Add error handling to builder preview and loading indicator

packages/builder/assets/error.svg

@@ -0,0 +1,34 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" enable-background="new 0 0 48 48" height="48px" viewBox="0 0 48 48" width="48px" xml:space="preserve">
+  <g>
+    <g>
+      <path d="M9,42H3c-0.552,0-1-0.449-1-1v-3.5C2,37.224,2.224,37,2.5,37S3,37.224,3,37.5V41h6    c0.276,0,0.5,0.224,0.5,0.5S9.276,42,9,42z"/>
+        <path d="M45,42h-6c-0.276,0-0.5-0.224-0.5-0.5S38.724,41,39,41h6V13H3v27c0,0.276-0.224,0.5-0.5,0.5S2,40.276,2,40    V12h44v29C46,41.551,45.552,42,45,42z"/>
+        <g>
+        <path d="M45.5,13h-43C2.224,13,2,12.776,2,12.5v-5C2,6.673,2.673,6,3.5,6h41C45.327,6,46,6.673,46,7.5v5     C46,12.776,45.776,13,45.5,13z M3,12h42V7.5C45,7.224,44.775,7,44.5,7h-41C3.225,7,3,7.224,3,7.5V12z"/>
+      </g>
+        <g>
+        <g>
+          <path d="M16.5,11c-0.827,0-1.5-0.673-1.5-1.5S15.673,8,16.5,8S18,8.673,18,9.5S17.327,11,16.5,11z M16.5,9      C16.225,9,16,9.224,16,9.5s0.225,0.5,0.5,0.5S17,9.776,17,9.5S16.775,9,16.5,9z"/>
+        </g>
+            <g>
+          <path d="M11.5,11c-0.827,0-1.5-0.673-1.5-1.5S10.673,8,11.5,8S13,8.673,13,9.5S12.327,11,11.5,11z M11.5,9      C11.225,9,11,9.224,11,9.5s0.225,0.5,0.5,0.5S12,9.776,12,9.5S11.775,9,11.5,9z"/>
+        </g>
+            <g>
+          <path d="M6.5,11C5.673,11,5,10.327,5,9.5S5.673,8,6.5,8S8,8.673,8,9.5S7.327,11,6.5,11z M6.5,9      C6.225,9,6,9.224,6,9.5S6.225,10,6.5,10S7,9.776,7,9.5S6.775,9,6.5,9z"/>
+        </g>
+      </g>
+    </g>
+      <g>
+      <g>
+        <path d="M35.696,44H12.304c-0.728,0-1.313-0.284-1.605-0.779c-0.289-0.489-0.259-1.126,0.084-1.749L22.58,19.996     c0.709-1.285,2.132-1.285,2.839,0l11.799,21.477v0c0.343,0.623,0.373,1.26,0.084,1.749C37.01,43.716,36.424,44,35.696,44z M24,20     c-0.176,0-0.379,0.179-0.544,0.478L11.659,41.954c-0.168,0.306-0.205,0.582-0.101,0.758C11.667,42.895,11.938,43,12.304,43     h23.393c0.365,0,0.637-0.105,0.745-0.288c0.104-0.177,0.067-0.453-0.101-0.758v0L24.543,20.478C24.379,20.179,24.176,20,24,20z"/>
+      </g>
+          <g>
+        <path d="M24,36L24,36c-0.225,0-0.421-0.15-0.481-0.366C23.456,35.412,22,30.169,22,28c0-1.103,0.897-2,2-2     s2,0.897,2,2c0,2.232-1.457,7.417-1.519,7.636C24.42,35.851,24.224,36,24,36z M24,27c-0.552,0-1,0.449-1,1     c0,1.266,0.569,3.793,1.002,5.531C24.435,31.806,25,29.301,25,28C25,27.449,24.552,27,24,27z"/>
+      </g>
+          <g>
+        <path d="M24,41c-1.103,0-2-0.897-2-2s0.897-2,2-2s2,0.897,2,2S25.103,41,24,41z M24,38c-0.552,0-1,0.449-1,1     s0.448,1,1,1s1-0.449,1-1S24.552,38,24,38z"/>
+      </g>
+    </g>
+  </g>
+</svg>

packages/builder/src/components/design/AppPreview/CurrentItemPreview.svelte

@@ -5,12 +5,16 @@
   import { Screen } from "builderStore/store/screenTemplates/utils/Screen"
   import { FrontendTypes } from "constants"
   import ConfirmDialog from "components/common/ConfirmDialog.svelte"
+  import { ProgressCircle, Layout, Heading, Body } from "@budibase/bbui"
+  import ErrorSVG from "assets/error.svg?raw"
 
   let iframe
   let layout
   let screen
   let confirmDeleteDialog
   let idToDelete
+  let loading = true
+  let error
 
