Use the default templates when a custom template file cannot be found (#8037)

Fixes https://github.com/matrix-org/synapse/issues/6583

15 files changed, 310 insertions, 290 deletions

diff --git a/changelog.d/8037.feature b/changelog.d/8037.feature
new file mode 100644
index 0000000000..2e5127477d
--- /dev/null
+++ b/changelog.d/8037.feature
@@ -0,0 +1 @@
+Use the default template file when its equivalent is not found in a custom template directory.
\ No newline at end of file
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index 9235b89fb1..f168853f67 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -2002,9 +2002,7 @@ email:
   # Directory in which Synapse will try to find the template files below.
   # If not set, default templates from within the Synapse package will be used.
   #
-  # DO NOT UNCOMMENT THIS SETTING unless you want to customise the templates.
-  # If you *do* uncomment it, you will need to make sure that all the templates
-  # below are in the directory.
+  # Do not uncomment this setting unless you want to customise the templates.
   #
   # Synapse will look for the following templates in this directory:
   #
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index fd137853b1..1417487427 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -18,12 +18,16 @@
 import argparse
 import errno
 import os
+import time
+import urllib.parse
 from collections import OrderedDict
 from hashlib import sha256
 from textwrap import dedent
-from typing import Any, List, MutableMapping, Optional
+from typing import Any, Callable, List, MutableMapping, Optional
 
 import attr
+import jinja2
+import pkg_resources
 import yaml
 
 
@@ -100,6 +104,11 @@ class Config(object):
     def __init__(self, root_config=None):
         self.root = root_config
 
+        # Get the path to the default Synapse template directory
+        self.default_template_dir = pkg_resources.resource_filename(
+            "synapse", "res/templates"
+        )
+
     def __getattr__(self, item: str) -> Any:
         """
         Try and fetch a configuration option that does not exist on this class.
@@ -184,6 +193,95 @@ class Config(object):
         with open(file_path) as file_stream:
             return file_stream.read()
 
+    def read_templates(
+        self, filenames: List[str], custom_template_directory: Optional[str] = None,
+    ) -> List[jinja2.Template]:
+        """Load a list of template files from disk using the given variables.
+
+        This function will attempt to load the given templates from the default Synapse
+        template directory. If `custom_template_directory` is supplied, that directory
+        is tried first.
+
+        Files read are treated as Jinja templates. These templates are not rendered yet.
+
+        Args:
+            filenames: A list of template filenames to read.
+
+            custom_template_directory: A directory to try to look for the templates
+                before using the default Synapse template directory instead.
+
+        Raises:
+            ConfigError: if the file's path is incorrect or otherwise cannot be read.
+
+        Returns:
+            A list of jinja2 templates.
+        """
+        templates = []
+        search_directories = [self.default_template_dir]
+
+        # The loader will first look in the custom template directory (if specified) for the
+        # given filename. If it doesn't find it, it will use the default template dir instead
+        if custom_template_directory:
+            # Check that the given template directory exists
+            if not self.path_exists(custom_template_directory):
+                raise ConfigError(
+                    "Configured template directory does not exist: %s"
+                    % (custom_template_directory,)
+                )
+
+            # Search the custom template directory as well
+            search_directories.insert(0, custom_template_directory)
+
+        loader = jinja2.FileSystemLoader(search_directories)
+        env = jinja2.Environment(loader=loader, autoescape=True)
+
+        # Update the environment with our custom filters
+        env.filters.update(
+            {
+                "format_ts": _format_ts_filter,
+                "mxc_to_http": _create_mxc_to_http_filter(self.public_baseurl),
+            }
+        )
+
+        for filename in filenames:
+            # Load the template
+            template = env.get_template(filename)
+            templates.append(template)
+
+        return templates
+
+
+def _format_ts_filter(value: int, format: str):
+    return time.strftime(format, time.localtime(value / 1000))
+
+
+def _create_mxc_to_http_filter(public_baseurl: str) -> Callable:
+    """Create and return a jinja2 filter that converts MXC urls to HTTP
+
+    Args:
+        public_baseurl: The public, accessible base URL of the homeserver
+    """
+
+    def mxc_to_http_filter(value, width, height, resize_method="crop"):
+        if value[0:6] != "mxc://":
+            return ""
+
+        server_and_media_id = value[6:]
+        fragment = None
+        if "#" in server_and_media_id:
+            server_and_media_id, fragment = server_and_media_id.split("#", 1)
+            fragment = "#" + fragment
+
+        params = {"width": width, "height": height, "method": resize_method}
+        return "%s_matrix/media/v1/thumbnail/%s?%s%s" % (
+            public_baseurl,
+            server_and_media_id,
+            urllib.parse.urlencode(params),
+            fragment or "",
+        )
+
+    return mxc_to_http_filter
+
 
