Ensure watcher isn't called on first_set when init is False and value doesn't change (#1367)

* Ensure watcher not called when value doesnt change, even on first set

* Update CHANGELOG.md

Author: darrenburns

CHANGELOG.md

@@ -15,6 +15,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Added `textual.actions.SkipAction` exception which can be raised from an action to allow parents to process bindings.
 
+### Fixed
+
+- Fixed watch method incorrectly running on first set when value hasnt changed and init=False https://github.com/Textualize/textual/pull/1367
+
 ## [0.7.0] - 2022-12-17
 
 ### Added
@@ -34,6 +38,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fixed validator not running on first reactive set https://github.com/Textualize/textual/pull/1359
 - Ensure only printable characters are used as key_display https://github.com/Textualize/textual/pull/1361
 
+
 ## [0.6.0] - 2022-12-11
 
 ### Added

src/textual/reactive.py

@@ -175,15 +175,11 @@ def __set__(self, obj: Reactable, value: ReactiveType) -> None:
         current_value = getattr(obj, name)
         # Check for validate function
         validate_function = getattr(obj, f"validate_{name}", None)
-        # Check if this is the first time setting the value
-        first_set = getattr(obj, f"__first_set_{self.internal_name}", True)
         # Call validate
         if callable(validate_function):
             value = validate_function(value)
         # If the value has changed, or this is the first time setting the value
-        if current_value != value or first_set or self._always_update:
-            # Set the first set flag to False
-            setattr(obj, f"__first_set_{self.internal_name}", False)
+        if current_value != value or self._always_update:
             # Store the internal value
             setattr(obj, self.internal_name, value)
             # Check all watchers
@@ -200,7 +196,6 @@ def _check_watchers(cls, obj: Reactable, name: str, old_value: Any):
             obj (Reactable): The reactable object.
             name (str): Attribute name.
             old_value (Any): The old (previous) value of the attribute.
-            first_set (bool, optional): True if this is the first time setting the value. Defaults to False.
         """
         _rich_traceback_omit = True
         # Get the current value.

tests/test_reactive.py

@@ -88,8 +88,6 @@ async def watch_count(self, old_value: int, new_value: int) -> None:
     assert app.watcher_new_value == OLD_VALUE  # The value wasn't changed
 
 
-@pytest.mark.xfail(
-    reason="Reactive watcher is incorrectly always called the first time it is set, even if value is same [issue#1230]")
 async def test_watch_init_false_always_update_false():
     class WatcherInitFalse(App):
         count = reactive(0, init=False)
@@ -102,6 +100,10 @@ def watch_count(self, new_value: int) -> None:
     async with app.run_test():
         app.count = 0  # Value hasn't changed, and always_update=False, so watch_count shouldn't run
         assert app.watcher_call_count == 0
+        app.count = 0
+        assert app.watcher_call_count == 0
+        app.count = 1
+        assert app.watcher_call_count == 1
 
 
 async def test_watch_init_true():