feat(mock): enhance errors & support interfaces

Author: gregberge

src/mock.js

@@ -3,6 +3,7 @@ import {
   buildClientSchema,
   execute,
   GraphQLObjectType,
+  GraphQLInterfaceType,
   GraphQLSchema,
 } from 'graphql'
 import {
@@ -21,7 +22,8 @@ export function generateSchemaFromIntrospectionResult(introspectionResult) {
     if (
       typeName.startsWith('__') ||
       typeName === 'Query' ||
-      !(type instanceof GraphQLObjectType)
+      (!(type instanceof GraphQLObjectType) &&
+        !(type instanceof GraphQLInterfaceType))
     ) {
       return fields
     }
@@ -64,6 +66,14 @@ function executeFragment(schema, fragmentDocument) {
   `
 
   const res = execute(schema, query)
+
+  if (res.errors && res.errors.length) {
+    throw res.errors[0]
+  }
+
+  if (res.data[fieldName] === undefined) {
+    throw new Error(`fraql: type "${typeName}" not found`)
+  }
   return res.data[fieldName]
 }
 

src/mock.test.js

@@ -108,6 +108,53 @@ describe('mock', () => {
       const data2 = mocker.mockFragment(fragment)
       expect(data2.coverPicture.cloudinaryId).toBe('Hello World')
     })
+
+    it('should throw an error if a type is not found', () => {
+      const fragment = gql`
+        fragment _ on WTF {
+          id
+          name
+        }
+      `
+
+      expect.assertions(1)
+      try {
+        mocker.mockFragment(fragment)
+      } catch (error) {
+        expect(error.message).toBe('fraql: type "WTF" not found')
+      }
+    })
+
+    it('should throw an error if an interface has no __typename', () => {
+      const fragment = gql`
+        fragment _ on Place {
+          id
+          name
+        }
+      `
+
+      expect.assertions(1)
+      try {
+        mocker.mockFragment(fragment, { mocks: { Place: () => ({}) } })
+      } catch (error) {
+        expect(error.message).toBe('Please return a __typename in "Place"')
+      }
+    })
+
+    it('should support interface', () => {
+      const fragment = gql`
+        fragment _ on Place {
+          id
+          name
+        }
+      `
+
+      const data = mocker.mockFragment(fragment, {
+        mocks: { Place: () => ({ __typename: 'Hotel' }) },
+      })
+
+      expect(data.id).toBeDefined()
+    })
   })
 
   describe('#fromFragments', () => {