 class RootConfig(object):
     """
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index a63acbdc63..7a796996c0 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -23,7 +23,6 @@ from enum import Enum
 from typing import Optional
 
 import attr
-import pkg_resources
 
 from ._base import Config, ConfigError
 
@@ -98,21 +97,18 @@ class EmailConfig(Config):
             if parsed[1] == "":
                 raise RuntimeError("Invalid notif_from address")
 
+        # A user-configurable template directory
         template_dir = email_config.get("template_dir")
-        # we need an absolute path, because we change directory after starting (and
-        # we don't yet know what auxiliary templates like mail.css we will need).
-        # (Note that loading as package_resources with jinja.PackageLoader doesn't
-        # work for the same reason.)
-        if not template_dir:
-            template_dir = pkg_resources.resource_filename("synapse", "res/templates")
-
-        self.email_template_dir = os.path.abspath(template_dir)
+        if isinstance(template_dir, str):
+            # We need an absolute path, because we change directory after starting (and
+            # we don't yet know what auxiliary templates like mail.css we will need).
+            template_dir = os.path.abspath(template_dir)
+        elif template_dir is not None:
+            # If template_dir is something other than a str or None, warn the user
+            raise ConfigError("Config option email.template_dir must be type str")
 
         self.email_enable_notifs = email_config.get("enable_notifs", False)
 
-        account_validity_config = config.get("account_validity") or {}
-        account_validity_renewal_enabled = account_validity_config.get("renew_at")
-
         self.threepid_behaviour_email = (
             # Have Synapse handle the email sending if account_threepid_delegates.email
             # is not defined
@@ -166,19 +162,6 @@ class EmailConfig(Config):
             email_config.get("validation_token_lifetime", "1h")
         )
 
-        if (
-            self.email_enable_notifs
-            or account_validity_renewal_enabled
-            or self.threepid_behaviour_email == ThreepidBehaviour.LOCAL
-        ):
-            # make sure we can import the required deps
-            import bleach
-            import jinja2
-
-            # prevent unused warnings
-            jinja2
-            bleach
-
         if self.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
             missing = []
             if not self.email_notif_from:
@@ -196,49 +179,49 @@ class EmailConfig(Config):
 
             # These email templates have placeholders in them, and thus must be
             # parsed using a templating engine during a request
-            self.email_password_reset_template_html = email_config.get(
+            password_reset_template_html = email_config.get(
                 "password_reset_template_html", "password_reset.html"
             )
-            self.email_password_reset_template_text = email_config.get(
+            password_reset_template_text = email_config.get(
                 "password_reset_template_text", "password_reset.txt"
             )
-            self.email_registration_template_html = email_config.get(
+            registration_template_html = email_config.get(
                 "registration_template_html", "registration.html"
             )
-            self.email_registration_template_text = email_config.get(
+            registration_template_text = email_config.get(
                 "registration_template_text", "registration.txt"
             )
-            self.email_add_threepid_template_html = email_config.get(
+            add_threepid_template_html = email_config.get(
                 "add_threepid_template_html", "add_threepid.html"
             )
-            self.email_add_threepid_template_text = email_config.get(
+            add_threepid_template_text = email_config.get(
                 "add_threepid_template_text", "add_threepid.txt"
             )
 
-            self.email_password_reset_template_failure_html = email_config.get(
+            password_reset_template_failure_html = email_config.get(
                 "password_reset_template_failure_html", "password_reset_failure.html"
             )
-            self.email_registration_template_failure_html = email_config.get(
+            registration_template_failure_html = email_config.get(
                 "registration_template_failure_html", "registration_failure.html"
             )
-            self.email_add_threepid_template_failure_html = email_config.get(
+            add_threepid_template_failure_html = email_config.get(
                 "add_threepid_template_failure_html", "add_threepid_failure.html"
             )
 
             # These templates do not support any placeholder variables, so we
             # will read them from disk once during setup
-            email_password_reset_template_success_html = email_config.get(
+            password_reset_template_success_html = email_config.get(
                 "password_reset_template_success_html", "password_reset_success.html"
             )
-            email_registration_template_success_html = email_config.get(
+            registration_template_success_html = email_config.get(
                 "registration_template_success_html", "registration_success.html"
             )
-            email_add_threepid_template_success_html = email_config.get(
+            add_threepid_template_success_html = email_config.get(
                 "add_threepid_template_success_html", "add_threepid_success.html"
             )
 
