Binding System refactor #13970
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Binding System refactor #13970
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- `ExpressionObserver` has been removed and its functionality merged with `BindingExpression` - `BindingExpression` handles all types of `BindingMode` itself; doesn't require `BindingOperations.Apply` to set up a separate observable for `TwoWay/`OneWayToSource` bindings - This allows us to fix some long-standing issues with `OneWayToSource` bindings - Expression nodes have been refactored - No longer split between `Avalonia.Base` and `Avalonia.Markup` - Categorize them according to whether they use reflection or not A few tests are failing around binding warnings: this is because the next step here is to fix binding warnings.
Null is a theoretically valid value for `Source`; setting it to null shouldn't mean "use the data context".
Previously, `CompiledBindingPathBuilder` didn't have a `TemplatedParent` method and instead the XAML compiler rewrite templated parent bindings to be a `$self.TemplateParent` property binding. resulting in extraneous logs. Add a constructor with an `apiVersion` to `CompiledBindingPathBuilder` which will be used by newer versions of the XAML compiler, and if a usage is detected using an `apiVersion` of 0, then upgrade `$self.TemplatedParent` to use a `TemplatedParentPathElement`.
...on elements which aren't yet rooted.
"Could not convert" instead of "Cannot convert".
A bit of a hack as we'd ideally not be using reflection when using compiled bindings.
Should only be used for tests.
And also use "identity equals" where value types and strings use `object.Equals` and reference types use `object.ReferenceEquals`.
Removed deleted files from csproj that were re-added due to indentation changes.
And `UntypedBindingExpressionBase`.
This matches WPF's API.
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Certain conversions rely on type converters, which were disabled in compiled bindings since #13970 due to warnings that type converters are not trimming friendly. Ideally we'd be generating the type conversion logic in the XAML compiler, but in reality the problem with type converters and trimming is limited to type converters with generics, which is an edge case. For the moment re-enable the usage of type converters in compiled bindings until we implement generating the conversion code in the XAML compiler.
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* Update ncrunch config. * Add tests for converting strings to brushes. * Make complied bindings use TypeConverters. Certain conversions rely on type converters, which were disabled in compiled bindings since #13970 due to warnings that type converters are not trimming friendly. Ideally we'd be generating the type conversion logic in the XAML compiler, but in reality the problem with type converters and trimming is limited to type converters with generics, which is an edge case. For the moment re-enable the usage of type converters in compiled bindings until we implement generating the conversion code in the XAML compiler.
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Usually it is not necessary to provide the target property when creating a `BindingExpression` because the property will be assigned when the binding expression is attached to the target in `BindingExpressionBase.Attach`. This is however one case where `Attach` is not called: when the obsolete `binding.Initiate` method is called and then an observable is read from the `InstancedBinding` without the binding actually being attached to the target object. In this case, prior to the binding refactor in #13970 the value produced by the observable was still converted to the target type. After #13970, because the target property (and hence the target type) is not yet set, the conversion is to the target type is no longer done. `DataGrid` uses this obsolete method when editing cells, causing #15081. Ideally we'd fix that in `DataGrid` but I'm not happy making this change so close to 11.1, so instead fix this use-case to behave as before. Fixes #15081
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* Added failing tests for #15081. * Provide target property in BindingExpression ctor. Usually it is not necessary to provide the target property when creating a `BindingExpression` because the property will be assigned when the binding expression is attached to the target in `BindingExpressionBase.Attach`. This is however one case where `Attach` is not called: when the obsolete `binding.Initiate` method is called and then an observable is read from the `InstancedBinding` without the binding actually being attached to the target object. In this case, prior to the binding refactor in #13970 the value produced by the observable was still converted to the target type. After #13970, because the target property (and hence the target type) is not yet set, the conversion is to the target type is no longer done. `DataGrid` uses this obsolete method when editing cells, causing #15081. Ideally we'd fix that in `DataGrid` but I'm not happy making this change so close to 11.1, so instead fix this use-case to behave as before. Fixes #15081
