🐛 ✨Fix eval setCurrentStory error + make logging better (#837)

* fix: load existing story instead of iframe.html

* fix: reject with reason instead of nothing (undefined)

* fix: reject with Error object instead of string

* test: update expectations for storyErrored event

* feat: throw error or constant string when err missing

src/snapshots.js

@@ -199,7 +199,9 @@ export async function* takeStorybookSnapshots(percy, callback, { baseUrl, flags
     while (snapshots.length) {
       try {
         // use a single page to capture story snapshots without reloading
-        yield* withPage(percy, previewUrl, async function*(page) {
+        // loading an existing story instead of just iframe.html as that triggers `storyMissing` event
+        // This in turn leads to promise rejection and failure
+        yield* withPage(percy, `${previewUrl}?id=${snapshots[0].id}&viewMode=story`, async function*(page) {
           // determines when to retry page crashes
           lastCount = snapshots.length;
 

src/utils.js

@@ -142,7 +142,7 @@ export async function* withPage(percy, url, callback, retry) {
     return yield* yieldTo(callback(page));
   } catch (error) {
     // if the page crashed and retry returns truthy, try again
-    if (error?.message?.includes('crashed') && retry?.()) {
+    if (error.message?.includes('crashed') && retry?.()) {
       return yield* withPage(...arguments);
     }
 
@@ -247,9 +247,9 @@ export function evalSetCurrentStory({ waitFor }, story) {
     // resolve when rendered, reject on any other renderer event
     return new Promise((resolve, reject) => {
       channel.on('storyRendered', resolve);
-      channel.on('storyMissing', reject);
-      channel.on('storyErrored', reject);
-      channel.on('storyThrewException', reject);
+      channel.on('storyMissing', (err) => reject(err || new Error('Story Missing')));
+      channel.on('storyErrored', (err) => reject(err || new Error('Story Errored')));
+      channel.on('storyThrewException', (err) => reject(err || new Error('Story Threw Exception')));
     });
   });
 }