emails: Inline CSS in emails in build_email.

Previously, we had an architecture where CSS inlining for emails was
done at provision time in inline_email_css.py. This was necessary
because the library we were using for this, Premailer, was extremely
slow, and doing the inlining for every outgoing email would have been
prohibitively expensive.

Now that we've migrated to a more modern library that inlines the
small amount of CSS we have into emails nearly instantly, we are able
to remove the complex architecture built to work around Premailer
being slow and just do the CSS inlining as the final step in sending
each individual email.

This has several significant benefits:

* Removes a fiddly provisioning step that made the edit/refresh cycle
  for modifying email templates confusing; there's no longer a CSS
  inlining step that, if you forget to do it, results in your testing a
  stale variant of the email templates.
* Fixes internationalization problems related to translators working
  with pre-CSS-inlined emails, and then Django trying to apply the
  translators to the post-CSS-inlined version.
* Makes the send_custom_email pipeline simpler and easier to improve.

Signed-off-by: Daniil Fadeev <fadeevd@zulip.com>

docs/subsystems/email.md

@@ -13,12 +13,12 @@ with only a few things you need to know to get started.
 
 - All email templates are in `templates/zerver/emails/`. Each email has three
   template files: `<template_prefix>.subject.txt`, `<template_prefix>.txt`, and
-  `<template_prefix>.source.html`. Email templates, along with all other templates
+  `<template_prefix>.html`. Email templates, along with all other templates
   in the `templates/` directory, are Jinja2 templates.
-- Most of the CSS and HTML layout for emails is in `email_base.html`. Note
+- Most of the CSS and HTML layout for emails is in `email_base_default.html`. Note
   that email has to ship with all of its CSS and HTML, so nothing in
   `static/` is useful for an email. If you're adding new CSS or HTML for an
-  email, there's a decent chance it should go in `email_base.html`.
+  email, there's a decent chance it should go in `email_base_default.html`.
 - All email is eventually sent by `zerver.lib.send_email.send_email`. There
   are several other functions in `zerver.lib.send_email`, but all of them
   eventually call the `send_email` function. The most interesting one is
@@ -104,11 +104,6 @@ email_password = gmail_password
 
 ### Notes
 
-- After changing any HTML email or `email_base.html`, you need to run
-  `scripts/setup/inline_email_css.py` for the changes to be reflected
-  in the development environment. The script generates files like
-  `templates/zerver/emails/compiled/<template_prefix>.html`.
-
 - Images won't be displayed in a real email client unless you change
   the `base_image_uri` used for emails to a public URL such as
   `https://chat.zulip.org/static/images/emails` (image links to
@@ -134,29 +129,18 @@ using a combination of the
 [css-inline](https://github.com/Stranger6667/css-inline) library and having
 two copies of each email (plain-text and HTML).
 
-So for each email, there are two source templates: the `.txt` version
+So, for each email, there are two source templates: the `.txt` version
-(for plain-text format) as well as a `.source.html` template. The
+(for plain-text format) as well as a `.html` template. The `.txt` version
-`.txt` version is used directly; while the `.source.html` template is
+is used directly, while `.html` is processed by `css-inline`, which injects
-processed by `scripts/setup/inline_email_css.py` (generating a `.html` template
+the CSS we use for styling our emails (`templates/zerver/emails/email.css`)
-under `templates/zerver/emails/compiled`); that tool (powered by
+into the templates just before sending an email.
-`css-inline`) injects the CSS we use for styling our emails
-(`templates/zerver/emails/email.css`) into the templates inline.
-
-What this means is that when you're editing emails, **you need to run
-`scripts/setup/inline_email_css.py`** after making changes to see the changes
-take effect. Our tooling automatically runs this as part of
-`tools/provision` and production deployments; but you should bump
-`PROVISION_VERSION` when making changes to emails that change test
-behavior, or other developers will get test failures until they
-provision.
 
 While this model is great for the markup side, it isn't ideal for
 [translations](../translating/translating.md). The Django
 translation system works with exact strings, and having different new
 markup can require translators to re-translate strings, which can
 result in problems like needing 2 copies of each string (one for
-plain-text, one for HTML) and/or needing to re-translate a bunch of
+plain-text, one for HTML). Re-translating these strings is
-strings after making a CSS tweak. Re-translating these strings is
 relatively easy in Transifex, but annoying.
 
