Unwrap non-null types (#20)

* Unwrap non-null types during selection type inference

We ran into the following error when we had a non-null `edges` field in
our schema (with a non-null type within the collection):

    Cannot read property 'cursor' of undefined

This patch adds a similar non-null `edges` field to the schema and adds
code to unwrap non-null types when inferring the type of a selection.

* Unwrap non-null returnType during mutations

Author: jgwhite

addon/fields/selections/index.js

@@ -1,10 +1,20 @@
 import createFieldInfo from '../info/create';
 import { getFieldNameAndAlias } from '../name';
 import { fragmentFieldsReducer, inlineFragmentFieldsReducer } from './fragments';
-import { partial } from '../../utils';
+import { partial, unwrapNonNull } from '../../utils';
 
-const getFieldType = (type, fieldName) =>
-  fieldName !== '__typename' && type._fields[fieldName].type;
+const getFieldType = (type, fieldName) => {
+  if (fieldName === '__typename') {
+    return null;
+  }
+
+  type = unwrapNonNull(type);
+
+  let field = type._fields[fieldName];
+  let fieldType = unwrapNonNull(field.type);
+
+  return fieldType;
+}
 
 export const selectedFieldsReducer =
   (getFieldNameAndAlias, getFieldType, createFieldInfo, getType, type, fragments, selections, selection) => {

addon/mocks/mutation.js

@@ -1,4 +1,4 @@
-import { contextSet, isFunction, reduceKeys } from '../utils';
+import { contextSet, isFunction, reduceKeys, unwrapNonNull } from '../utils';
 import { getRecords } from '../db';
 import { resolveVarName } from '../filter/vars';
 
@@ -11,6 +11,8 @@ const mapVars = composeMapVars(resolveVarName);
 
 export const composeMockMutation = (getRecords, mapVars) =>
   (db, options = {}, _, vars, __, { fieldName, returnType }) => {
+    returnType = unwrapNonNull(returnType);
+
     let { mutations = {}, varsMap = {} } = options;
     let mutation = mutations[fieldName];
     let records = getRecords(db, returnType.name);

addon/utils.js

@@ -1,3 +1,5 @@
+import { GraphQLNonNull } from 'graphql';
+
 const sortEdgesKeysBeforePageInfo = (list) => list.sort();
 
 export function contextPush(context, k, v) {
@@ -35,3 +37,5 @@ export const composeReduceKeys = (sortKeys) =>
     sortKeys(Object.keys(obj)).reduce(reducerFn, defaultValue);
 
 export const reduceKeys = composeReduceKeys(sortEdgesKeysBeforePageInfo);
+
+export const unwrapNonNull = (type) => type instanceof GraphQLNonNull ? type.ofType : type;

tests/dummy/app/gql/schema.graphql

@@ -19,7 +19,7 @@ type LineItem {
 }
 
 type LineItemConnection {
-  edges: [LineItemEdge]
+  edges: [LineItemEdge!]!
   pageInfo: PageInfo!
 }
 
@@ -29,7 +29,7 @@ type LineItemEdge {
 }
 
 type Mutation {
-  updatePerson(id: ID!, personAttributes: PersonAttributes!): Person
+  updatePerson(id: ID!, personAttributes: PersonAttributes!): Person!
 }
 
 interface Node {