Allow mail to be sent to multiple recipients

Now the recipients argument must be a list, but everywhere
that we use this it already was.

Add some additional error checking to ensure that configuration is good
before sending the message

brainzutils/mail.py

@@ -2,12 +2,14 @@
 from email.mime.application import MIMEApplication
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
-from flask import current_app
-
+from typing import List
 import smtplib
 import socket
 
-def send_mail(subject, text, recipients, attachments=None,
+from flask import current_app
+
+
+def send_mail(subject: str, text: str, recipients: List[str], attachments=None,
               from_name="MetaBrainz Notifications",
               from_addr=None, boundary=None):
     """This function can be used as a foundation for sending email.
@@ -21,6 +23,12 @@ def send_mail(subject, text, recipients, attachments=None,
         from_name: Name of the sender.
         from_addr: Email address of the sender.
     """
+    if not isinstance(recipients, list):
+        raise ValueError("recipients must be a list of email addresses")
+
+    if 'SMTP_SERVER' not in current_app.config or 'SMTP_PORT' not in current_app.config:
+        raise ValueError("Flask current_app requires config items SMTP_SERVER and SMTP_PORT to be set")
+
     if attachments is None:
         attachments = []
     if from_addr is None:
@@ -32,12 +40,12 @@ def send_mail(subject, text, recipients, attachments=None,
     if not recipients:
         return
 
-    message =MIMEMultipart()
+    message = MIMEMultipart()
 
     if boundary is not None:
         message = MIMEMultipart(boundary=boundary)
 
-    message['To']="<%s>" %(recipients)
+    message['To'] = ", ".join(recipients)
     message['Subject'] = subject
     message['From'] = "%s <%s>" % (from_name, from_addr)
     message.attach(MIMEText(text, _charset='utf-8'))

brainzutils/test/test_mail.py

@@ -2,37 +2,66 @@
 import smtplib
 from unittest import mock
 
-from email.mime.application import MIMEApplication
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
 from brainzutils import flask
 from brainzutils import mail
 
 class MailTestCase(unittest.TestCase):
 
+    def test_send_email_missing_config(self):
+        app = flask.CustomFlask(__name__)
+        with app.app_context():
+            with self.assertRaises(ValueError) as err:
+                mail.send_mail(
+                    subject='ListenBrainz Spotify Importer Error',
+                    text='It is a test mail',
+                    recipients=[],
+                    attachments=None,
+                    from_name='ListenBrainz',
+                    from_addr='[email protected]',
+                    boundary='b'
+                )
+            assert "Flask current_app requires config items" in str(err.exception)
+
+    def test_send_email_string_recipients(self):
+        app = flask.CustomFlask(__name__)
+        with app.app_context():
+            with self.assertRaises(ValueError) as err:
+                mail.send_mail(
+                    subject='ListenBrainz Spotify Importer Error',
+                    text='It is a test mail',
+                    recipients='[email protected]',
+                    attachments=None,
+                    from_name='ListenBrainz',
+                    from_addr='[email protected]',
+                    boundary='b'
+                )
+            assert str(err.exception) == "recipients must be a list of email addresses"
+
     @mock.patch('smtplib.SMTP')
     def test_send_email(self, mock_smtp):
         app = flask.CustomFlask(__name__)
         app.config['SMTP_SERVER'] = 'localhost'
-        app.config['SMTP_PORT'] = 8080
+        app.config['SMTP_PORT'] = 25
 
         with app.app_context():
             from_address = '[email protected]'
-            recipients = '[email protected]'
+            recipients = ['[email protected]', '[email protected]']
             text = 'It is a test mail'
             from_name = 'ListenBrainz'
             subject = 'ListenBrainz Spotify Importer Error'
             boundary = '===============2220963697271485568=='
             message = MIMEMultipart(boundary=boundary)
-            message['To'] = '<%s>' % (recipients)
+            message['To'] = "[email protected], [email protected]"
             message['Subject'] = subject
             message['From'] = '%s <%s>' % (from_name, from_address)
             message.attach(MIMEText(text, _charset='utf-8'))
 
             mail.send_mail(
                 subject='ListenBrainz Spotify Importer Error',
                 text='It is a test mail',
-                recipients='[email protected]',
+                recipients=recipients,
                 attachments=None,
                 from_name='ListenBrainz',
                 from_addr='[email protected]',