 So when writing email templates, we try to translate individual
@@ -166,7 +150,7 @@ translators to not have to deal with multiple versions of each string
 in our emails.
 
 One can test whether you did the translating part right by running
-`scripts/setup/inline_email_css.py && manage.py makemessages` and then searching
+`manage.py makemessages` and then searching
 for the strings in `locale/en/LC_MESSAGES/django.po`; if there
 are multiple copies or they contain CSS colors, you did it wrong.
 
@@ -179,5 +163,5 @@ code path for the "you don't have an account email" might not be,
 since we might not know what language to use in the second case.
 
 Future work in this space could be to actually generate the plain-text
-versions of emails from the `.source.html` markup, so that we don't
+versions of emails from the `.html` markup, so that we don't
 need to maintain two copies of each email's text.

scripts/setup/inline_email_css.py

@@ -1,91 +0,0 @@
-#!/usr/bin/env python3
-import os
-from typing import Set
-
-import css_inline
-
-ZULIP_PATH = os.path.join(os.path.dirname(os.path.abspath(__file__)), "../../")
-EMAIL_TEMPLATES_PATH = os.path.join(ZULIP_PATH, "templates", "zerver", "emails")
-CSS_SOURCE_PATH = os.path.join(EMAIL_TEMPLATES_PATH, "email.css")
-
-
-def get_inliner_instance() -> css_inline.CSSInliner:
-    with open(CSS_SOURCE_PATH) as file:
-        content = file.read()
-    return css_inline.CSSInliner(extra_css=content)
-
-
-inliner = get_inliner_instance()
-
-
-def inline_template(template_source_name: str) -> None:
-    template_name = template_source_name.split(".source.html")[0]
-    template_path = os.path.join(EMAIL_TEMPLATES_PATH, template_source_name)
-    compiled_template_path = os.path.join(
-        os.path.dirname(template_path), "compiled", os.path.basename(template_name) + ".html"
-    )
-
-    os.makedirs(os.path.dirname(compiled_template_path), exist_ok=True)
-
-    with open(template_path) as template_source_file:
-        template_str = template_source_file.read()
-    output = inliner.inline(template_str)
-
-    output = escape_jinja2_characters(output)
-
-    # Inline method of css-inline will try to complete the DOM tree,
-    # adding html, head, and body tags if they aren't there.
-    # While this is correct for the email_base_default template,
-    # it is wrong for the other templates that extend this
-    # template, since we'll end up with 2 copies of those tags.
-    # Thus, we strip this stuff out if the template extends
-    # another template.
-    if template_name not in ["email_base_default", "email_base_marketing", "macros"]:
-        output = strip_unnecessary_tags(output)
-
-    if (
-        "zerver/emails/compiled/email_base_default.html" in output
-        or "zerver/emails/compiled/email_base_marketing.html" in output
-        or "zerver/emails/email_base_messages.html" in output
-    ):
-        assert output.count("<html>") == 0
-        assert output.count("<body>") == 0
-        assert output.count("</html>") == 0
-        assert output.count("</body>") == 0
-
-    with open(compiled_template_path, "w") as final_template_file:
-        final_template_file.write(output)
-
-
-def escape_jinja2_characters(text: str) -> str:
-    escaped_jinja2_characters = [("%7B%7B%20", "{{ "), ("%20%7D%7D", " }}"), ("&gt;", ">")]
-    for escaped, original in escaped_jinja2_characters:
-        text = text.replace(escaped, original)
-    return text
-
-
-def strip_unnecessary_tags(text: str) -> str:
-    end_block = "</body></html>"
-    start_block = "{% extends"
-    start = text.find(start_block)
-    end = text.rfind(end_block)
-    if start != -1 and end != -1:
-        text = text[start:end]
-        return text
-    else:
-        raise ValueError(f"Template does not have {start_block} or {end_block}")
-
-
-def get_all_templates_from_directory(directory: str) -> Set[str]:
-    result = set()
-    for f in os.listdir(directory):
-        if f.endswith(".source.html"):
-            result.add(f)
-    return result
-
-
-if __name__ == "__main__":
-    templates_to_inline = get_all_templates_from_directory(EMAIL_TEMPLATES_PATH)
-
-    for template_source_name in templates_to_inline:
-        inline_template(template_source_name)

