Improve error handling when sending emails (#595)

In one case, we were not catching a family of possible exceptions
(socket.error), and in the two other cases there was no error handling at
all. Sending emails can easily fail if no email server is configured, so
it is really necessary to handle these errors instead of crashing with a
HTTP 500 error.

Refactor email sending code and add proper error handling.

Show alert messages that tell the user if an email was sent or if there
was an error.

When sending a password reminder email or inviting people by email, we
don't proceed to the next step in case of error, because sending emails is
the whole point of these actions.

1 files changed, 47 insertions, 19 deletions

diff --git a/ihatemoney/web.py b/ihatemoney/web.py
index ae124ac..6575720 100644
--- a/ihatemoney/web.py
+++ b/ihatemoney/web.py
@@ -12,7 +12,6 @@ from datetime import datetime
 from functools import wraps
 import json
 import os
-from smtplib import SMTPRecipientsRefused
 
 from dateutil.parser import parse
 from dateutil.relativedelta import relativedelta
@@ -60,6 +59,7 @@ from ihatemoney.utils import (
     list_of_dicts2json,
     render_localized_template,
     same_bill,
+    send_email,
 )
 
 main = Blueprint("main", __name__)
@@ -308,11 +308,21 @@ def create_project():
             msg = Message(
                 message_title, body=message_body, recipients=[project.contact_email]
             )
-            try:
-                current_app.mail.send(msg)
-            except SMTPRecipientsRefused:
-                flash(_("Error while sending reminder email"), category="danger")
-
+            success = send_email(msg)
+            if success:
+                flash(
+                    _("A reminder email has just been sent to you"), category="success"
+                )
+            else:
+                # Display the error as a simple "info" alert, because it's
+                # not critical and doesn't prevent using the project.
+                flash(
+                    _(
+                        "We tried to send you an reminder email, but there was an error. "
+                        "You can still use the project normally."
+                    ),
+                    category="info",
+                )
             # redirect the user to the next step (invite)
             flash(_("The project identifier is %(project)s", project=project.id))
             return redirect(url_for(".list_bills", project_id=project.id))
@@ -328,17 +338,25 @@ def remind_password():
             # get the project
             project = Project.query.get(form.id.data)
             # send a link to reset the password
-            current_app.mail.send(
-                Message(
-                    "password recovery",
-                    body=render_localized_template(
-                        "password_reminder", project=project
+            remind_message = Message(
+                "password recovery",
+                body=render_localized_template("password_reminder", project=project),
+                recipients=[project.contact_email],
+            )
+            success = send_email(remind_message)
+            if success:
+                return redirect(url_for(".password_reminder_sent"))
+            else:
+                flash(
+                    _(
+                        "Sorry, there was an error while sending you an email "
+                        "with password reset instructions. "
+                        "Please check the email configuration of the server "
+                        "or contact the administrator."
                     ),
-                    recipients=[project.contact_email],
+                    category="danger",
                 )
-            )
-            return redirect(url_for(".password_reminder_sent"))
-
+                # Fall-through: we stay on the same page and display the form again
     return render_template("password_reminder.html", form=form)
 
 
@@ -585,10 +603,20 @@ def invite():
                 body=message_body,
                 recipients=[email.strip() for email in form.emails.data.split(",")],
             )
-            current_app.mail.send(msg)
-            flash(_("Your invitations have been sent"))
-            return redirect(url_for(".list_bills"))
-
+            success = send_email(msg)
+            if success:
+                flash(_("Your invitations have been sent"), category="success")
+                return redirect(url_for(".list_bills"))
+            else:
+                flash(
+                    _(
+                        "Sorry, there was an error while trying to send the invitation emails. "
+                        "Please check the email configuration of the server "
+                        "or contact the administrator."
+                    ),
+                    category="danger",
+                )
+                # Fall-through: we stay on the same page and display the form again
     return render_template("send_invites.html", form=form)