-            # Check templates exist
-            for f in [
+            # Read all templates from disk
+            (
                 self.email_password_reset_template_html,
                 self.email_password_reset_template_text,
                 self.email_registration_template_html,
@@ -248,32 +231,36 @@ class EmailConfig(Config):
                 self.email_password_reset_template_failure_html,
                 self.email_registration_template_failure_html,
                 self.email_add_threepid_template_failure_html,
-                email_password_reset_template_success_html,
-                email_registration_template_success_html,
-                email_add_threepid_template_success_html,
-            ]:
-                p = os.path.join(self.email_template_dir, f)
-                if not os.path.isfile(p):
-                    raise ConfigError("Unable to find template file %s" % (p,))
-
-            # Retrieve content of web templates
-            filepath = os.path.join(
-                self.email_template_dir, email_password_reset_template_success_html
+                password_reset_template_success_html_template,
+                registration_template_success_html_template,
+                add_threepid_template_success_html_template,
+            ) = self.read_templates(
+                [
+                    password_reset_template_html,
+                    password_reset_template_text,
+                    registration_template_html,
+                    registration_template_text,
+                    add_threepid_template_html,
+                    add_threepid_template_text,
+                    password_reset_template_failure_html,
+                    registration_template_failure_html,
+                    add_threepid_template_failure_html,
+                    password_reset_template_success_html,
+                    registration_template_success_html,
+                    add_threepid_template_success_html,
+                ],
+                template_dir,
             )
-            self.email_password_reset_template_success_html = self.read_file(
-                filepath, "email.password_reset_template_success_html"
-            )
-            filepath = os.path.join(
-                self.email_template_dir, email_registration_template_success_html
-            )
-            self.email_registration_template_success_html_content = self.read_file(
-                filepath, "email.registration_template_success_html"
+
+            # Render templates that do not contain any placeholders
+            self.email_password_reset_template_success_html_content = (
+                password_reset_template_success_html_template.render()
             )
-            filepath = os.path.join(
-                self.email_template_dir, email_add_threepid_template_success_html
+            self.email_registration_template_success_html_content = (
+                registration_template_success_html_template.render()
             )
-            self.email_add_threepid_template_success_html_content = self.read_file(
-                filepath, "email.add_threepid_template_success_html"
+            self.email_add_threepid_template_success_html_content = (
+                add_threepid_template_success_html_template.render()
             )
 
         if self.email_enable_notifs:
@@ -290,17 +277,19 @@ class EmailConfig(Config):
                     % (", ".join(missing),)
                 )
 
-            self.email_notif_template_html = email_config.get(
+            notif_template_html = email_config.get(
                 "notif_template_html", "notif_mail.html"
             )
-            self.email_notif_template_text = email_config.get(
+            notif_template_text = email_config.get(
                 "notif_template_text", "notif_mail.txt"
             )
 
-            for f in self.email_notif_template_text, self.email_notif_template_html:
-                p = os.path.join(self.email_template_dir, f)
-                if not os.path.isfile(p):
-                    raise ConfigError("Unable to find email template file %s" % (p,))
+            (
+                self.email_notif_template_html,
+                self.email_notif_template_text,
+            ) = self.read_templates(
+                [notif_template_html, notif_template_text], template_dir,
+            )
 
             self.email_notif_for_new_users = email_config.get(
                 "notif_for_new_users", True
@@ -309,18 +298,20 @@ class EmailConfig(Config):
                 "client_base_url", email_config.get("riot_base_url", None)
             )
 
-        if account_validity_renewal_enabled:
-            self.email_expiry_template_html = email_config.get(
+        if self.account_validity.renew_by_email_enabled:
+            expiry_template_html = email_config.get(
                 "expiry_template_html", "notice_expiry.html"
             )
-            self.email_expiry_template_text = email_config.get(
+            expiry_template_text = email_config.get(
                 "expiry_template_text", "notice_expiry.txt"
             )
 
