emails: Log emails that are queued or sent in dev environment.

Tweaked by tabbott to add some comments and clarify the code.

templates/zerver/email.html

@@ -0,0 +1,16 @@
+{% if failed %}
+    <p>{{template}} failed to render: {{ reason }}</p>
+{% else %}
+    <h4>From: {{ from_email }}</h4>
+    <h4>To:
+        {% for recipient in recipients %}
+        {{ recipient }}&nbsp;
+        {% endfor %}
+    </h4>
+    <h4>Subject: {{subject}}</h4>
+    {% autoescape off %}
+    {{ html_message }}
+    {% endautoescape %}
+    <pre>{{ body }}</pre>
+{% endif %}
+<hr/>

zerver/lib/send_email.py

@@ -21,6 +21,35 @@ class FromAddress(object):
     SUPPORT = parseaddr(settings.ZULIP_ADMINISTRATOR)[1]
     NOREPLY = parseaddr(settings.NOREPLY_EMAIL_ADDRESS)[1]
 
+def log_email(email, template_prefix):
+    # type: (EmailMultiAlternatives, str) -> None
+    """Used in development to record sent emails in a nice HTML log"""
+    html_message = 'Missing HTML message'
+    if len(email.alternatives) > 0:
+        html_message = email.alternatives[0][0]
+
+    context = {
+        'template': template_prefix + ".html",
+        'subject': email.subject,
+        'from_email': email.from_email,
+        'recipients': email.to,
+        'body': email.body,
+        'html_message': html_message
+    }
+
+    new_email = loader.render_to_string('zerver/email.html', context)
+
+    # Read in the pre-existing log, so that we can add the new entry
+    # at the top.
+    try:
+        with open(settings.EMAIL_CONTENT_LOG_PATH, "r") as f:
+            previous_emails = f.read()
+    except FileNotFoundError:
+        previous_emails = ""
+
+    with open(settings.EMAIL_CONTENT_LOG_PATH, "w+") as f:
+        f.write(new_email + previous_emails)
+
 def build_email(template_prefix, to_user_id=None, to_email=None, from_name=None,
                 from_address=None, reply_to_email=None, context=None):
     # type: (str, Optional[int], Optional[Text], Optional[Text], Optional[Text], Optional[Text], Optional[Dict[str, Any]]) -> EmailMultiAlternatives
@@ -80,6 +109,9 @@ def send_email(template_prefix, to_user_id=None, to_email=None, from_name=None,
     template = template_prefix.split("/")[-1]
     logger.info("Sending %s email to %s" % (template, mail.to))
 
+    if settings.DEVELOPMENT:
+        log_email(mail, template_prefix)
+
     if mail.send() == 0:
         logger.error("Error sending %s email to %s" % (template, mail.to))
         raise EmailNotDeliveredException
@@ -95,6 +127,14 @@ def send_future_email(template_prefix, to_user_id=None, to_email=None, from_name
     email_fields = {'template_prefix': template_prefix, 'to_user_id': to_user_id, 'to_email': to_email,
                     'from_name': from_name, 'from_address': from_address, 'context': context}
 
+    if settings.DEVELOPMENT:
+        mail = build_email(template_prefix, to_user_id=to_user_id, to_email=to_email, from_name=from_name,
+                           from_address=from_address, context=context)
+        # Technically, this will be called.  But we currently don't
+        # run the `manage.py deliver_email` backend job in the
+        # development environment.
+        log_email(mail, template_prefix)
+
     assert (to_user_id is None) ^ (to_email is None)
     if to_user_id is not None:
         to_field = {'user_id': to_user_id}  # type: Dict[str, Any]

zerver/tests/test_signup.py

@@ -313,7 +313,7 @@ class LoginTest(ZulipTestCase):
         with queries_captured() as queries:
             self.register(self.nonreg_email('test'), "test")
         # Ensure the number of queries we make is not O(streams)
-        self.assert_length(queries, 67)
+        self.assert_length(queries, 69)
         user_profile = self.nonreg_user('test')
         self.assertEqual(get_session_dict_user(self.client.session), user_profile.id)
         self.assertFalse(user_profile.enable_stream_desktop_notifications)

zproject/dev_settings.py

@@ -6,6 +6,7 @@ import os
 from typing import Set
 
 LOCAL_UPLOADS_DIR = 'var/uploads'
+EMAIL_LOG_DIR = "/var/log/zulip/email.log"
 # Default to subdomains disabled in development until we can update
 # the development documentation to make sense with subdomains.
 REALMS_HAVE_SUBDOMAINS = False

zproject/settings.py

@@ -1007,6 +1007,7 @@ ZULIP_PATHS = [
     ("EMAIL_LOG_PATH", "/var/log/zulip/send_email.log"),
     ("EMAIL_MIRROR_LOG_PATH", "/var/log/zulip/email_mirror.log"),
     ("EMAIL_DELIVERER_LOG_PATH", "/var/log/zulip/email-deliverer.log"),
+    ("EMAIL_CONTENT_LOG_PATH", "/var/log/zulip/email_content.log"),
     ("LDAP_SYNC_LOG_PATH", "/var/log/zulip/sync_ldap_user_data.log"),
     ("QUEUE_ERROR_DIR", "/var/log/zulip/queue_error"),
     ("STATS_DIR", "/home/zulip/stats"),