templates/zerver/development/dev_tools.html

@@ -45,9 +45,6 @@
                 </tr>
                 <tr>
                     <td><a href="/emails">/emails</a></td>
-                    <td><code>./scripts/setup/inline_email_css.py</code><br />
-                        Run the command if you made changes to source.html email templates.
-                    </td>
                     <td>View outgoing and example emails.</td>
                 </tr>
                 <tr>

templates/zerver/digest_base.html

@@ -16,7 +16,7 @@
                 <h1> Zulip digest </h1>
             </div>
             <div class="digest-email-html">
-                {% include 'zerver/emails/compiled/digest.html' %}
+                {% include 'zerver/emails/digest.html' %}
                 <img id="digest-footer" src="{{ static('images/emails/footer.png') }}"/>
             </div>
             <br />

templates/zerver/emails/confirm_new_email.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/email_logo.png" alt=""/>

templates/zerver/emails/confirm_registration.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/registration_confirmation.png" alt=""/>

templates/zerver/emails/custom_email_base.pre.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_marketing.html" %}
+{% extends "zerver/emails/email_base_marketing.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/email_logo.png" alt=""/>

templates/zerver/emails/deactivate.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/email_logo.png" alt=""/>

templates/zerver/emails/email_base_default.html

@@ -1,4 +1,4 @@
-{% import 'zerver/emails/compiled/macros.html' as  macros %}
+{% import 'zerver/emails/macros.html' as  macros %}
 <!DOCTYPE html>
 <html lang="en">
     <head>

templates/zerver/emails/email_base_marketing.html

@@ -1,4 +1,4 @@
-{% import 'zerver/emails/compiled/macros.html' as  macros %}
+{% import 'zerver/emails/macros.html' as  macros %}
 <!DOCTYPE html>
 <html lang="en">
     <head>

templates/zerver/emails/find_team.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/email_logo.png" alt=""/>

templates/zerver/emails/followup_day1.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/email_logo.png" alt=""/>

templates/zerver/emails/followup_day2.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/day2_1.png" alt=""/>

templates/zerver/emails/invitation.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/registration_confirmation.png" alt=""/>

templates/zerver/emails/invitation_reminder.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/invitation_reminder.png" alt=""/>

templates/zerver/emails/notify_change_in_email.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/email_logo.png" alt=""/>

templates/zerver/emails/notify_new_login.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block preheader %}
     {% trans organization_url=realm_uri %}Organization: {{ organization_url }} Time: {{ login_time }} Email: {{ user_email }}{% endtrans %}

templates/zerver/emails/password_reset.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/email_logo.png" alt=""/>

templates/zerver/emails/realm_auto_downgraded.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/email_logo.png" alt=""/>

templates/zerver/emails/realm_reactivation.html

@@ -1,4 +1,4 @@
-{% extends "zerver/emails/compiled/email_base_default.html" %}
+{% extends "zerver/emails/email_base_default.html" %}
 
 {% block illustration %}
 <img src="{{ email_images_base_uri }}/registration_confirmation.png" alt=""/>

tools/build-release-tarball

@@ -109,7 +109,7 @@ echo "$version" >version
 
 cd "$OUTPUT_DIR"
 
-tar --append -f "$TARBALL" "$prefix/prod-static" "$prefix/build_id" "$prefix/version" "$prefix/zulip-git-version" "$prefix/locale" "$prefix/staticfiles.json" "$prefix/templates/zerver/emails/compiled" "$prefix/webpack-stats-production.json"
+tar --append -f "$TARBALL" "$prefix/prod-static" "$prefix/build_id" "$prefix/version" "$prefix/zulip-git-version" "$prefix/locale" "$prefix/staticfiles.json" "$prefix/webpack-stats-production.json"
 
 rm -rf "$prefix"
 

tools/check-templates

@@ -23,7 +23,7 @@ EXCLUDED_FILES = [
     ## Test data Files for testing modules in tests
     "tools/tests/test_template_data",
     # Our parser doesn't handle the way its conditionals are layered
-    "templates/zerver/emails/missed_message.source.html",
+    "templates/zerver/emails/missed_message.html",
     # Previously unchecked and our parser doesn't like its indentation
     "web/images/icons/template.hbs",
     # Template checker recommends very hard to read indentation.