-            for f in self.email_expiry_template_text, self.email_expiry_template_html:
-                p = os.path.join(self.email_template_dir, f)
-                if not os.path.isfile(p):
-                    raise ConfigError("Unable to find email template file %s" % (p,))
+            (
+                self.account_validity_template_html,
+                self.account_validity_template_text,
+            ) = self.read_templates(
+                [expiry_template_html, expiry_template_text], template_dir,
+            )
 
         subjects_config = email_config.get("subjects", {})
         subjects = {}
@@ -400,9 +391,7 @@ class EmailConfig(Config):
           # Directory in which Synapse will try to find the template files below.
           # If not set, default templates from within the Synapse package will be used.
           #
-          # DO NOT UNCOMMENT THIS SETTING unless you want to customise the templates.
-          # If you *do* uncomment it, you will need to make sure that all the templates
-          # below are in the directory.
+          # Do not uncomment this setting unless you want to customise the templates.
           #
           # Synapse will look for the following templates in this directory:
           #
diff --git a/synapse/config/saml2_config.py b/synapse/config/saml2_config.py
index 9277b5f342..036f8c0e90 100644
--- a/synapse/config/saml2_config.py
+++ b/synapse/config/saml2_config.py
@@ -18,8 +18,6 @@ import logging
 from typing import Any, List
 
 import attr
-import jinja2
-import pkg_resources
 
 from synapse.python_dependencies import DependencyException, check_requirements
 from synapse.util.module_loader import load_module, load_python_module
@@ -171,15 +169,9 @@ class SAML2Config(Config):
             saml2_config.get("saml_session_lifetime", "15m")
         )
 
-        template_dir = saml2_config.get("template_dir")
-        if not template_dir:
-            template_dir = pkg_resources.resource_filename("synapse", "res/templates",)
-
-        loader = jinja2.FileSystemLoader(template_dir)
-        # enable auto-escape here, to having to remember to escape manually in the
-        # template
-        env = jinja2.Environment(loader=loader, autoescape=True)
-        self.saml2_error_html_template = env.get_template("saml_error.html")
+        self.saml2_error_html_template = self.read_templates(
+            ["saml_error.html"], saml2_config.get("template_dir")
+        )
 
     def _default_saml_config_dict(
         self, required_attributes: set, optional_attributes: set
diff --git a/synapse/config/sso.py b/synapse/config/sso.py
index 73b7296399..4427676167 100644
--- a/synapse/config/sso.py
+++ b/synapse/config/sso.py
@@ -12,11 +12,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-import os
 from typing import Any, Dict
 
-import pkg_resources
-
 from ._base import Config
 
 
@@ -29,22 +26,32 @@ class SSOConfig(Config):
     def read_config(self, config, **kwargs):
         sso_config = config.get("sso") or {}  # type: Dict[str, Any]
 
-        # Pick a template directory in order of:
-        # * The sso-specific template_dir
-        # * /path/to/synapse/install/res/templates
+        # The sso-specific template_dir
         template_dir = sso_config.get("template_dir")
-        if not template_dir:
-            template_dir = pkg_resources.resource_filename("synapse", "res/templates",)
 
-        self.sso_template_dir = template_dir
-        self.sso_account_deactivated_template = self.read_file(
-            os.path.join(self.sso_template_dir, "sso_account_deactivated.html"),
-            "sso_account_deactivated_template",
+        # Read templates from disk
+        (
+            self.sso_redirect_confirm_template,
+            self.sso_auth_confirm_template,
+            self.sso_error_template,
+            sso_account_deactivated_template,
+            sso_auth_success_template,
+        ) = self.read_templates(
+            [
+                "sso_redirect_confirm.html",
+                "sso_auth_confirm.html",
+                "sso_error.html",
+                "sso_account_deactivated.html",
+                "sso_auth_success.html",
+            ],
+            template_dir,
         )
-        self.sso_auth_success_template = self.read_file(
-            os.path.join(self.sso_template_dir, "sso_auth_success.html"),
-            "sso_auth_success_template",
+
+        # These templates have no placeholders, so render them here
+        self.sso_account_deactivated_template = (
+            sso_account_deactivated_template.render()
         )
+        self.sso_auth_success_template = sso_auth_success_template.render()
 
         self.sso_client_whitelist = sso_config.get("client_whitelist") or []
 
diff --git a/synapse/handlers/account_validity.py b/synapse/handlers/account_validity.py
index 590135d19c..b865bf5b48 100644
--- a/synapse/handlers/account_validity.py
+++ b/synapse/handlers/account_validity.py
@@ -26,11 +26,6 @@ from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.types import UserID
 from synapse.util import stringutils
 
