Bug 1520662 - Ensure undeterministic load order is not causing crashes

common/Reducers.jsm

@@ -59,7 +59,7 @@ const INITIAL_STATE = {
     spocs: {
       spocs_endpoint: "",
       lastUpdated: null,
-      data: [],
+      data: {}, // {spocs: []}
     },
   },
   Search: {

content-src/components/DiscoveryStreamBase/DiscoveryStreamBase.jsx

@@ -37,7 +37,7 @@ export class _DiscoveryStreamBase extends React.PureComponent {
           items={component.properties.items} />);
       case "Hero":
         const items = Math.min(MAX_ROWS_HERO,
-          component.properties.items || component.data ? component.data.recommendations.length : 0);
+          component.properties.items || (component.data ? component.data.recommendations.length : 0));
         const rows = component.data ? component.data.recommendations.slice(0, items) : [];
         return (
           <ImpressionStats rows={rows} dispatch={this.props.dispatch} source={component.type}>

content-src/components/DiscoveryStreamComponents/List/List.jsx

@@ -46,7 +46,7 @@ export function _List(props) {
 
   return (
     <div>
-      <h3 className="ds-list-title">{props.header.title}</h3>
+      <h3 className="ds-list-title">{props.header && props.header.title}</h3>
       <hr className="ds-list-border" />
       <ul className="ds-list">{recMarkup}</ul>
     </div>

content-src/lib/selectLayoutRender.js

@@ -4,7 +4,7 @@ function calculateSpocs(component, spocs) {
   let spocIndex = 0;
   return component.spocs.positions.map(position => {
     const rickRoll = Math.random();
-    if (rickRoll <= component.spocs.probability) {
+    if (spocs.data.spocs[spocIndex] && rickRoll <= component.spocs.probability) {
       return {
         ...position,
         result: spocs.data.spocs[spocIndex++],
@@ -37,7 +37,7 @@ export const selectLayoutRender = createSelector(
         }
 
         // Calculate if we should display a spoc or not.
-        if (component.spocs) {
+        if (component.spocs && spocs.data.spocs && spocs.data.spocs.length) {
           component.spocs = {
             ...component.spocs,
             positions: calculateSpocs(component, spocs),