user_groups: Add endpoint to check whether a user is member of a group.

This commit adds 'GET /user_groups/{id}/members/{id}' endpoint to check
whether a user is member of a group.

This commit also adds for_read parameter to access_user_group_by_id,
which if passed as True will provide access to read user group even
if it a system group or if non-admin acting user is not part of the
group.

templates/zerver/api/changelog.md

@@ -31,6 +31,9 @@ format used by the Zulip server that they are interacting with.
   `remove_subgroups`).
 * [`PATCH /user_groups/{user_group_id}/subgroups`](/api/update-user-group-subgroups):
   Added new endpoint for updating subgroups of a user group.
+* [`GET /user_groups/{user_group_id}/members/{user_id}`](/api/get-is-user-group-member):
+  Added new endpoint for checking whether a given user is member of a
+  given user group.
 
 **Feature level 126**
 

templates/zerver/help/include/rest-endpoints.md

@@ -62,6 +62,7 @@
 * [Delete a user group](/api/remove-user-group)
 * [Update user group members](/api/update-user-group-members)
 * [Update user group subgroups](/api/update-user-group-subgroups)
+* [Get user group membership status](/api/get-is-user-group-member)
 * [Mute a user](/api/mute-user)
 * [Unmute a user](/api/unmute-user)
 

zerver/lib/user_groups.py

@@ -9,9 +9,18 @@ from zerver.lib.exceptions import JsonableError
 from zerver.models import GroupGroupMembership, Realm, UserGroup, UserGroupMembership, UserProfile
 
 
-def access_user_group_by_id(user_group_id: int, user_profile: UserProfile) -> UserGroup:
+def access_user_group_by_id(
+    user_group_id: int, user_profile: UserProfile, *, for_read: bool = False
+) -> UserGroup:
     try:
         user_group = UserGroup.objects.get(id=user_group_id, realm=user_profile.realm)
+        if for_read and not user_profile.is_guest:
+            # Everyone is allowed to read a user group and check who
+            # are its members. Guests should be unable to reach this
+            # code path, since they can't access user groups API
+            # endpoints, but we check for guests here for defense in
+            # depth.
+            return user_group
         if user_group.is_system_group:
             raise JsonableError(_("Insufficient permission"))
         group_member_ids = get_user_group_direct_members(user_group)

zerver/openapi/zulip.yaml

@@ -13975,6 +13975,44 @@ paths:
       responses:
         "200":
           $ref: "#/components/responses/SimpleSuccess"
+  /user_groups/{user_group_id}/members/{user_id}:
+    get:
+      operationId: get-is-user-group-member
+      summary: Get user group membership status
+      tags: ["users"]
+      description: |
+        Check whether a user is member of user group.
+
+        `GET {{ api_url }}/v1/user_groups/{user_group_id}/members/{user_id}`
+
+        **Changes**: New in Zulip 6.0 (feature level 127).
+      parameters:
+        - $ref: "#/components/parameters/UserGroupId"
+        - $ref: "#/components/parameters/UserId"
+        - $ref: "#/components/parameters/DirectMemberOnly"
+      responses:
+        "200":
+          description: Success
+          content:
+            application/json:
+              schema:
+                allOf:
+                  - $ref: "#/components/schemas/JsonSuccessBase"
+                  - $ref: "#/components/schemas/SuccessDescription"
+                  - additionalProperties: false
+                    properties:
+                      result: {}
+                      msg: {}
+                      is_user_group_member:
+                        type: boolean
+                        description: |
+                          Whether the user is member of user group.
+                    example:
+                      {
+                        "msg": "",
+                        "result": "success",
+                        "is_user_group_member": false,
+                      }
   /real-time:
     # This entry is a hack; it exists to give us a place to put the text
     # documenting the parameters for call_on_each_event and friends.
@@ -16320,3 +16358,13 @@ components:
         type: string
       example: https://github.com/zulip/zulip/issues/%(id)s
       required: true
+    DirectMemberOnly:
+      name: direct_member_only
+      in: query
+      description: |
+        Whether to consider only the direct members of user group and not members
+        of its subgroups. Default is `False`.
+      schema:
+        type: boolean
+      example: false
+      required: false