-try:
-    from synapse.push.mailer import load_jinja2_templates
-except ImportError:
-    load_jinja2_templates = None
-
 logger = logging.getLogger(__name__)
 
 
@@ -47,9 +42,11 @@ class AccountValidityHandler(object):
         if (
             self._account_validity.enabled
             and self._account_validity.renew_by_email_enabled
-            and load_jinja2_templates
         ):
             # Don't do email-specific configuration if renewal by email is disabled.
+            self._template_html = self.config.account_validity_template_html
+            self._template_text = self.config.account_validity_template_text
+
             try:
                 app_name = self.hs.config.email_app_name
 
@@ -65,17 +62,6 @@ class AccountValidityHandler(object):
 
             self._raw_from = email.utils.parseaddr(self._from_string)[1]
 
-            self._template_html, self._template_text = load_jinja2_templates(
-                self.config.email_template_dir,
-                [
-                    self.config.email_expiry_template_html,
-                    self.config.email_expiry_template_text,
-                ],
-                apply_format_ts_filter=True,
-                apply_mxc_to_http_filter=True,
-                public_baseurl=self.config.public_baseurl,
-            )
-
             # Check the renewal emails to send and send them every 30min.
             def send_emails():
                 # run as a background process to make sure that the database transactions
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index c24e7bafe0..68d6870e40 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -42,7 +42,6 @@ from synapse.http.site import SynapseRequest
 from synapse.logging.context import defer_to_thread
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.module_api import ModuleApi
-from synapse.push.mailer import load_jinja2_templates
 from synapse.types import Requester, UserID
 from synapse.util import stringutils as stringutils
 from synapse.util.threepids import canonicalise_email
@@ -132,18 +131,17 @@ class AuthHandler(BaseHandler):
         # after the SSO completes and before redirecting them back to their client.
         # It notifies the user they are about to give access to their matrix account
         # to the client.
-        self._sso_redirect_confirm_template = load_jinja2_templates(
-            hs.config.sso_template_dir, ["sso_redirect_confirm.html"],
-        )[0]
+        self._sso_redirect_confirm_template = hs.config.sso_redirect_confirm_template
+
         # The following template is shown during user interactive authentication
         # in the fallback auth scenario. It notifies the user that they are
         # authenticating for an operation to occur on their account.
-        self._sso_auth_confirm_template = load_jinja2_templates(
-            hs.config.sso_template_dir, ["sso_auth_confirm.html"],
-        )[0]
+        self._sso_auth_confirm_template = hs.config.sso_auth_confirm_template
+
         # The following template is shown after a successful user interactive
         # authentication session. It tells the user they can close the window.
         self._sso_auth_success_template = hs.config.sso_auth_success_template
+
         # The following template is shown during the SSO authentication process if
         # the account is deactivated.
         self._sso_account_deactivated_template = (
diff --git a/synapse/handlers/oidc_handler.py b/synapse/handlers/oidc_handler.py
index fa5ee5de8f..87d28a7ae9 100644
--- a/synapse/handlers/oidc_handler.py
+++ b/synapse/handlers/oidc_handler.py
@@ -38,7 +38,6 @@ from synapse.config import ConfigError
 from synapse.http.server import respond_with_html
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import make_deferred_yieldable
-from synapse.push.mailer import load_jinja2_templates
 from synapse.types import UserID, map_username_to_mxid_localpart
 
 if TYPE_CHECKING:
@@ -123,9 +122,7 @@ class OidcHandler:
         self._hostname = hs.hostname  # type: str
         self._server_name = hs.config.server_name  # type: str
         self._macaroon_secret_key = hs.config.macaroon_secret_key
-        self._error_template = load_jinja2_templates(
-            hs.config.sso_template_dir, ["sso_error.html"]
-        )[0]
+        self._error_template = hs.config.sso_error_template
 
