uploads: fix errors not being shown for failed disk uploads.

Fix the error message not being shown if an upload from disk failed for
whatever reason, for example because it was a corrupt or unsupported file.

app/components/file_upload_component/file_upload_component.html.erb

@@ -33,9 +33,7 @@
         <div class="dz-upload h-1" data-dz-uploadprogress></div>
       </div>
 
-      <div class="dz-error-message">
+      <div class="dz-error-message" data-dz-errormessage></div>
-        <p data-dz-errormessage></p>
-      </div>
     </div>
   </template>
 </div>

app/components/file_upload_component/file_upload_component.js

@@ -64,7 +64,7 @@ export default class FileUploadComponent {
     dropzone.on("success", file => {
       this.$dropzone.addClass("success");
       let upload = JSON.parse(file.xhr.response)
-      location.href = `/uploads/${upload.id}`;
+      this.pollStatus(upload);
     });
 
     dropzone.on("error", (file, msg) => {
@@ -85,11 +85,14 @@ export default class FileUploadComponent {
     e.preventDefault();
   }
 
+  onSubmit(e) {
+    let upload = e.originalEvent.detail[0];
+    this.pollStatus(upload);
+  }
+
   // Called after the upload is submitted via AJAX. Polls the upload until it
   // is complete, then redirects to the upload page.
-  async onSubmit(e) {
+  async pollStatus(upload) {
-    let upload = e.originalEvent.detail[0];
-
     this.$component.find("progress").removeClass("hidden");
     this.$component.find("input").attr("disabled", "disabled");
 
@@ -101,6 +104,7 @@ export default class FileUploadComponent {
     if (upload.status === "completed") {
       location.href = `/uploads/${upload.id}`;
     } else {
+      this.$dropzone.removeClass("success");
       this.$component.find("progress").addClass("hidden");
       this.$component.find("input").removeAttr("disabled");