tools/lib/provision_inner.py

@@ -72,15 +72,6 @@ def compilemessages_paths() -> List[str]:
     return paths
 
 
-def inline_email_css_paths() -> List[str]:
-    paths = [
-        "scripts/setup/inline_email_css.py",
-        "templates/zerver/emails/email.css",
-    ]
-    paths += glob.glob("templates/zerver/emails/*.source.html")
-    return paths
-
-
 def configure_rabbitmq_paths() -> List[str]:
     paths = [
         "scripts/setup/configure-rabbitmq",
@@ -180,16 +171,6 @@ def need_to_run_compilemessages() -> bool:
     )
 
 
-def need_to_run_inline_email_css() -> bool:
-    if not os.path.exists("templates/zerver/emails/compiled/"):
-        return True
-
-    return is_digest_obsolete(
-        "last_email_source_files_hash",
-        inline_email_css_paths(),
-    )
-
-
 def need_to_run_configure_rabbitmq(settings_list: List[str]) -> bool:
     obsolete = is_digest_obsolete(
         "last_configure_rabbitmq_hash",
@@ -246,15 +227,6 @@ def main(options: argparse.Namespace) -> int:
     else:
         print("No need to run `tools/setup/build_timezone_values`.")
 
-    if options.is_force or need_to_run_inline_email_css():
-        run(["scripts/setup/inline_email_css.py"])
-        write_new_digest(
-            "last_email_source_files_hash",
-            inline_email_css_paths(),
-        )
-    else:
-        print("No need to run `scripts/setup/inline_email_css.py`.")
-
     if not options.is_build_release_tarball_only:
         # The following block is skipped when we just need the development
         # environment to build a release tarball.

tools/update-prod-static

@@ -33,9 +33,6 @@ setup_node_modules(production=True)
 # Build emoji
 run(["./tools/setup/emoji/build_emoji"])
 
-# Inline CSS in emails
-run(["./scripts/setup/inline_email_css.py"])
-
 # Copy over static files from the zulip_bots package
 run(["./tools/setup/generate_zulip_bots_static_files.py"])
 

zerver/lib/send_email.py

@@ -11,6 +11,7 @@ from email.utils import formataddr, parseaddr
 from typing import Any, Dict, Iterable, List, Mapping, Optional, Sequence, Tuple, Union
 
 import backoff
+import css_inline
 import orjson
 from django.conf import settings
 from django.core.mail import EmailMultiAlternatives, get_connection
@@ -21,18 +22,19 @@ from django.core.management import CommandError
 from django.db import transaction
 from django.http import HttpRequest
 from django.template import loader
-from django.template.exceptions import TemplateDoesNotExist
 from django.utils.timezone import now as timezone_now
 from django.utils.translation import gettext as _
 from django.utils.translation import override as override_language
 
 from confirmation.models import generate_key, one_click_unsubscribe_link
-from scripts.setup.inline_email_css import inline_template
 from zerver.lib.logging_util import log_to_file
 from zerver.models import EMAIL_TYPES, Realm, ScheduledEmail, UserProfile, get_user_profile_by_id
 from zproject.email_backends import EmailLogBackEnd, get_forward_address
 
 MAX_CONNECTION_TRIES = 3
+ZULIP_PATH = os.path.join(os.path.dirname(os.path.abspath(__file__)), "../../")
+EMAIL_TEMPLATES_PATH = os.path.join(ZULIP_PATH, "templates", "zerver", "emails")
+CSS_SOURCE_PATH = os.path.join(EMAIL_TEMPLATES_PATH, "email.css")
 
 ## Logging setup ##
 
@@ -40,6 +42,12 @@ logger = logging.getLogger("zulip.send_email")
 log_to_file(logger, settings.EMAIL_LOG_PATH)
 