         # identifier for the external_ids table
         self._auth_provider_id = "oidc"
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index af117fddf9..c38e037281 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -16,8 +16,7 @@
 import email.mime.multipart
 import email.utils
 import logging
-import time
-import urllib
+import urllib.parse
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
 from typing import Iterable, List, TypeVar
@@ -640,72 +639,3 @@ def string_ordinal_total(s):
     for c in s:
         tot += ord(c)
     return tot
-
-
-def format_ts_filter(value, format):
-    return time.strftime(format, time.localtime(value / 1000))
-
-
-def load_jinja2_templates(
-    template_dir,
-    template_filenames,
-    apply_format_ts_filter=False,
-    apply_mxc_to_http_filter=False,
-    public_baseurl=None,
-):
-    """Loads and returns one or more jinja2 templates and applies optional filters
-
-    Args:
-        template_dir (str): The directory where templates are stored
-        template_filenames (list[str]): A list of template filenames
-        apply_format_ts_filter (bool): Whether to apply a template filter that formats
-            timestamps
-        apply_mxc_to_http_filter (bool): Whether to apply a template filter that converts
-            mxc urls to http urls
-        public_baseurl (str|None): The public baseurl of the server. Required for
-            apply_mxc_to_http_filter to be enabled
-
-    Returns:
-        A list of jinja2 templates corresponding to the given list of filenames,
-        with order preserved
-    """
-    logger.info(
-        "loading email templates %s from '%s'", template_filenames, template_dir
-    )
-    loader = jinja2.FileSystemLoader(template_dir)
-    env = jinja2.Environment(loader=loader)
-
-    if apply_format_ts_filter:
-        env.filters["format_ts"] = format_ts_filter
-
-    if apply_mxc_to_http_filter and public_baseurl:
-        env.filters["mxc_to_http"] = _create_mxc_to_http_filter(public_baseurl)
-
-    templates = []
-    for template_filename in template_filenames:
-        template = env.get_template(template_filename)
-        templates.append(template)
-
-    return templates
-
-
-def _create_mxc_to_http_filter(public_baseurl):
-    def mxc_to_http_filter(value, width, height, resize_method="crop"):
-        if value[0:6] != "mxc://":
-            return ""
-
-        serverAndMediaId = value[6:]
-        fragment = None
-        if "#" in serverAndMediaId:
-            (serverAndMediaId, fragment) = serverAndMediaId.split("#", 1)
-            fragment = "#" + fragment
-
-        params = {"width": width, "height": height, "method": resize_method}
-        return "%s_matrix/media/v1/thumbnail/%s?%s%s" % (
-            public_baseurl,
-            serverAndMediaId,
-            urllib.parse.urlencode(params),
-            fragment or "",
-        )
-
-    return mxc_to_http_filter
diff --git a/synapse/push/pusher.py b/synapse/push/pusher.py
index 8ad0bf5936..f626797133 100644
--- a/synapse/push/pusher.py
+++ b/synapse/push/pusher.py
@@ -15,22 +15,13 @@
 
 import logging
 
+from synapse.push.emailpusher import EmailPusher
+from synapse.push.mailer import Mailer
+
 from .httppusher import HttpPusher
 
 logger = logging.getLogger(__name__)
 
-# We try importing this if we can (it will fail if we don't
-# have the optional email dependencies installed). We don't
-# yet have the config to know if we need the email pusher,
-# but importing this after daemonizing seems to fail
-# (even though a simple test of importing from a daemonized
-# process works fine)
-try:
-    from synapse.push.emailpusher import EmailPusher
-    from synapse.push.mailer import Mailer, load_jinja2_templates
-except Exception:
-    pass
-
 
 class PusherFactory(object):
     def __init__(self, hs):
@@ -43,16 +34,8 @@ class PusherFactory(object):
         if hs.config.email_enable_notifs:
             self.mailers = {}  # app_name -> Mailer
 
-            self.notif_template_html, self.notif_template_text = load_jinja2_templates(
-                self.config.email_template_dir,
-                [
-                    self.config.email_notif_template_html,
-                    self.config.email_notif_template_text,
-                ],
-                apply_format_ts_filter=True,
-                apply_mxc_to_http_filter=True,
-                public_baseurl=self.config.public_baseurl,
-            )
+            self._notif_template_html = hs.config.email_notif_template_html
+            self._notif_template_text = hs.config.email_notif_template_text
 
