test_emails: Use zerver.lib.send_email for rendering email.

Previously the rendering code in test_emails.py did not match the rendering
code in send_email.py. This commit removes the duplication to reduce the
chance they drift in the future.

This commit also changes test_emails.html to ensure that we always display
both the HTML and text versions of an email.

templates/zerver/test_emails.html

@@ -8,13 +8,10 @@
             <p>Email failed to render: {{ email.reason }}</p>
         {% else %}
             <h4>Subject: {{email.subject}}</h4>
-            {% if email.text %}
-                <pre>{{ email.body }}</pre>
-            {% else %}
             {% autoescape off %}
-                {{ email.body }}
+            {{ email.html_message }}
             {% endautoescape %}
-            {% endif %}
+            <pre>{{ email.body }}</pre>
         {% endif %}
     {% endfor %}
 </div>

zerver/lib/send_email.py

@@ -16,8 +16,9 @@ def display_email(user):
     # https://github.com/zulip/zulip/issues/4676 is resolved
     return user.email
 
-def send_email(template_prefix, to_email, from_email=None, reply_to_email=None, context={}):
-    # type: (str, Text, Optional[Text], Optional[Text], Dict[str, Any]) -> bool
+# Intended only for test code
+def build_email(template_prefix, to_email, from_email=None, reply_to_email=None, context={}):
+    # type: (str, Text, Optional[Text], Optional[Text], Dict[str, Any]) -> EmailMultiAlternatives
     subject = loader.render_to_string(template_prefix + '.subject',
                                       context=context, using='Jinja2_plaintext').strip()
     message = loader.render_to_string(template_prefix + '.txt',
@@ -36,6 +37,12 @@ def send_email(template_prefix, to_email, from_email=None, reply_to_email=None,
     mail = EmailMultiAlternatives(subject, message, from_email, [to_email], reply_to=reply_to)
     if html_message is not None:
         mail.attach_alternative(html_message, 'text/html')
+    return mail
+
+def send_email(template_prefix, to_email, from_email=None, reply_to_email=None, context={}):
+    # type: (str, Text, Optional[Text], Optional[Text], Dict[str, Any]) -> bool
+    mail = build_email(template_prefix, to_email, from_email=from_email,
+                       reply_to_email=reply_to_email, context=context)
     return mail.send() > 0
 
 def send_email_to_user(template_prefix, user, from_email=None, context={}):

zerver/views/test_emails.py

@@ -7,6 +7,7 @@ from django.http import HttpRequest, HttpResponse
 from django.shortcuts import render
 from django.template import loader, TemplateDoesNotExist
 
+from zerver.lib.send_email import build_email
 from zerver.models import get_realm
 
 import os
@@ -74,28 +75,13 @@ def email_page(request):
         if template not in templates and template not in ignore:
             templates.append(template)
             try:
-                data.append(render_email(template, test_context))
+                email = build_email('zerver/emails/' + template, 'recipient@acme.com', context=test_context)
+                email_data = {
+                    'template': template,
+                    'subject': email.subject,
+                    'body': email.body,
+                    'html_message': email.alternatives[0][0] if len(email.alternatives) > 0 else 'Missing HTML message'}
+                data.append(email_data)
             except Exception as e:  # nocoverage
                 data.append({'template': template, 'failed': True, 'reason': e})
     return render(request, 'zerver/test_emails.html', {'emails': data})
-
-def render_email(template_prefix, context):
-    # type: (str, Dict[str, Any]) -> Dict[str, Any]
-    email = {}  # type: Dict[str, Any]
-    email['template'] = template_prefix
-    email['subject'] = loader.render_to_string('zerver/emails/' + template_prefix + '.subject', context).strip()
-    message = loader.render_to_string('zerver/emails/' + template_prefix + '.txt', context)
-
-    try:
-        html_message = loader.render_to_string('/zerver/emails/' + template_prefix + '.html', context)
-    except TemplateDoesNotExist:
-        html_message = None
-
-    if html_message is not None:
-        email['body'] = html_message
-        email['text'] = False
-    else:
-        email['body'] = message
-        email['text'] = True
-
-    return email