Walrusify the code (#422)

src/cleo/application.py

@@ -247,9 +247,7 @@ def get_namespaces(self) -> list[str]:
         return namespaces
 
     def find_namespace(self, namespace: str) -> str:
-        all_namespaces = self.get_namespaces()
-
-        if namespace not in all_namespaces:
+        if namespace not in (all_namespaces := self.get_namespaces()):
             raise CleoNamespaceNotFoundError(namespace, all_namespaces)
 
         return namespace

src/cleo/descriptors/text_descriptor.py

@@ -160,8 +160,7 @@ def _describe_application(self, application: Application, **options: Any) -> Non
         described_namespace = options.get("namespace")
         description = ApplicationDescription(application, namespace=described_namespace)
 
-        help_text = application.help
-        if help_text:
+        if help_text := application.help:
             self._write(f"{help_text}\n\n")
 
         self._write("<b>Usage:</b>\n")
@@ -271,9 +270,7 @@ def _get_column_width(self, commands: Sequence[Command | str]) -> int:
         return max(widths) + 2
 
     def _get_command_aliases_text(self, command: Command) -> str:
-        aliases = command.aliases
-
-        if aliases:
+        if aliases := command.aliases:
             return f"[{ '|'.join(aliases) }] "
 
         return ""

src/cleo/events/event_dispatcher.py

@@ -20,9 +20,7 @@ def dispatch(self, event: Event, event_name: str | None = None) -> Event:
         if event_name is None:
             event_name = type(event).__name__
 
-        listeners = cast("list[Listener]", self.get_listeners(event_name))
-
-        if listeners:
+        if listeners := cast("list[Listener]", self.get_listeners(event_name)):
             self._do_dispatch(listeners, event_name, event)
 
         return event

src/cleo/ui/exception_trace/component.py

@@ -239,8 +239,7 @@ def ignore_files_in(self, ignore: str) -> ExceptionTrace:
 
     def render(self, io: IO | Output, simple: bool = False) -> None:
         # If simple rendering wouldn't show anything useful, abandon it.
-        simple_string = str(self._exception) if simple else ""
-        if simple_string:
+        if simple_string := str(self._exception) if simple else "":
             io.write_line("")
             io.write_line(f"<error>{simple_string}</error>")
         else: