Merge pull request #1195 from davep/button-variant-check

Check button variant for validity during button construction

Author: willmcgugan

CHANGELOG.md

@@ -31,6 +31,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Watchers are now called immediately when setting the attribute if they are synchronous. https://github.com/Textualize/textual/pull/1145
 - Widget.call_later has been renamed to Widget.call_after_refresh.
+- Button variant values are now checked at runtime. https://github.com/Textualize/textual/issues/1189
 
 ### Fixed
 

src/textual/widgets/_button.py

@@ -186,7 +186,7 @@ def __init__(
         if disabled:
             self.add_class("-disabled")
 
-        self.variant = variant
+        self.variant = self.validate_variant(variant)
 
     label: Reactive[RenderableType] = Reactive("")
     variant = Reactive.init("default")