoreRegExpList:
 
 words:
   - graphiql
+  - metafield
   - uncoerce
   - uncoerced
 

src/language/__tests__/parser-test.ts

@@ -790,6 +790,60 @@ describe('Parser', () => {
       });
     });
 
+    it('parses __Type', () => {
+      const result = parseSchemaCoordinate('__Type');
+      expectJSON(result).toDeepEqual({
+        kind: Kind.TYPE_COORDINATE,
+        loc: { start: 0, end: 6 },
+        name: {
+          kind: Kind.NAME,
+          loc: { start: 0, end: 6 },
+          value: '__Type',
+        },
+      });
+    });
+
+    it('parses Type.__metafield', () => {
+      const result = parseSchemaCoordinate('Type.__metafield');
+      expectJSON(result).toDeepEqual({
+        kind: Kind.MEMBER_COORDINATE,
+        loc: { start: 0, end: 16 },
+        name: {
+          kind: Kind.NAME,
+          loc: { start: 0, end: 4 },
+          value: 'Type',
+        },
+        memberName: {
+          kind: Kind.NAME,
+          loc: { start: 5, end: 16 },
+          value: '__metafield',
+        },
+      });
+    });
+
+    it('parses Type.__metafield(arg:)', () => {
+      const result = parseSchemaCoordinate('Type.__metafield(arg:)');
+      expectJSON(result).toDeepEqual({
+        kind: Kind.ARGUMENT_COORDINATE,
+        loc: { start: 0, end: 22 },
+        name: {
+          kind: Kind.NAME,
+          loc: { start: 0, end: 4 },
+          value: 'Type',
+        },
+        fieldName: {
+          kind: Kind.NAME,
+          loc: { start: 5, end: 16 },
+          value: '__metafield',
+        },
+        argumentName: {
+          kind: Kind.NAME,
+          loc: { start: 17, end: 20 },
+          value: 'arg',
+        },
+      });
+    });
+
     it('rejects @ Name . Name', () => {
       expect(() => parseSchemaCoordinate('@myDirective.field'))
         .to.throw()

src/language/__tests__/printer-test.ts

@@ -308,6 +308,13 @@ describe('Printer: Query document', () => {
     );
     expect(print(parseSchemaCoordinate('@name'))).to.equal('@name');
     expect(print(parseSchemaCoordinate('@name(arg:)'))).to.equal('@name(arg:)');
+    expect(print(parseSchemaCoordinate('__Type'))).to.equal('__Type');
+    expect(print(parseSchemaCoordinate('Type.__metafield'))).to.equal(
+      'Type.__metafield',
+    );
+    expect(print(parseSchemaCoordinate('Type.__metafield(arg:)'))).to.equal(
+      'Type.__metafield(arg:)',
+    );
   });
 
   it('throws syntax error for ignored tokens in schema coordinates', () => {

src/utilities/__tests__/resolveSchemaCoordinate-test.ts

@@ -1,4 +1,4 @@
-import { expect } from 'chai';
+import { assert, expect } from 'chai';
 import { describe, it } from 'mocha';
 
 import type {
@@ -12,32 +12,32 @@ import type { GraphQLDirective } from '../../type/directives.js';
 import { buildSchema } from '../buildASTSchema.js';
 import { resolveSchemaCoordinate } from '../resolveSchemaCoordinate.js';
 
