From 1c75a89433c82bafd31552670f7a0d6c6cd69e09 Mon Sep 17 00:00:00 2001
From: Tom Coleman <tom@thesnail.org>
Date: Tue, 25 Jul 2017 16:12:45 +1000
Subject: [PATCH] Throw an exception if you try to access a non-existant
 channel

---
 app/react-native/src/preview/index.js | 10 +++++++++-
 lib/addons/src/index.js               | 10 +++++++---
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/app/react-native/src/preview/index.js b/app/react-native/src/preview/index.js
index c5d253887083..c1e9931a3786 100644
--- a/app/react-native/src/preview/index.js
+++ b/app/react-native/src/preview/index.js
@@ -52,7 +52,15 @@ export default class Preview {
   getStorybookUI(params = {}) {
     return () => {
       let webUrl = null;
-      let channel = addons.getChannel();
+      let channel = null;
+
+      try {
+        channel = addons.getChannel();
+      } catch (e) {
+        // getChannel throws if the channel is not defined,
+        // which is fine in this case (we will define it below)
+      }
+
       if (params.resetStorybook || !channel) {
         const host = params.host || 'localhost';
 
diff --git a/lib/addons/src/index.js b/lib/addons/src/index.js
index ee3ae408b66e..a669b37dd5e3 100644
--- a/lib/addons/src/index.js
+++ b/lib/addons/src/index.js
@@ -2,15 +2,19 @@ export class AddonStore {
   constructor() {
     this.loaders = {};
     this.panels = {};
-    // this.channel should get overwritten by setChannel if package versions are
-    // correct and AddonStore is a proper singleton. If not, this will be null
-    // (currently required by @storybook/react-native getStorybookUI)
     this.channel = null;
     this.preview = null;
     this.database = null;
   }
 
   getChannel() {
+    // this.channel should get overwritten by setChannel if package versions are
+    // correct and AddonStore is a proper singleton. If not, throw.
+    if (!this.channel) {
+      throw new Error(
+        'Accessing nonexistent addons channel, see https://storybook.js.org/basics/faq/#why-is-there-no-addons-channel'
+      );
+    }
     return this.channel;
   }