             self.pusher_types["email"] = self._create_email_pusher
 
@@ -73,8 +56,8 @@ class PusherFactory(object):
             mailer = Mailer(
                 hs=self.hs,
                 app_name=app_name,
-                template_html=self.notif_template_html,
-                template_text=self.notif_template_text,
+                template_html=self._notif_template_html,
+                template_text=self._notif_template_text,
             )
             self.mailers[app_name] = mailer
         return EmailPusher(self.hs, pusherdict, mailer)
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index e5f22fb858..3250d41dde 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -78,8 +78,6 @@ CONDITIONAL_REQUIREMENTS = {
     "matrix-synapse-ldap3": ["matrix-synapse-ldap3>=0.1"],
     # we use execute_batch, which arrived in psycopg 2.7.
     "postgres": ["psycopg2>=2.7"],
-    # ConsentResource uses select_autoescape, which arrived in jinja 2.9
-    "resources.consent": ["Jinja2>=2.9"],
     # ACME support is required to provision TLS certificates from authorities
     # that use the protocol, such as Let's Encrypt.
     "acme": [
diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py
index fead85074b..203e76b9f2 100644
--- a/synapse/rest/client/v2_alpha/account.py
+++ b/synapse/rest/client/v2_alpha/account.py
@@ -32,7 +32,7 @@ from synapse.http.servlet import (
     parse_json_object_from_request,
     parse_string,
 )
-from synapse.push.mailer import Mailer, load_jinja2_templates
+from synapse.push.mailer import Mailer
 from synapse.util.msisdn import phone_number_to_msisdn
 from synapse.util.stringutils import assert_valid_client_secret, random_string
 from synapse.util.threepids import canonicalise_email, check_3pid_allowed
@@ -53,21 +53,11 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
         self.identity_handler = hs.get_handlers().identity_handler
 
         if self.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            template_html, template_text = load_jinja2_templates(
-                self.config.email_template_dir,
-                [
-                    self.config.email_password_reset_template_html,
-                    self.config.email_password_reset_template_text,
-                ],
-                apply_format_ts_filter=True,
-                apply_mxc_to_http_filter=True,
-                public_baseurl=self.config.public_baseurl,
-            )
             self.mailer = Mailer(
                 hs=self.hs,
                 app_name=self.config.email_app_name,
-                template_html=template_html,
-                template_text=template_text,
+                template_html=self.config.email_password_reset_template_html,
+                template_text=self.config.email_password_reset_template_text,
             )
 
     async def on_POST(self, request):
@@ -169,9 +159,8 @@ class PasswordResetSubmitTokenServlet(RestServlet):
         self.clock = hs.get_clock()
         self.store = hs.get_datastore()
         if self.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            (self.failure_email_template,) = load_jinja2_templates(
-                self.config.email_template_dir,
-                [self.config.email_password_reset_template_failure_html],
+            self._failure_email_template = (
+                self.config.email_password_reset_template_failure_html
             )
 
     async def on_GET(self, request, medium):
@@ -214,14 +203,14 @@ class PasswordResetSubmitTokenServlet(RestServlet):
                     return None
 
             # Otherwise show the success template
-            html = self.config.email_password_reset_template_success_html
+            html = self.config.email_password_reset_template_success_html_content
             status_code = 200
         except ThreepidValidationError as e:
             status_code = e.code
 
             # Show a failure page with a reason
             template_vars = {"failure_reason": e.msg}
-            html = self.failure_email_template.render(**template_vars)
+            html = self._failure_email_template.render(**template_vars)
 
         respond_with_html(request, status_code, html)
 
@@ -411,19 +400,11 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
         self.store = self.hs.get_datastore()
 
         if self.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            template_html, template_text = load_jinja2_templates(
-                self.config.email_template_dir,
-                [
-                    self.config.email_add_threepid_template_html,
-                    self.config.email_add_threepid_template_text,
-                ],
-                public_baseurl=self.config.public_baseurl,
-            )
             self.mailer = Mailer(
                 hs=self.hs,
                 app_name=self.config.email_app_name,
-                template_html=template_html,
-                template_text=template_text,
+                template_html=self.config.email_add_threepid_template_html,
+                template_text=self.config.email_add_threepid_template_text,
             )
 
     async def on_POST(self, request):
@@ -578,9 +559,8 @@ class AddThreepidEmailSubmitTokenServlet(RestServlet):
         self.clock = hs.get_clock()
         self.store = hs.get_datastore()
         if self.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            (self.failure_email_template,) = load_jinja2_templates(
-                self.config.email_template_dir,
-                [self.config.email_add_threepid_template_failure_html],
+            self._failure_email_template = (
+                self.config.email_add_threepid_template_failure_html
             )
 
     async def on_GET(self, request):
@@ -631,7 +611,7 @@ class AddThreepidEmailSubmitTokenServlet(RestServlet):
 
             # Show a failure page with a reason
             template_vars = {"failure_reason": e.msg}
-            html = self.failure_email_template.render(**template_vars)
+            html = self._failure_email_template.render(**template_vars)
 
         respond_with_html(request, status_code, html)
 