 
+def get_inliner_instance() -> css_inline.CSSInliner:
+    with open(CSS_SOURCE_PATH) as file:
+        content = file.read()
+    return css_inline.CSSInliner(extra_css=content)
+
+
 class FromAddress:
     SUPPORT = parseaddr(settings.ZULIP_ADMINISTRATOR)[1]
     NOREPLY = parseaddr(settings.NOREPLY_EMAIL_ADDRESS)[1]
@@ -124,6 +132,10 @@ def build_email(
         "physical_address": settings.PHYSICAL_ADDRESS,
     }
 
+    def get_inlined_template(template: str) -> str:
+        inliner = get_inliner_instance()
+        return inliner.inline(template)
+
     def render_templates() -> Tuple[str, str, str]:
         email_subject = (
             loader.render_to_string(
@@ -136,14 +148,8 @@ def build_email(
             template_prefix + ".txt", context=context, using="Jinja2_plaintext"
         )
 
-        try:
+        html_message = loader.render_to_string(template_prefix + ".html", context)
-            html_message = loader.render_to_string(template_prefix + ".html", context)
+        return (get_inlined_template(html_message), message, email_subject)
-        except TemplateDoesNotExist:
-            emails_dir = os.path.dirname(template_prefix)
-            template = os.path.basename(template_prefix)
-            compiled_template_prefix = os.path.join(emails_dir, "compiled", template)
-            html_message = loader.render_to_string(compiled_template_prefix + ".html", context)
-        return (html_message, message, email_subject)
 
     # The i18n story for emails is a bit complicated.  For emails
     # going to a single user, we want to use the language that user
@@ -518,13 +524,12 @@ def send_custom_email(
         parsed_email_template = Parser(policy=default).parsestr(text)
         email_template_hash = hashlib.sha256(text.encode()).hexdigest()[0:32]
 
-    email_filename = f"custom/custom_email_{email_template_hash}.source.html"
     email_id = f"zerver/emails/custom/custom_email_{email_template_hash}"
     markdown_email_base_template_path = "templates/zerver/emails/custom_email_base.pre.html"
-    html_source_template_path = f"templates/{email_id}.source.html"
+    html_template_path = f"templates/{email_id}.html"
     plain_text_template_path = f"templates/{email_id}.txt"
     subject_path = f"templates/{email_id}.subject.txt"
-    os.makedirs(os.path.dirname(html_source_template_path), exist_ok=True)
+    os.makedirs(os.path.dirname(html_template_path), exist_ok=True)
 
     # First, we render the Markdown input file just like our
     # user-facing docs with render_markdown_path.
@@ -536,18 +541,13 @@ def send_custom_email(
     rendered_input = render_markdown_path(plain_text_template_path.replace("templates/", ""))
 
     # And then extend it with our standard email headers.
-    with open(html_source_template_path, "w") as f:
+    with open(html_template_path, "w") as f:
         with open(markdown_email_base_template_path) as base_template:
-            # Note that we're doing a hacky non-Jinja2 substitution here;
+            f.write(base_template.read())
-            # we do this because the normal render_markdown_path ordering
-            # doesn't commute properly with inline_email_css.
-            f.write(base_template.read().replace("{{ rendered_input }}", rendered_input))
 
     with open(subject_path, "w") as f:
         f.write(get_header(options.get("subject"), parsed_email_template.get("subject"), "subject"))
 
-    inline_template(email_filename)
-
     # Finally, we send the actual emails.
     for user_profile in users:
         if options.get("admins_only") and not user_profile.is_realm_admin:
@@ -556,6 +556,7 @@ def send_custom_email(
             "realm_uri": user_profile.realm.uri,
             "realm_name": user_profile.realm.name,
             "unsubscribe_link": one_click_unsubscribe_link(user_profile, "marketing"),
+            "rendered_input": rendered_input,
         }
         with suppress(EmailNotDeliveredError):
             send_email(

zerver/management/commands/makemessages.py

@@ -150,7 +150,6 @@ class Command(makemessages.Command):
         try:
             ignore_patterns = options.get("ignore_patterns", [])
             ignore_patterns.append("docs/*")
-            ignore_patterns.append("templates/zerver/emails/compiled/*")
             ignore_patterns.append("templates/zerver/emails/custom/*")
             ignore_patterns.append("var/*")
             options["ignore_patterns"] = ignore_patterns

