FIX: catch all server-side error when uploading a file

UX: always show a message to the user whenever an error happens on the server when uploading a file

app/assets/javascripts/discourse/components/composer-editor.js.es6

@@ -493,7 +493,7 @@ export default Ember.Component.extend({
       this._xhr = null;
 
       if (!userCancelled) {
-        displayErrorForUpload(data.jqXHR.responseJSON);
+        displayErrorForUpload(data);
       }
     });
 

app/assets/javascripts/discourse/lib/utilities.js.es6

@@ -334,17 +334,17 @@ export function getUploadMarkdown(upload) {
 }
 
 export function displayErrorForUpload(data) {
-  // deal with meaningful errors first
   if (data.jqXHR) {
     switch (data.jqXHR.status) {
       // cancelled by the user
-      case 0: return;
+      case 0:
+        return;
 
       // entity too large, usually returned from the web server
       case 413:
-              var type = uploadTypeFromFileName(data.files[0].name);
-              var maxSizeKB = Discourse.SiteSettings['max_' + type + '_size_kb'];
-              bootbox.alert(I18n.t('post.errors.file_too_large', { max_size_kb: maxSizeKB }));
+        const type = uploadTypeFromFileName(data.files[0].name);
+        const max_size_kb = Discourse.SiteSettings[`max_${type}_size_kb`];
+        bootbox.alert(I18n.t('post.errors.file_too_large', { max_size_kb }));
         return;
 
       // the error message is provided by the server

app/assets/javascripts/discourse/mixins/upload.js.es6

@@ -56,7 +56,7 @@ export default Em.Mixin.create({
     });
 
     $upload.on("fileuploadfail", (e, data) => {
-      displayErrorForUpload(data.jqXHR.responseJSON);
+      displayErrorForUpload(data);
       reset();
     });
   }.on("didInsertElement"),

app/controllers/uploads_controller.rb

@@ -26,6 +26,7 @@ class UploadsController < ApplicationController
     # note, atm hijack is processed in its own context and has not access to controller
     # longer term we may change this
     hijack do
+      begin
         info = UploadsController.create_upload(
           current_user: me,
           file: file,
@@ -36,9 +37,13 @@ class UploadsController < ApplicationController
           is_api: is_api,
           retain_hours: retain_hours
         )
+      rescue => e
+        render json: failed_json.merge(message: e.message&.split("\n")&.first), status: 422
+      else
         render json: UploadsController.serialize_upload(info), status: Upload === info ? 200 : 422
       end
     end
+  end
 
   def lookup_urls
     params.permit(short_urls: [])

config/locales/server.en.yml

@@ -2873,6 +2873,7 @@ en:
     store_failure: "Failed to store upload #%{upload_id} for user #%{user_id}."
     file_missing: "Sorry, you must provide a file to upload."
     empty: "Sorry, but the file you provided is empty."
+    png_to_jpg_conversion_failure_message: "An error happened when converting from PNG to JPG."
     attachments:
       too_large: "Sorry, the file you are trying to upload is too big (maximum size is %{max_size_kb}KB)."
     images:

lib/upload_creator.rb

@@ -163,7 +163,7 @@ class UploadCreator
     command << '-debug' << 'all' if debug
     command << output_file.path
 
-    Discourse::Utils.execute_command(*command, failure_message: "failed to convert png to jpg")
+    Discourse::Utils.execute_command(*command, failure_message: I18n.t("upload.png_to_jpg_conversion_failure_message"))
   end
 
   def should_downsize?