javascript: make Uploader always throw the same kind of errors

A DirectUpload may fail for several reasons, and return many types of
errors (string, xhr response, Error objects, etc).

For convenience, wrap all these errors in a FileUploadError object.

- It makes easier for clients of the Uploader class to handle errors;
- It allows to propagate the error code and failure responsability.

app/javascript/new_design/dossiers/auto-upload-controller.js

@@ -18,6 +18,8 @@ export default class AutoUploadController {
     );
   }
 
+  // Create, upload and attach the file.
+  // On failure, display an error message and throw a FileUploadError.
   async start() {
     try {
       this._begin();
@@ -55,36 +57,15 @@ export default class AutoUploadController {
     this.input.disabled = false;
   }
 
-  _isError422(error) {
-    // Ajax errors have an xhr attribute
-    if (error && error.xhr && error.xhr.status == 422) return true;
-    // Rails DirectUpload errors are returned as a String, e.g. 'Error creating Blob for "Demain.txt". Status: 422'
-    if (error && error.toString().includes('422')) return true;
-
-    return false;
-  }
-
   _messageFromError(error) {
-    let allowRetry = !this._isError422(error);
+    let message = error.message || error.toString();
+    let canRetry = error.status && error.status != 422;
+
 
-    if (
-      error.xhr &&
-      error.xhr.status == 422 &&
-      error.response &&
-      error.response.errors &&
-      error.response.errors[0]
-    ) {
     return {
-        title: error.response.errors[0],
+      title: 'Le fichier n’a pas pu être envoyé.',
-        description: '',
+      description: message,
-        retry: allowRetry
+      retry: canRetry
-      };
-    } else {
-      return {
-        title: 'Une erreur s’est produite pendant l’envoi du fichier.',
-        description: error.message || error.toString(),
-        retry: allowRetry
-      };
     }
   }
 

app/javascript/shared/activestorage/errors.js

@@ -1,22 +0,0 @@
-// Convert an error message returned by DirectUpload to a proper error object.
-//
-// This function has two goals:
-// 1. Remove the file name from the DirectUpload error message
-//   (because the filename confuses Sentry error grouping)
-// 2. Create each kind of error on a different line
-//   (so that Sentry knows they are different kind of errors, from
-//   the line they were created.)
-export default function errorFromDirectUploadMessage(message) {
-  let matches = message.match(/ Status: [0-9]{1,3}/);
-  let status = (matches && matches[0]) || '';
-
-  if (message.includes('Error creating')) {
-    return new Error('Error creating file.' + status);
-  } else if (message.includes('Error storing')) {
-    return new Error('Error storing file.' + status);
-  } else if (message.includes('Error reading')) {
-    return new Error('Error reading file.' + status);
-  } else {
-    return new Error(message);
-  }
-}

app/javascript/shared/activestorage/file-upload-error.js

@@ -0,0 +1,67 @@
+// Error while reading the file client-side
+export const ERROR_CODE_READ = 'file-upload-read-error';
+// Error while creating the empty blob on the server
+export const ERROR_CODE_CREATE = 'file-upload-create-error';
+// Error while uploading the blob content
+export const ERROR_CODE_STORE = 'file-upload-store-error';
+// Error while attaching the blob to the record
+export const ERROR_CODE_ATTACH = 'file-upload-attach-error';
+
+// Failure on the client side (syntax error, error reading file, etc.)
+export const FAILURE_CLIENT = 'file-upload-failure-client';
+// Failure on the server side (typically non-200 response)
+export const FAILURE_SERVER = 'file-upload-failure-server';
+// Failure during the transfert (request aborted, connection lost, etc)
+export const FAILURE_CONNECTIVITY = 'file-upload-failure-connectivity';
+
+/**
+  Represent an error during a file upload.
+  */
+export default class FileUploadError extends Error {
+  constructor(message, status, code) {
+    super(message);
+    this.name = 'FileUploadError';
+    this.status = status;
+    this.code = code;
+  }
+
+  /**
+    Return the component responsible of the error (client, server or connectivity).
+    See FAILURE_* constants for values.
+    */
+  get failureReason() {
+    let isNetworkError = this.code != ERROR_CODE_READ;
+
+    if (isNetworkError && this.status != 0) {
+      return FAILURE_SERVER;
+    } else if (isNetworkError && this.status == 0) {
+      return FAILURE_CONNECTIVITY;
+    } else {
+      return FAILURE_CLIENT;
+    }
+  }
+}
+
+// Convert an error message returned by DirectUpload to a proper error object.
+//
+// This function has two goals:
+// 1. Remove the file name from the DirectUpload error message
+//   (because the filename confuses Sentry error grouping)
+// 2. Create each kind of error on a different line
+//   (so that Sentry knows they are different kind of errors, from
+//   the line they were created.)
+export function errorFromDirectUploadMessage(message) {
+  let matches = message.match(/ Status: [0-9]{1,3}/);
+  let status = (matches && parseInt(matches[0], 10)) || undefined;
+
+  // prettier-ignore
+  if (message.includes('Error reading')) {
+    return new FileUploadError('Error reading file.', status, ERROR_CODE_READ);
+  } else if (message.includes('Error creating')) {
+    return new FileUploadError('Error creating file.', status, ERROR_CODE_CREATE);
+  } else if (message.includes('Error storing')) {
+    return new FileUploadError('Error storing file.', status, ERROR_CODE_STORE);
+  } else {
+    return new FileUploadError(message, status, undefined);
+  }
+}

app/javascript/shared/activestorage/ujs.js

@@ -1,5 +1,5 @@
 import ProgressBar from './progress-bar';
-import errorFromDirectUploadMessage from './errors';
+import { errorFromDirectUploadMessage } from './file-upload-error';
 import { fire } from '@utils';
 
 const INITIALIZE_EVENT = 'direct-upload:initialize';

app/javascript/shared/activestorage/uploader.js

@@ -1,7 +1,7 @@
 import { DirectUpload } from '@rails/activestorage';
 import { ajax } from '@utils';
 import ProgressBar from './progress-bar';
-import errorFromDirectUploadMessage from './errors';
+import FileUploadError, { errorFromDirectUploadMessage, ERROR_CODE_ATTACH } from './file-upload-error';
 
 /**
   Uploader class is a delegate for DirectUpload instance
@@ -17,6 +17,7 @@ export default class Uploader {
   /**
     Upload (and optionally attach) the file.
     Returns the blob signed id on success.
+    Throws a FileUploadError on failure.
     */
   async start() {
     this.progressBar.start();
@@ -40,6 +41,7 @@ export default class Uploader {
 
   /**
     Upload the file using the DirectUpload instance, and return the blob signed_id.
+    Throws a FileUploadError on failure.
     */
   async _upload() {
     return new Promise((resolve, reject) => {
@@ -56,6 +58,8 @@ export default class Uploader {
 
   /**
     Attach the file by sending a POST request to the autoAttachUrl.
+    Throws a FileUploadError on failure (containing the first validation
+    error message, if any).
     */
   async _attach(blobSignedId) {
     const attachmentRequest = {
@@ -64,7 +68,16 @@ export default class Uploader {
       data: `blob_signed_id=${blobSignedId}`
     };
 
+    try {
       await ajax(attachmentRequest);
+    } catch (e) {
+      let message = e.response && e.response.errors && e.response.errors[0];
+      throw new FileUploadError(
+        message || 'Error attaching file.',
+        e.xhr.status,
+        ERROR_CODE_ATTACH
+      );
+    }
   }
 
   uploadRequestDidProgress(event) {