   // Create screen slot placeholder for use when a page is selected rather
   // than a screen
@@ -68,11 +72,21 @@
   onMount(() => {
     // Initialise the app when mounted
     iframe.contentWindow.addEventListener(
-      "bb-ready",
+      "ready",
       () => refreshContent(strippedJson),
       { once: true }
     )
 
+    // Catch any app errors
+    iframe.contentWindow.addEventListener(
+      "error",
+      event => {
+        loading = false
+        error = event.detail || "An unknown error occurred"
+      },
+      { once: true }
+    )
+
     // Add listener for events sent by cliebt library in preview
     iframe.contentWindow.addEventListener("bb-event", event => {
       const { type, data } = event.detail
@@ -83,8 +97,10 @@
       } else if (type === "delete-component" && data.id) {
         idToDelete = data.id
         confirmDeleteDialog.show()
+      } else if (type === "preview-loaded") {
+        loading = false
       } else {
-        console.log(data)
+        console.warning(`Client sent unknown event type: ${type}`)
       }
     })
   })
@@ -99,11 +115,25 @@
 </script>
 
 <div class="component-container">
+  {#if loading}
+    <div class="center">
+      <ProgressCircle />
+    </div>
+  {:else if error}
+    <div class="center error">
+      <Layout justifyItems="center" gap="S">
+        {@html ErrorSVG}
+        <Heading size="L">App preview failed to load</Heading>
+        <Body size="S">{error}</Body>
+      </Layout>
+    </div>
+  {/if}
   <iframe
     style="height: 100%; width: 100%"
     title="componentPreview"
     bind:this={iframe}
     srcdoc={template}
+    class:hidden={loading || error}
   />
 </div>
 <ConfirmDialog
@@ -131,4 +161,32 @@
     width: 100%;
     background-color: transparent;
   }
+  .center {
+    position: absolute;
+    width: 100%;
+    height: 100%;
+    display: grid;
+    place-items: center;
+    z-index: 1;
+  }
+  .hidden {
+    opacity: 0;
+  }
+  .error :global(svg) {
+    fill: var(--spectrum-global-color-gray-500);
+    width: 80px;
+    height: 80px;
+  }
+  .error :global(h1),
+  .error :global(p) {
+    color: var(--spectrum-global-color-gray-800);
+  }
+  .error :global(p) {
+    font-style: italic;
+    margin-top: -0.5em;
+  }
+  .error :global(h1) {
+    font-weight: 400;
+    margin: 0;
+  }
 </style>

packages/builder/src/components/design/AppPreview/iframeTemplate.js

@@ -25,7 +25,9 @@ export default `
         flex-direction: column;
         justify-content: flex-start;
         align-items: stretch;
-        box-shadow: 0 0 8px 0 rgba(0, 0, 0, 0.1);
+      }
+      html.loaded {
+        box-shadow: 0 2px 8px -2px rgba(0, 0, 0, 0.1);
       }
       body {
         flex: 1 1 auto;
@@ -58,13 +60,20 @@ export default `
         window["##BUDIBASE_PREVIEW_TYPE##"] = previewType
 
         // Initialise app
-        if (window.loadBudibase) {
+        try {
-          loadBudibase()
+          if (window.loadBudibase) {
+            window.loadBudibase()
+            document.documentElement.classList.add("loaded")
+          } else {
+            throw "The client library couldn't be loaded"
+          }
+        } catch (error) {
+          window.dispatchEvent(new CustomEvent("error", { detail: error }))
         }
       }
 
       window.addEventListener("message", receiveMessage)
-      window.dispatchEvent(new Event("bb-ready"))
+      window.dispatchEvent(new Event("ready"))
     </script>
   </head>
   <body/>

packages/client/src/components/ClientApp.svelte

@@ -31,6 +31,9 @@
     await initialise()
     await authStore.actions.fetchUser()
     dataLoaded = true
+    if ($builderStore.inBuilder) {
+      builderStore.actions.notifyLoaded()
+    }
   })
 
   // Register this as a refreshable datasource so that user changes cause

packages/client/src/store/builder.js

@@ -1,7 +1,7 @@
 import { writable, derived } from "svelte/store"
 import Manifest from "@budibase/standard-components/manifest.json"
 
-const dispatchEvent = (type, data) => {
+const dispatchEvent = (type, data = {}) => {
   window.dispatchEvent(
     new CustomEvent("bb-event", {
       detail: { type, data },
@@ -64,6 +64,9 @@ const createBuilderStore = () => {
     deleteComponent: id => {
       dispatchEvent("delete-component", { id })
     },
+    notifyLoaded: () => {
+      dispatchEvent("preview-loaded")
+    },
   }
   return {
     ...writableStore,