-describe('resolveSchemaCoordinate', () => {
-  const schema = buildSchema(`
-    type Query {
-      searchBusiness(criteria: SearchCriteria!): [Business]
-    }
-
-    input SearchCriteria {
-      name: String
-      filter: SearchFilter
-    }
-
-    enum SearchFilter {
-      OPEN_NOW
-      DELIVERS_TAKEOUT
-      VEGETARIAN_MENU
-    }
-
-    type Business {
-      id: ID
-      name: String
-      email: String @private(scope: "loggedIn")
-    }
-
-    directive @private(scope: String!) on FIELD_DEFINITION
-  `);
+const schema = buildSchema(`
+  type Query {
+    searchBusiness(criteria: SearchCriteria!): [Business]
+  }
+
+  input SearchCriteria {
+    name: String
+    filter: SearchFilter
+  }
+
+  enum SearchFilter {
+    OPEN_NOW
+    DELIVERS_TAKEOUT
+    VEGETARIAN_MENU
+  }
+
+  type Business {
+    id: ID
+    name: String
+    email: String @private(scope: "loggedIn")
+  }
 
+  directive @private(scope: String!) on FIELD_DEFINITION
+`);
+
+describe('resolveSchemaCoordinate', () => {
   it('resolves a Named Type', () => {
     expect(resolveSchemaCoordinate(schema, 'Business')).to.deep.equal({
       kind: 'NamedType',
@@ -181,10 +181,20 @@ describe('resolveSchemaCoordinate', () => {
       'Expected "unknown" to be defined as a directive in the schema.',
     );
   });
+});
 
+/*
+ * NOTE: the following are not required for spec compliance; resolution
+ * of meta-fields is implementation-defined.
+ *
+ * These tests are here to ensure a change of behavior will only be made
+ * in a semver-major release of GraphQL.js.
+ */
+describe('resolveSchemaCoordinate (meta-fields and introspection types)', () => {
   it('resolves a meta-field', () => {
     const type = schema.getType('Business') as GraphQLObjectType;
     const field = schema.getField(type, '__typename');
+    assert.ok(field);
     expect(
       resolveSchemaCoordinate(schema, 'Business.__typename'),
     ).to.deep.equal({

src/utilities/resolveSchemaCoordinate.ts

@@ -14,10 +14,14 @@ import type { Source } from '../language/source.js';
 
 import type {
   GraphQLArgument,
+  GraphQLEnumType,
   GraphQLEnumValue,
   GraphQLField,
   GraphQLInputField,
+  GraphQLInputObjectType,
+  GraphQLInterfaceType,
   GraphQLNamedType,
+  GraphQLObjectType,
 } from '../type/definition.js';
 import {
   isEnumType,
@@ -38,25 +42,25 @@ export interface ResolvedNamedType {
 
 export interface ResolvedField {
   readonly kind: 'Field';
-  readonly type: GraphQLNamedType;
+  readonly type: GraphQLObjectType | GraphQLInterfaceType;
   readonly field: GraphQLField<unknown, unknown>;
 }
 
 export interface ResolvedInputField {
   readonly kind: 'InputField';
-  readonly type: GraphQLNamedType;
+  readonly type: GraphQLInputObjectType;
   readonly inputField: GraphQLInputField;
 }
 
 export interface ResolvedEnumValue {
   readonly kind: 'EnumValue';
-  readonly type: GraphQLNamedType;
+  readonly type: GraphQLEnumType;
   readonly enumValue: GraphQLEnumValue;
 }
 
 export interface ResolvedFieldArgument {
   readonly kind: 'FieldArgument';
-  readonly type: GraphQLNamedType;
+  readonly type: GraphQLObjectType | GraphQLInterfaceType;
   readonly field: GraphQLField<unknown, unknown>;
   readonly fieldArgument: GraphQLArgument;
 }
@@ -83,8 +87,10 @@ export type ResolvedSchemaElement =
 
 /**
  * A schema coordinate is resolved in the context of a GraphQL schema to
- * uniquely identifies a schema element. It returns undefined if the schema
- * coordinate does not resolve to a schema element.
+ * uniquely identify a schema element. It returns undefined if the schema
+ * coordinate does not resolve to a schema element, meta-field, or introspection
+ * schema element. It will throw if the containing schema element (if
+ * applicable) does not exist.
  *
  * https://spec.graphql.org/draft/#sec-Schema-Coordinates.Semantics
  */