zerver/tests/test_email_notifications.py

@@ -101,7 +101,7 @@ class TestCustomEmails(ZulipTestCase):
     def test_send_custom_email_headers(self) -> None:
         hamlet = self.example_user("hamlet")
         markdown_template_path = (
-            "zerver/tests/fixtures/email/custom_emails/email_base_headers_test.source.html"
+            "zerver/tests/fixtures/email/custom_emails/email_base_headers_test.html"
         )
         send_custom_email(
             [hamlet],
@@ -120,7 +120,9 @@ class TestCustomEmails(ZulipTestCase):
         hamlet = self.example_user("hamlet")
         from_name = "from_name_test"
         email_subject = "subject_test"
-        markdown_template_path = "zerver/tests/fixtures/email/custom_emails/email_base_headers_no_headers_test.source.html"
+        markdown_template_path = (
+            "zerver/tests/fixtures/email/custom_emails/email_base_headers_no_headers_test.html"
+        )
 
         from zerver.lib.send_email import NoEmailArgumentError
 
@@ -151,7 +153,7 @@ class TestCustomEmails(ZulipTestCase):
         from_name = "from_name_test"
         email_subject = "subject_test"
         markdown_template_path = (
-            "zerver/tests/fixtures/email/custom_emails/email_base_headers_test.source.html"
+            "zerver/tests/fixtures/email/custom_emails/email_base_headers_test.html"
         )
 
         from zerver.lib.send_email import DoubledEmailArgumentError
@@ -185,7 +187,7 @@ class TestCustomEmails(ZulipTestCase):
         non_admin_user = self.example_user("cordelia")
 
         markdown_template_path = (
-            "zerver/tests/fixtures/email/custom_emails/email_base_headers_test.source.html"
+            "zerver/tests/fixtures/email/custom_emails/email_base_headers_test.html"
         )
         send_custom_email(
             [admin_user, non_admin_user],
@@ -449,6 +451,10 @@ class TestMissedMessages(ZulipTestCase):
         s = s.strip()
         return re.sub(r"\s+", " ", s)
 
+    def remove_style_attribute(self, s: str) -> str:
+        pattern = r'\sstyle="[^"]+"'
+        return re.sub(pattern, "", s)
+
     def _get_tokens(self) -> List[str]:
         return ["mm" + str(random.getrandbits(32)) for _ in range(30)]
 
@@ -463,6 +469,7 @@ class TestMissedMessages(ZulipTestCase):
         verify_body_does_not_include: Sequence[str] = [],
         trigger: str = "",
         mentioned_user_group_id: Optional[int] = None,
+        remove_style: bool = False,
     ) -> None:
         othello = self.example_user("othello")
         hamlet = self.example_user("hamlet")
@@ -500,7 +507,10 @@ class TestMissedMessages(ZulipTestCase):
         if verify_html_body:
             for text in verify_body_include:
                 assert isinstance(msg.alternatives[0][0], str)
-                self.assertIn(text, self.normalize_string(msg.alternatives[0][0]))
+                html = self.normalize_string(msg.alternatives[0][0])
+                if remove_style:
+                    html = self.remove_style_attribute(html)
+                self.assertIn(text, html)
         else:
             for text in verify_body_include:
                 self.assertIn(text, self.normalize_string(msg.body))
@@ -1261,11 +1271,16 @@ class TestMissedMessages(ZulipTestCase):
             f"http://zulip.testserver/user_avatars/{realm.id}/emoji/images/{realm_emoji_id}.png"
         )
         verify_body_include = [
-            f'<img alt=":green_tick:" src="{realm_emoji_url}" title="green tick" style="height: 20px;">'
+            f'<img alt=":green_tick:" src="{realm_emoji_url}" title="green tick">'
         ]
         email_subject = "DMs with Othello, the Moor of Venice"
         self._test_cases(
-            msg_id, verify_body_include, email_subject, send_as_user=False, verify_html_body=True
+            msg_id,
+            verify_body_include,
+            email_subject,
+            send_as_user=False,
+            verify_html_body=True,
+            remove_style=True,
         )
 
