Fix SelectCurrent update before #label is composed

src/textual/widgets/_select.py

@@ -253,13 +253,17 @@ def update(self, label: RenderableType | NoSelection) -> None:
         """
         self.label = label
         self.has_value = label is not Select.NULL
-        self.query_one("#label", Static).update(
-            self.placeholder if isinstance(label, NoSelection) else label
-        )
+        try:
+            self.query_one("#label", Static).update(
+                self.placeholder if isinstance(label, NoSelection) else label
+            )
+        except NoMatches:
+            pass
 
     def compose(self) -> ComposeResult:
         """Compose label and down arrow."""
-        yield NonSelectableStatic(self.placeholder, id="label")
+        label = self.placeholder if isinstance(self.label, NoSelection) else self.label
+        yield NonSelectableStatic(label, id="label")
         yield NonSelectableStatic("▼", classes="arrow down-arrow")
         yield NonSelectableStatic("▲", classes="arrow up-arrow")
 

tests/select/test_mount_crash.py

@@ -0,0 +1,24 @@
+import pytest
+import asyncio
+
+from textual.app import App
+from textual.widgets import Select
+
+SELECT_OPTIONS = [(str(n), n) for n in range(3)]
+
+from textual.widgets._select import SelectCurrent
+
+async def test_select_current_update_before_mount():
+    """Test that updating SelectCurrent before mount does not crash."""
+    app = App()
+    async with app.run_test():
+        select_current = SelectCurrent("placeholder")
+        # Update before it is mounted / composed
+        select_current.update("new label")
+
+        # After mounting, the label should reflect the updated value
+        app.mount(select_current)
+        await app.workers.wait_for_complete()
+
+        # Wait for the next tick to ensure label is updated
+        # (Though we might need to check if label text is correct)