1 files changed, 12 insertions, 2 deletions
diff --git a/docs/templates.md b/docs/templates.md
index 2b66e9d862..f87692a453 100644
--- a/docs/templates.md
+++ b/docs/templates.md
@@ -36,6 +36,13 @@ Turns a `mxc://` URL for media content into an HTTP(S) one using the homeserver'
 
 Example: `message.sender_avatar_url|mxc_to_http(32,32)`
 
+```python
+localpart_from_email(address: str) -> str
+```
+
+Returns the local part of an email address (e.g. `alice` in `alice@example.com`).
+
+Example: `user.email_address|localpart_from_email`
 
 ## Email templates
 
@@ -176,8 +183,11 @@ Below are the templates Synapse will look for when generating pages related to S
              for the brand of the IdP
     * `user_attributes`: an object containing details about the user that
       we received from the IdP. May have the following attributes:
-        * display_name: the user's display_name
-        * emails: a list of email addresses
+        * `display_name`: the user's display name
+        * `emails`: a list of email addresses
+        * `localpart`: the local part of the Matrix user ID to register,
+          if `localpart_template` is set in the mapping provider configuration (empty
+          string if not)
   The template should render a form which submits the following fields:
     * `username`: the localpart of the user's chosen user id
 * `sso_new_user_consent.html`: HTML page allowing the user to consent to the