Fix schema link to return errors for unknown queries

src/link/schema/__tests__/schemaLink.ts

@@ -25,8 +25,6 @@ type Query {
 const schema = makeExecutableSchema({ typeDefs });
 
 describe('SchemaLink', () => {
-  const mockError = { throws: new TypeError('mock me') };
-
   it('raises warning if called with concat', () => {
     const link = new SchemaLink({ schema });
     const _warn = console.warn;
@@ -56,7 +54,9 @@ describe('SchemaLink', () => {
     });
     observable.subscribe({
       next,
-      error: error => expect(false),
+      error: () => {
+        throw new Error('Received error')
+      },
       complete: () => {
         expect(next).toHaveBeenCalledTimes(1);
         done();
@@ -65,23 +65,26 @@ describe('SchemaLink', () => {
   });
 
   it('calls error when fetch fails', done => {
-    const badSchema = makeExecutableSchema({ typeDefs });
-
-    const link = new SchemaLink({ schema: badSchema });
+    const schema = makeExecutableSchema({
+      typeDefs,
+      resolvers: {
+        Query: {
+          sampleQuery() {
+            throw new Error('Unauthorized');
+          }
+        }
+      }
+    });
+    const link = new SchemaLink({ schema });
     const observable = execute(link, {
       query: sampleQuery,
     });
-    observable.subscribe(
-      result => expect(false),
-      error => {
-        expect(error).toEqual(mockError.throws);
-        done();
-      },
-      () => {
-        expect(false);
-        done();
-      },
-    );
+    observable.subscribe(result => {
+      expect(result.errors).toBeTruthy()
+      expect(result.errors!.length).toBe(1)
+      expect(result.errors![0].message).toMatch(/Unauthorized/)
+      done();
+    });
   });
 
   it('supports query which is executed synchronously', done => {
@@ -101,7 +104,9 @@ describe('SchemaLink', () => {
     });
     observable.subscribe(
       next,
-      error => expect(false),
+      () => {
+        throw new Error('Received error')
+      },
       () => {
         expect(next).toHaveBeenCalledTimes(1);
         done();
@@ -192,4 +197,22 @@ describe('SchemaLink', () => {
       },
     );
   });
+
+  it('reports errors for unknown queries', done => {
+    const schema = makeExecutableSchema({typeDefs})
+    const link = new SchemaLink({ schema });
+    const observable = execute(link, {
+      query: gql`
+        query {
+          unknown
+        }
+      `
+    });
+    observable.subscribe(result => {
+      expect(result.errors).toBeTruthy()
+      expect(result.errors!.length).toBe(1)
+      expect(result.errors![0].message).toMatch(/Cannot query field "unknown"/)
+      done();
+    });
+  });
 });

src/link/schema/index.ts

@@ -1,4 +1,5 @@
 import { execute } from 'graphql/execution/execute';
+import { validate } from 'graphql/validation/validate';
 import { GraphQLSchema } from 'graphql/type/schema';
 
 import { ApolloLink, Operation, FetchResult } from '../core';
@@ -48,14 +49,21 @@ export class SchemaLink extends ApolloLink {
             ? this.context(operation)
             : this.context
         )
-      ).then(context => execute(
-        this.schema,
-        operation.query,
-        this.rootValue,
-        context,
-        operation.variables,
-        operation.operationName,
-      )).then(data => {
+      ).then(context => {
+        const validationErrors = validate(this.schema, operation.query);
+        if (validationErrors.length > 0) {
+          return { errors: validationErrors };
+        }
+
+        return execute(
+          this.schema,
+          operation.query,
+          this.rootValue,
+          context,
+          operation.variables,
+          operation.operationName,
+        )
+      }).then(data => {
         if (!observer.closed) {
           observer.next(data);
           observer.complete();