Prevent unnecessary remounts of fragments in 'if' directives - #152
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This release includes the following features: * Support for template refs (#140) * Hot reloading of components (#146) And the following fixes and improvements: * Prevent unnecessary remounts of elements (#152) * Remove the need for a wrapping template element around dynamic slot content (#147) * Keep elements ordered properly (#155 , #156) * [PySide] Improve interaction with PySide elements (#151) * [PySide] Improve resilience of PySide in light of exceptions (#154)
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Root Cause
The issue is in ControlFlowFragment.update_fragment() at collagraph/fragment.py:445-454. When the active_child watcher triggers (because a reactive dependency changed), the callback always unmounts and remounts the fragment, even when new is old (same fragment).
The added check in fragments.py prevents the unnecessary unmount/remount cycle when the selected fragment hasn't actually changed.
Why This Happens
The observ watcher with deep=True calls the callback whenever dependencies change (see watcher.py:263: if self.deep or ...), regardless of whether the returned value changed. The fix correctly short-circuits when new is old.