zerver/tests/test_user_groups.py

@@ -884,3 +884,60 @@ class UserGroupAPITestCase(UserGroupTestCase):
         # Test when nothing is provided
         result = self.client_post(f"/json/user_groups/{support_group.id}/subgroups", info={})
         self.assert_json_error(result, 'Nothing to do. Specify at least one of "add" or "delete".')
+
+    def test_get_is_user_group_member_status(self) -> None:
+        self.login("iago")
+        realm = get_realm("zulip")
+        desdemona = self.example_user("desdemona")
+        iago = self.example_user("iago")
+        othello = self.example_user("othello")
+        admins_group = UserGroup.objects.get(
+            realm=realm, name="@role:administrators", is_system_group=True
+        )
+
+        # Invalid user ID.
+        result = self.client_get(f"/json/user_groups/{admins_group.id}/members/25")
+        self.assert_json_error(result, "No such user")
+
+        # Invalid user group ID.
+        result = self.client_get(f"/json/user_groups/25/members/{iago.id}")
+        self.assert_json_error(result, "Invalid user group")
+
+        result_dict = orjson.loads(
+            self.client_get(f"/json/user_groups/{admins_group.id}/members/{othello.id}").content
+        )
+        self.assertFalse(result_dict["is_user_group_member"])
+
+        result_dict = orjson.loads(
+            self.client_get(f"/json/user_groups/{admins_group.id}/members/{iago.id}").content
+        )
+        self.assertTrue(result_dict["is_user_group_member"])
+
+        # Checking membership of not a direct member but member of a subgroup.
+        result_dict = orjson.loads(
+            self.client_get(f"/json/user_groups/{admins_group.id}/members/{desdemona.id}").content
+        )
+        self.assertTrue(result_dict["is_user_group_member"])
+
+        # Checking membership of not a direct member but member of a subgroup when passing
+        # recursive parameter as False.
+        params = {"direct_member_only": orjson.dumps(True).decode()}
+        result_dict = orjson.loads(
+            self.client_get(
+                f"/json/user_groups/{admins_group.id}/members/{desdemona.id}", info=params
+            ).content
+        )
+        self.assertFalse(result_dict["is_user_group_member"])
+
+        # Logging in with a user not part of the group.
+        self.login("hamlet")
+
+        result_dict = orjson.loads(
+            self.client_get(f"/json/user_groups/{admins_group.id}/members/{iago.id}").content
+        )
+        self.assertTrue(result_dict["is_user_group_member"])
+
+        result_dict = orjson.loads(
+            self.client_get(f"/json/user_groups/{admins_group.id}/members/{othello.id}").content
+        )
+        self.assertFalse(result_dict["is_user_group_member"])

zerver/views/user_groups.py

@@ -22,10 +22,11 @@ from zerver.lib.user_groups import (
     access_user_groups_as_potential_subgroups,
     get_direct_memberships_of_users,
     get_user_group_direct_members,
+    is_user_in_group,
     user_groups_in_realm_serialized,
 )
-from zerver.lib.users import user_ids_to_users
-from zerver.lib.validator import check_int, check_list
+from zerver.lib.users import access_user_by_id, user_ids_to_users
+from zerver.lib.validator import check_bool, check_int, check_list
 from zerver.models import UserProfile
 from zerver.views.streams import compose_views
 
@@ -217,3 +218,25 @@ def update_subgroups_of_user_group(
     data = compose_views(thunks)
 
     return json_success(request, data)
+
+
+@require_member_or_admin
+@has_request_variables
+def get_is_user_group_member(
+    request: HttpRequest,
+    user_profile: UserProfile,
+    user_group_id: int = REQ(json_validator=check_int, path_only=True),
+    user_id: int = REQ(json_validator=check_int, path_only=True),
+    direct_member_only: bool = REQ(json_validator=check_bool, default=False),
+) -> HttpResponse:
+    user_group = access_user_group_by_id(user_group_id, user_profile, for_read=True)
+    target_user = access_user_by_id(user_profile, user_id, for_admin=False)
+
+    return json_success(
+        request,
+        data={
+            "is_user_group_member": is_user_in_group(
+                user_group, target_user, direct_member_only=direct_member_only
+            )
+        },
+    )

zproject/urls.py

@@ -176,6 +176,7 @@ from zerver.views.user_groups import (
     add_user_group,
     delete_user_group,
     edit_user_group,
+    get_is_user_group_member,
     get_user_group,
     update_subgroups_of_user_group,
     update_user_group_backend,
@@ -374,6 +375,9 @@ v1_api_and_json_patterns = [
     rest_path("user_groups/<int:user_group_id>", PATCH=edit_user_group, DELETE=delete_user_group),
     rest_path("user_groups/<int:user_group_id>/members", POST=update_user_group_backend),
     rest_path("user_groups/<int:user_group_id>/subgroups", POST=update_subgroups_of_user_group),
+    rest_path(
+        "user_groups/<int:user_group_id>/members/<int:user_id>", GET=get_is_user_group_member
+    ),
     # users/me -> zerver.views.user_settings
     rest_path("users/me/avatar", POST=set_avatar_backend, DELETE=delete_avatar_backend),
     # users/me/hotspots -> zerver.views.hotspots