     def test_emojiset_in_missed_message(self) -> None:
@@ -1278,11 +1293,16 @@ class TestMissedMessages(ZulipTestCase):
             "Extremely personal message with a hamburger :hamburger:!",
         )
         verify_body_include = [
-            '<img alt=":hamburger:" src="http://testserver/static/generated/emoji/images-twitter-64/1f354.png" title="hamburger" style="height: 20px;">'
+            '<img alt=":hamburger:" src="http://testserver/static/generated/emoji/images-twitter-64/1f354.png" title="hamburger">'
         ]
         email_subject = "DMs with Othello, the Moor of Venice"
         self._test_cases(
-            msg_id, verify_body_include, email_subject, send_as_user=False, verify_html_body=True
+            msg_id,
+            verify_body_include,
+            email_subject,
+            send_as_user=False,
+            verify_html_body=True,
+            remove_style=True,
         )
 
     def test_stream_link_in_missed_message(self) -> None:
@@ -1298,7 +1318,12 @@ class TestMissedMessages(ZulipTestCase):
         ]
         email_subject = "DMs with Othello, the Moor of Venice"
         self._test_cases(
-            msg_id, verify_body_include, email_subject, send_as_user=False, verify_html_body=True
+            msg_id,
+            verify_body_include,
+            email_subject,
+            send_as_user=False,
+            verify_html_body=True,
+            remove_style=True,
         )
 
     def test_pm_link_in_missed_message_header(self) -> None:
@@ -1338,7 +1363,8 @@ class TestMissedMessages(ZulipTestCase):
         self.assertIn("Iago:\n> @**King Hamlet**\n\n--\nYou are", mail.outbox[0].body)
         # If message content starts with <p> tag the sender name is appended inside the <p> tag.
         self.assertIn(
-            '<p><b>Iago</b>: <span class="user-mention"', mail.outbox[0].alternatives[0][0]
+            '<p><b>Iago</b>: <span class="user-mention"',
+            self.remove_style_attribute(mail.outbox[0].alternatives[0][0]),
         )
 
         assert isinstance(mail.outbox[1], EmailMultiAlternatives)
@@ -1346,8 +1372,8 @@ class TestMissedMessages(ZulipTestCase):
         self.assertIn("Iago:\n> * 1\n>  *2\n\n--\nYou are receiving", mail.outbox[1].body)
         # If message content does not starts with <p> tag sender name is appended before the <p> tag
         self.assertIn(
-            "       <b>Iago</b>: <div><ul>\n<li>1<br/>\n *2</li>\n</ul></div>\n",
+            "       <b>Iago</b>: <div><ul>\n<li>1<br>\n *2</li>\n</ul></div>\n",
-            mail.outbox[1].alternatives[0][0],
+            self.remove_style_attribute(mail.outbox[1].alternatives[0][0]),
         )
 
         assert isinstance(mail.outbox[2], EmailMultiAlternatives)
@@ -1356,7 +1382,7 @@ class TestMissedMessages(ZulipTestCase):
         # Sender name is not appended to message for PM missed messages
         self.assertIn(
             ">\n                    \n                        <div><p>Hello</p></div>\n",
-            mail.outbox[2].alternatives[0][0],
+            self.remove_style_attribute(mail.outbox[2].alternatives[0][0]),
         )
 
     def test_multiple_missed_personal_messages(self) -> None:

zerver/views/development/email_log.py

@@ -1,5 +1,4 @@
 import os
-import subprocess
 import urllib
 from contextlib import suppress
 from typing import Optional
@@ -52,13 +51,6 @@ def clear_emails(request: HttpRequest) -> HttpResponse:
 
 @require_safe
 def generate_all_emails(request: HttpRequest) -> HttpResponse:
-    if not settings.TEST_SUITE:  # nocoverage
-        # It's really convenient to automatically inline the email CSS
-        # here, since that saves a step when testing out changes to
-        # the email CSS.  But we don't run this inside the test suite,
-        # because by role, the tests shouldn't be doing a provision-like thing.
-        subprocess.check_call(["./scripts/setup/inline_email_css.py"])
-
     # We import the Django test client inside the view function,
     # because it isn't needed in production elsewhere, and not
     # importing it saves ~50ms of unnecessary manage.py startup time.