Return & display error information when fetching email texts.

This covers the case where we partially fetch a set of messages in a
thread for whatever reason.

kanmail/client/components/emails/ThreadMessage.jsx

@@ -6,6 +6,7 @@ import { openLink } from 'window.js';
 
 import Avatar from 'components/Avatar.jsx';
 import ThreadMessageAttachment from 'components/emails/ThreadMessageAttachment.jsx';
+import threadStore from 'stores/thread.js';
 
 import { ensureInView } from 'util/element.js';
 import { cleanHtml } from 'util/html.js';
@@ -364,6 +365,15 @@ export default class ThreadMessage extends React.Component {
             uid,
         } = this.props.message;
 
+        if (body.error) {
+            return <div>
+                Error fetching message content: {body.error}.&nbsp;
+                <a onClick={() => threadStore.reloadThread()}>
+                    Click here to reload the thread
+                </a>.
+            </div>;
+        }
+
         let html = body.html || body.text;
         if (this.state.showPlainText) {
             html = body.text;

kanmail/client/stores/thread.js

@@ -206,6 +206,10 @@ class ThreadStore extends BaseStore {
         });
     }
 
+    reloadThread() {
+        this.loadThread(this.props.thread);
+    }
+
     close(triggerUpdate=true) {
         if (!this.isOpen) {
             return;

kanmail/server/mail/__init__.py

@@ -164,9 +164,14 @@ def get_folder_email_texts(account_key, folder_name, uids):
     uid_to_html_part_number = {}
 
     uid_to_headers = folder.get_email_headers(uids)
+    uid_to_error = {}
 
     for uid in uids:
-        headers = uid_to_headers[uid]
+        headers = uid_to_headers.get(uid)
+
+        if not headers:
+            uid_to_error[uid] = 'Missing headers'
+            continue
 
         uid_to_allow_images[uid] = all(
             is_email_allowed_images(email)
@@ -192,6 +197,8 @@ def get_folder_email_texts(account_key, folder_name, uids):
             if text:
                 uid_parts.append((uid, text))
                 uid_to_text_part_number[uid] = text
+        else:
+            uid_to_error[uid] = 'No text or HTML content'
 
     uid_part_data = _get_folder_email_parts(account_key, folder_name, uid_parts)
 
@@ -213,6 +220,12 @@ def get_folder_email_texts(account_key, folder_name, uids):
             'text': text_data,
             'html': html_data,
         }
+
+    for uid, error in uid_to_error.items():
+        uid_part_data_with_cids[uid] = {
+            'error': error,
+        }
+
     return uid_part_data_with_cids