Merge pull request #4313 from davep/bug/4248/click-markup-crash

Fix a crash in `run_action` when an action is an empty tuple

Author: willmcgugan

src/textual/app.py

@@ -3006,11 +3006,18 @@ async def _broker_event(
             return False
         else:
             event.stop()
-        if isinstance(action, (str, tuple)):
+        if isinstance(action, str) or (isinstance(action, tuple) and len(action) == 2):
             await self.run_action(action, default_namespace=default_namespace)  # type: ignore[arg-type]
         elif callable(action):
             await action()
         else:
+            if isinstance(action, tuple) and self.debug:
+                # It's a tuple and made it this far, which means it'll be a
+                # malformed action. This is a no-op, but let's log that
+                # anyway.
+                log.warning(
+                    f"Can't parse @{event_name} action from style meta; check your console markup syntax"
+                )
             return False
         return True
 

tests/test_issue_4248.py

@@ -0,0 +1,46 @@
+"""Test https://github.com/Textualize/textual/issues/4248"""
+
+from textual.app import App, ComposeResult
+from textual.widgets import Label
+
+
+async def test_issue_4248() -> None:
+    """Various forms of click parameters should be fine."""
+
+    bumps = 0
+
+    class ActionApp(App[None]):
+
+        def compose(self) -> ComposeResult:
+            yield Label("[@click]click me and crash[/]", id="nothing")
+            yield Label("[@click=]click me and crash[/]", id="no-params")
+            yield Label("[@click=()]click me and crash[/]", id="empty-params")
+            yield Label("[@click=foobar]click me[/]", id="unknown-sans-parens")
+            yield Label("[@click=foobar()]click me[/]", id="unknown-with-parens")
+            yield Label("[@click=bump]click me[/]", id="known-sans-parens")
+            yield Label("[@click=bump()]click me[/]", id="known-empty-parens")
+            yield Label("[@click=bump(100)]click me[/]", id="known-with-param")
+
+        def action_bump(self, by_value: int = 1) -> None:
+            nonlocal bumps
+            bumps += by_value
+
+    app = ActionApp()
+    async with app.run_test() as pilot:
+        assert bumps == 0
+        await pilot.click("#nothing")
+        assert bumps == 0
+        await pilot.click("#no-params")
+        assert bumps == 0
+        await pilot.click("#empty-params")
+        assert bumps == 0
+        await pilot.click("#unknown-sans-parens")
+        assert bumps == 0
+        await pilot.click("#unknown-with-parens")
+        assert bumps == 0
+        await pilot.click("#known-sans-parens")
+        assert bumps == 1
+        await pilot.click("#known-empty-parens")
+        assert bumps == 2
+        await pilot.click("#known-with-param")
+        assert bumps == 102