Clean up the user directory sample config section (#9385)

The user directory sample config section was a little messy, and didn't adhere to our [recommended config format guidelines](https://github.com/matrix-org/synapse/blob/develop/docs/code_style.md#configuration-file-format).

This PR cleans that up a bit.

3 files changed, 67 insertions, 50 deletions

diff --git a/changelog.d/9385.feature b/changelog.d/9385.feature
new file mode 100644
index 0000000000..cbe3922de8
--- /dev/null
+++ b/changelog.d/9385.feature
@@ -0,0 +1 @@
+ Add a configuration option, `user_directory.prefer_local_users`, which when enabled will make it more likely for users on the same server as you to appear above other users.
\ No newline at end of file
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index c660c62620..4dbef41b7e 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -2544,24 +2544,35 @@ spam_checker:
 
 # User Directory configuration
 #
-# 'enabled' defines whether users can search the user directory. If
-# false then empty responses are returned to all queries. Defaults to
-# true.
-#
-# 'search_all_users' defines whether to search all users visible to your HS
-# when searching the user directory, rather than limiting to users visible
-# in public rooms.  Defaults to false.  If you set it True, you'll have to
-# rebuild the user_directory search indexes, see
-# https://github.com/matrix-org/synapse/blob/master/docs/user_directory.md
-#
-# 'prefer_local_users' defines whether to prioritise local users in
-# search query results. If True, local users are more likely to appear above
-# remote users when searching the user directory. Defaults to false.
-#
-#user_directory:
-#  enabled: true
-#  search_all_users: false
-#  prefer_local_users: false
+user_directory:
+    # Defines whether users can search the user directory. If false then
+    # empty responses are returned to all queries. Defaults to true.
+    #
+    # Uncomment to disable the user directory.
+    #
+    #enabled: false
+
+    # Defines whether to search all users visible to your HS when searching
+    # the user directory, rather than limiting to users visible in public
+    # rooms. Defaults to false.
+    #
+    # If you set it true, you'll have to rebuild the user_directory search
+    # indexes, see:
+    # https://github.com/matrix-org/synapse/blob/master/docs/user_directory.md
+    #
+    # Uncomment to return search results containing all known users, even if that
+    # user does not share a room with the requester.
+    #
+    #search_all_users: true
+
+    # Defines whether to prefer local users in search query results.
+    # If True, local users are more likely to appear above remote users
+    # when searching the user directory. Defaults to false.
+    #
+    # Uncomment to prefer local over remote users in user directory search
+    # results.
+    #
+    #prefer_local_users: true
 
 
 # User Consent configuration
diff --git a/synapse/config/user_directory.py b/synapse/config/user_directory.py
index 89dbebd148..8d05ef173c 100644
--- a/synapse/config/user_directory.py
+++ b/synapse/config/user_directory.py
@@ -24,41 +24,46 @@ class UserDirectoryConfig(Config):
     section = "userdirectory"
 
     def read_config(self, config, **kwargs):
-        self.user_directory_search_enabled = True
-        self.user_directory_search_all_users = False
-        self.user_directory_search_prefer_local_users = False
-        user_directory_config = config.get("user_directory", None)
-        if user_directory_config:
-            self.user_directory_search_enabled = user_directory_config.get(
-                "enabled", True
-            )
-            self.user_directory_search_all_users = user_directory_config.get(
-                "search_all_users", False
-            )
-            self.user_directory_search_prefer_local_users = user_directory_config.get(
-                "prefer_local_users", False
-            )
+        user_directory_config = config.get("user_directory") or {}
+        self.user_directory_search_enabled = user_directory_config.get("enabled", True)
+        self.user_directory_search_all_users = user_directory_config.get(
+            "search_all_users", False
+        )
+        self.user_directory_search_prefer_local_users = user_directory_config.get(
+            "prefer_local_users", False
+        )
 
     def generate_config_section(self, config_dir_path, server_name, **kwargs):
         return """
         # User Directory configuration
         #
-        # 'enabled' defines whether users can search the user directory. If
-        # false then empty responses are returned to all queries. Defaults to
-        # true.
-        #
-        # 'search_all_users' defines whether to search all users visible to your HS
-        # when searching the user directory, rather than limiting to users visible
-        # in public rooms.  Defaults to false.  If you set it True, you'll have to
-        # rebuild the user_directory search indexes, see
-        # https://github.com/matrix-org/synapse/blob/master/docs/user_directory.md
-        #
-        # 'prefer_local_users' defines whether to prioritise local users in
-        # search query results. If True, local users are more likely to appear above
-        # remote users when searching the user directory. Defaults to false.
-        #
-        #user_directory:
-        #  enabled: true
-        #  search_all_users: false
-        #  prefer_local_users: false
+        user_directory:
+            # Defines whether users can search the user directory. If false then
+            # empty responses are returned to all queries. Defaults to true.
+            #
+            # Uncomment to disable the user directory.
+            #
+            #enabled: false
+
+            # Defines whether to search all users visible to your HS when searching
+            # the user directory, rather than limiting to users visible in public
+            # rooms. Defaults to false.
+            #
+            # If you set it true, you'll have to rebuild the user_directory search
+            # indexes, see:
+            # https://github.com/matrix-org/synapse/blob/master/docs/user_directory.md
+            #
+            # Uncomment to return search results containing all known users, even if that
+            # user does not share a room with the requester.
+            #
+            #search_all_users: true
+
+            # Defines whether to prefer local users in search query results.
+            # If True, local users are more likely to appear above remote users
+            # when searching the user directory. Defaults to false.
+            #
+            # Uncomment to prefer local over remote users in user directory search
+            # results.
+            #
+            #prefer_local_users: true
         """