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index f808175698..7290fd0756 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -44,7 +44,7 @@ from synapse.http.servlet import (
     parse_json_object_from_request,
     parse_string,
 )
-from synapse.push.mailer import load_jinja2_templates
+from synapse.push.mailer import Mailer
 from synapse.util.msisdn import phone_number_to_msisdn
 from synapse.util.ratelimitutils import FederationRateLimiter
 from synapse.util.stringutils import assert_valid_client_secret, random_string
@@ -81,23 +81,11 @@ class EmailRegisterRequestTokenRestServlet(RestServlet):
         self.config = hs.config
 
         if self.hs.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            from synapse.push.mailer import Mailer, load_jinja2_templates
-
-            template_html, template_text = load_jinja2_templates(
-                self.config.email_template_dir,
-                [
-                    self.config.email_registration_template_html,
-                    self.config.email_registration_template_text,
-                ],
-                apply_format_ts_filter=True,
-                apply_mxc_to_http_filter=True,
-                public_baseurl=self.config.public_baseurl,
-            )
             self.mailer = Mailer(
                 hs=self.hs,
                 app_name=self.config.email_app_name,
-                template_html=template_html,
-                template_text=template_text,
+                template_html=self.config.email_registration_template_html,
+                template_text=self.config.email_registration_template_text,
             )
 
     async def on_POST(self, request):
@@ -262,15 +250,8 @@ class RegistrationSubmitTokenServlet(RestServlet):
         self.store = hs.get_datastore()
 
         if self.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            (self.failure_email_template,) = load_jinja2_templates(
-                self.config.email_template_dir,
-                [self.config.email_registration_template_failure_html],
-            )
-
-        if self.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            (self.failure_email_template,) = load_jinja2_templates(
-                self.config.email_template_dir,
-                [self.config.email_registration_template_failure_html],
+            self._failure_email_template = (
+                self.config.email_registration_template_failure_html
             )
 
     async def on_GET(self, request, medium):
@@ -318,7 +299,7 @@ class RegistrationSubmitTokenServlet(RestServlet):
 
             # Show a failure page with a reason
             template_vars = {"failure_reason": e.msg}
-            html = self.failure_email_template.render(**template_vars)
+            html = self._failure_email_template.render(**template_vars)
 
         respond_with_html(request, status_code, html)
 
diff --git a/tests/config/test_base.py b/tests/config/test_base.py
new file mode 100644
index 0000000000..42ee5f56d9
--- /dev/null
+++ b/tests/config/test_base.py
@@ -0,0 +1,82 @@
+# -*- coding: utf-8 -*-
+# Copyright 2020 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os.path
+import tempfile
+
+from synapse.config import ConfigError
+from synapse.util.stringutils import random_string
+
+from tests import unittest
+
+
+class BaseConfigTestCase(unittest.HomeserverTestCase):
+    def prepare(self, reactor, clock, hs):
+        self.hs = hs
+
+    def test_loading_missing_templates(self):
+        # Use a temporary directory that exists on the system, but that isn't likely to
+        # contain template files
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Attempt to load an HTML template from our custom template directory
+            template = self.hs.config.read_templates(["sso_error.html"], tmp_dir)[0]
+
+        # If no errors, we should've gotten the default template instead
+
+        # Render the template
+        a_random_string = random_string(5)
+        html_content = template.render({"error_description": a_random_string})
+
+        # Check that our string exists in the template
+        self.assertIn(
+            a_random_string,
+            html_content,
+            "Template file did not contain our test string",
+        )
+
+    def test_loading_custom_templates(self):
+        # Use a temporary directory that exists on the system
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            # Create a temporary bogus template file
+            with tempfile.NamedTemporaryFile(dir=tmp_dir) as tmp_template:
+                # Get temporary file's filename
+                template_filename = os.path.basename(tmp_template.name)
+
+                # Write a custom HTML template
+                contents = b"{{ test_variable }}"
+                tmp_template.write(contents)
+                tmp_template.flush()
+
+                # Attempt to load the template from our custom template directory
+                template = (
+                    self.hs.config.read_templates([template_filename], tmp_dir)
+                )[0]
+
+        # Render the template
+        a_random_string = random_string(5)
+        html_content = template.render({"test_variable": a_random_string})
+
+        # Check that our string exists in the template
+        self.assertIn(
+            a_random_string,
+            html_content,
+            "Template file did not contain our test string",
+        )
+
+    def test_loading_template_from_nonexistent_custom_directory(self):
+        with self.assertRaises(ConfigError):
+            self.hs.config.read_templates(
+                ["some_filename.html"], "a_nonexistent_directory"
+            )