home: Remove now-unnecessary page_params_core_fields duplication.

Also, we update the documentation to make the overall system a bit
clearer.

Fixes #4628.

docs/events-system.md

@@ -236,6 +236,9 @@ checking that all the calls to `send_event` are covered.  Someday
 we'll add automation that verifies this directly by inspecting the
 coverage data.
 
+In the Zulip webapp, the data returned by the `register` API is
+available via the `page_params` parameter.
+
 ### Messages
 
 One exception to the protocol described in the last section is the

docs/new-feature-tutorial.md

@@ -191,8 +191,8 @@ initial state. Subsequently, clients subscribe to "events," which can
 (among other things) indicate that settings have changed. For the
 backend piece, we will need our action to make a call to `send_event`
 to send the event to clients that are active. We will also need to
-modify `fetch_initial_state_data` so that future clients see the new
+modify `fetch_initial_state_data` so that the new field is passed to
-changes.  See [our event system docs](events-system.html) for all the
+clients.  See [our event system docs](events-system.html) for all the
 gory details.
 
 Anyway, getting back to implementation details...
@@ -258,9 +258,14 @@ to explicitly update this field and send an event.
 
 ### Update application state
 
-You then need to add code that will handle the event and update the
+You then need to add code to ensure that your new setting is included
-application state. The `fetch_initial_state` and `apply_event`
+in the data sent down to clients, both when a new client is loaded,
-functions in `zerver/lib/events.py` do this.
+and when changes happen. The `fetch_initial_state_data` function is
+responsible for the former (data added to the `state` here will be
+available both in `page_params` in the browser, as well as to API
+clients like the mobile apps).  The `apply_event` function in
+`zerver/lib/events.py` is important for making sure the `state` is
+always correct, even in the event of rare race conditions.
 
     # zerver/lib/events.py
 
@@ -283,11 +288,12 @@ functions in `zerver/lib/events.py` do this.
 
 If you are adding a realm property that fits the `property_types`
 framework, you don't need to change `fetch_initial_state_data` or
-`apply_event` because there is already code to get the initial data and
+`apply_event` because there is already code to get the initial data
-the realm update event type. However, if you are adding a property
+and handle the realm update event type. However, if you are adding a
-that is handled separately, you will need to  explicitly add the property
+property that is handled separately, you will need to explicitly add
-to the `state` dictionary in the `fetch_initial_state_data` function.
+the property to the `state` dictionary in the
-Ex, for `authentication_methods`:
+`fetch_initial_state_data` function.  E.g., for
+`authentication_methods`:
 
     def fetch_initial_state_data(user_profile, event_types, queue_id, include_subscribers=True):
       # ...
@@ -298,8 +304,8 @@ Ex, for `authentication_methods`:
 
 For this setting, one won't need to change `apply_event` since its
 default code for `realm` event types handles this case correctly, but
-for a totally new type of feature, usually a few lines in that
+for a totally new type of feature, a few lines in that function may be
-function are needed.
+needed.
 
 ### Add a new view
 
@@ -311,19 +317,6 @@ already a view that does this for related flags: `update_realm` in
 `zerver/views/realm.py`. So in this case, we can add our code to the
 existing view instead of creating a new one.
 
-First, add the new feature to the `page_params_core_fields` list
-in `zerver/views/home.py`.
-
-    def home_real(request):
-      # ...
-      page_params_core_fields = [
-        # ...
-        'realm_icon_url',
-        'realm_invite_by_admins_only',
-        'realm_inline_image_preview',
-        # ...
-      )
-
 Since this feature adds a checkbox to the admin page and a new property
 to the Realm model that can be modified from there, you need to add a
 parameter for the new field to the `update_realm` function in

zerver/tests/test_home.py

@@ -48,6 +48,7 @@ class HomeTest(ZulipTestCase):
             "avatar_url_medium",
             "can_create_streams",
             "cross_realm_bots",
+            "custom_profile_fields",
             "debug_mode",
             "default_desktop_notifications",
             "default_language",

zerver/views/home.py

@@ -220,87 +220,10 @@ def home_real(request):
         has_mobile_devices    = num_push_devices_for_user(user_profile) > 0,
     )
 
-    # These fields will be automatically copied from register_ret into
+    undesired_register_ret_fields = [
-    # page_params.  It is a goal to move more of the page_params list
+        'streams',
-    # into this sort of cleaner structure.
-    page_params_core_fields = [
-        'alert_words',
-        'attachments',
-        'autoscroll_forever',
-        'avatar_source',
-        'avatar_url',
-        'avatar_url_medium',
-        'can_create_streams',
-        'default_desktop_notifications',
-        'default_language',
-        'email',
-        'emoji_alt_code',
-        'emojiset',
-        'emojiset_choices',
-        'enable_desktop_notifications',
-        'enable_digest_emails',
-        'enable_offline_email_notifications',
-        'enable_offline_push_notifications',
-        'enable_online_push_notifications',
-        'enable_sounds',
-        'enable_stream_desktop_notifications',
-        'enable_stream_sounds',
-        'enter_sends',
-        'full_name',
-        'hotspots',
-        'is_admin',
-        'last_event_id',
-        'left_side_userlist',
-        'max_icon_file_size',
-        'max_message_id',
-        'muted_topics',
-        'never_subscribed',
-        'pm_content_in_desktop_notifications',
-        'pointer',
-        'presences',
-        'queue_id',
-        'realm_add_emoji_by_admins_only',
-        'realm_allow_message_editing',
-        'realm_authentication_methods',
-        'realm_bot_domain',
-        'realm_bots',
-        'realm_create_stream_by_admins_only',
-        'realm_default_language',
-        'realm_default_streams',
-        'realm_domains',
-        'realm_email_changes_disabled',
-        'realm_emoji',
-        'realm_filters',
-        'realm_icon_source',
-        'realm_icon_url',
-        'realm_invite_by_admins_only',
-        'realm_inline_image_preview',
-        'realm_inline_url_embed_preview',
-        'realm_invite_required',
-        'realm_is_zephyr_mirror_realm',
-        'realm_mandatory_topics',
-        'realm_message_content_edit_limit_seconds',
-        'realm_message_retention_days',
-        'realm_name',
-        'realm_description',
-        'realm_name_changes_disabled',
-        'realm_password_auth_enabled',
-        'realm_presence_disabled',
-        'realm_restricted_to_domain',
-        'realm_show_digest_email',
-        'realm_uri',
-        'realm_users',
-        'realm_waiting_period_threshold',
-        'referrals',
-        'subscriptions',
-        'unsubscribed',
-        'timezone',
-        'twenty_four_hour_time',
-        'user_id',
-        'zulip_version',
     ]
-
+    for field_name in set(register_ret.keys()) - set(undesired_register_ret_fields):
-    for field_name in page_params_core_fields:
         page_params[field_name] = register_ret[field_name]
 
     if narrow_stream is not None: