api: Improve encoding of stream/topic max field lengths.

Previously, you had to request the `stream` event type in order to get
the stream-level parameters; this was a bad design in part because the
`subscription` event type has similar data and is preferred by most
clients.

So we move these to the `realm` object.  We also add the maximum topic
length, as an adjacent parameter.

While changing this, we also fix these to better match the names of
similar API parameters.

static/js/subs.js

@@ -627,8 +627,8 @@ export function setup_page(callback) {
         const template_data = {
             can_create_streams: page_params.can_create_streams,
             hide_all_streams: !should_list_all_streams(),
-            max_name_length: page_params.stream_name_max_length,
-            max_description_length: page_params.stream_description_max_length,
+            max_name_length: page_params.max_stream_name_length,
+            max_description_length: page_params.max_stream_description_length,
             is_owner: page_params.is_owner,
             stream_privacy_policy_values: stream_data.stream_privacy_policy_values,
             stream_post_policy_values: stream_data.stream_post_policy_values,

templates/zerver/api/changelog.md

@@ -10,6 +10,13 @@ below features are supported.
 
 ## Changes in Zulip 4.0
 
+**Feature level 53**
+
+* [`POST /register`](/api/register-queue): Added `max_topic_length`
+  and renamed `max_stream_name_length` and
+  `max_stream_description_length` to allow clients to transparently
+  support these values changing in a future server version.
+
 **Feature level 52**
 
 * `PATCH /realm`: Removed unnecessary JSON-encoding of string

version.py

@@ -30,7 +30,7 @@ DESKTOP_WARNING_VERSION = "5.2.0"
 #
 # Changes should be accompanied by documentation explaining what the
 # new level means in templates/zerver/api/changelog.md.
-API_FEATURE_LEVEL = 52
+API_FEATURE_LEVEL = 53
 
 # Bump the minor PROVISION_VERSION to indicate that folks should provision
 # only when going from an old version of the code to a newer version. Bump

zerver/lib/events.py

@@ -49,6 +49,7 @@ from zerver.lib.user_mutes import get_user_mutes
 from zerver.lib.user_status import get_user_info_dict
 from zerver.lib.users import get_cross_realm_dicts, get_raw_user_data, is_administrator_role
 from zerver.models import (
+    MAX_TOPIC_NAME_LENGTH,
     Client,
     CustomProfileField,
     Message,
@@ -250,6 +251,10 @@ def fetch_initial_state_data(
         else:
             state["realm_signup_notifications_stream_id"] = -1
 
+        state["max_stream_name_length"] = Stream.MAX_NAME_LENGTH
+        state["max_stream_description_length"] = Stream.MAX_DESCRIPTION_LENGTH
+        state["max_topic_length"] = MAX_TOPIC_NAME_LENGTH
+
     if want("realm_domains"):
         state["realm_domains"] = get_realm_domains(realm)
 
@@ -415,8 +420,6 @@ def fetch_initial_state_data(
                 # be used when the mobile apps support logged-out
                 # access.
                 state["streams"] = get_web_public_streams(realm)  # nocoverage
-        state["stream_name_max_length"] = Stream.MAX_NAME_LENGTH
-        state["stream_description_max_length"] = Stream.MAX_DESCRIPTION_LENGTH
     if want("default_streams"):
         if settings_user.is_guest:
             # Guest users and logged-out users don't have access to

zerver/openapi/zulip.yaml

@@ -6885,6 +6885,41 @@ paths:
                           **Deprecated**: This field may be removed in future versions as it no
                           longer has a clear purpose.  Clients wishing to fetch the latest messages
                           should pass `anchor="latest"` to `GET /messages`.
+                      max_stream_name_length:
+                        type: integer
+                        description: |
+                          Present if `realm` is present in `fetch_event_types`.
+
+                          The maximum allowed length for a stream name.  Clients should use
+                          these properties rather than hardcoding field sizes, as they may
+                          change in a future Zulip release.
+
+                          **Changes**: New in Zulip 4.0 (feature level 53).  Previously,
+                          this required `stream` in `fetch_event_types`, was called
+                          `stream_name_max_length`, and always had value 60.
+                      max_stream_description_length:
+                        type: integer
+                        description: |
+                          Present if `realm` is present in `fetch_event_types`.
+
+                          The maximum allowed length for a stream description.  Clients should use
+                          these properties rather than hardcoding field sizes, as they may
+                          change in a future Zulip release.
+
+                          **Changes**: New in Zulip 4.0 (feature level 53).  Previously,
+                          this required `stream` in `fetch_event_types`, was called
+                          `stream_description_max_length`, and always had value 1024.
+                      max_topic_length:
+                        type: integer
+                        description: |
+                          Present if `realm` is present in `fetch_event_types`.
+
+                          The maximum allowed length for a topic.  Clients should use
+                          these properties rather than hardcoding field sizes, as they may
+                          change in a future Zulip release.
+
+                          **Changes**: New in Zulip 4.0 (feature level 53).  Previously,
+                          this always had value 60.
                       muted_topics:
                         type: array
                         description: |
@@ -7303,22 +7338,6 @@ paths:
 
                           For organization administrators, this will include all private streams
                           in the organization.
-                      stream_name_max_length:
-                        type: integer
-                        description: |
-                          Present if `stream` is present in `fetch_event_types`.
-
-                          The maximum allowed length for a stream name.  Clients should use
-                          these properties rather than hardcoding field sizes, as they may
-                          change in a future Zulip release.
-                      stream_description_max_length:
-                        type: integer
-                        description: |
-                          Present if `stream` is present in `fetch_event_types`.
-
-                          The maximum allowed length for a stream description.  Clients should use
-                          these properties rather than hardcoding field sizes, as they may
-                          change in a future Zulip release.
                       realm_default_streams:
                         type: array
                         items:

zerver/tests/test_home.py

@@ -106,6 +106,9 @@ class HomeTest(ZulipTestCase):
         "max_icon_file_size",
         "max_logo_file_size",
         "max_message_id",
+        "max_stream_description_length",
+        "max_stream_name_length",
+        "max_topic_length",
         "message_content_in_email_notifications",
         "muted_topics",
         "muted_users",
@@ -206,8 +209,6 @@ class HomeTest(ZulipTestCase):
         "starred_message_counts",
         "starred_messages",
         "stop_words",
-        "stream_description_max_length",
-        "stream_name_max_length",
         "subscriptions",
         "test_suite",
         "timezone",