grokys
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When #13970 was written, [a check](https://github.com/AvaloniaUI/Avalonia/pull/13970/files#diff-cfb25a491b9452e1815aa2c0d71465aaf81e99792a88a04a1a2ed572fd1930ffR60) was added to ensure that nested `BindingNotification`s didn't happen, and the refactor was written with the assumption that they wouldn't happen. The problem is that they _do_ happen: when a source object implements both `INotifyDataErrorInfo` and had data annotations, then the nested data validation plugins would each wrap the value coming from the previous plugin in a new `BindingNotification`, resulting in nested `BindingNotifications`. This adds support for nested binding notifications back in - even though IMO nesting binding notifications is a bug, if we're doing it and we previously supported it then we should continue to support it. Fixes #15201
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* Added failing test for #15201. * Handle nested BindingNotifications. When #13970 was written, [a check](https://github.com/AvaloniaUI/Avalonia/pull/13970/files#diff-cfb25a491b9452e1815aa2c0d71465aaf81e99792a88a04a1a2ed572fd1930ffR60) was added to ensure that nested `BindingNotification`s didn't happen, and the refactor was written with the assumption that they wouldn't happen. The problem is that they _do_ happen: when a source object implements both `INotifyDataErrorInfo` and had data annotations, then the nested data validation plugins would each wrap the value coming from the previous plugin in a new `BindingNotification`, resulting in nested `BindingNotifications`. This adds support for nested binding notifications back in - even though IMO nesting binding notifications is a bug, if we're doing it and we previously supported it then we should continue to support it. Fixes #15201
grokys
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* Added failing tests for #15081. * Provide target property in BindingExpression ctor. Usually it is not necessary to provide the target property when creating a `BindingExpression` because the property will be assigned when the binding expression is attached to the target in `BindingExpressionBase.Attach`. This is however one case where `Attach` is not called: when the obsolete `binding.Initiate` method is called and then an observable is read from the `InstancedBinding` without the binding actually being attached to the target object. In this case, prior to the binding refactor in #13970 the value produced by the observable was still converted to the target type. After #13970, because the target property (and hence the target type) is not yet set, the conversion is to the target type is no longer done. `DataGrid` uses this obsolete method when editing cells, causing #15081. Ideally we'd fix that in `DataGrid` but I'm not happy making this change so close to 11.1, so instead fix this use-case to behave as before. Fixes #15081
grokys
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* Added failing test for #15201. * Handle nested BindingNotifications. When #13970 was written, [a check](https://github.com/AvaloniaUI/Avalonia/pull/13970/files#diff-cfb25a491b9452e1815aa2c0d71465aaf81e99792a88a04a1a2ed572fd1930ffR60) was added to ensure that nested `BindingNotification`s didn't happen, and the refactor was written with the assumption that they wouldn't happen. The problem is that they _do_ happen: when a source object implements both `INotifyDataErrorInfo` and had data annotations, then the nested data validation plugins would each wrap the value coming from the previous plugin in a new `BindingNotification`, resulting in nested `BindingNotifications`. This adds support for nested binding notifications back in - even though IMO nesting binding notifications is a bug, if we're doing it and we previously supported it then we should continue to support it. Fixes #15201
This was referenced Jun 24, 2024
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What does the pull request do?
A major refactor of the binding system:
BindingExpressioncode: no more separateBindingObserverandBindingExpression- everything is now implemented inBindingExpressionitselfBindingExpressionBasethat acts as a base-class for the various types of binding expressionsBindmethod onAvaloniaObjectthat returns the createdBindingExpressionBaseBindingExpressions can now be put directly into theValueStoremeaning that no intermediate wrapper objects are required, reducing memory usageBindingExpressionnow has more information about what's being bound, we can log less extraneous warnings (Error logged to output window when binding to Run.Text #9422, Binding errors are being logged even beforeDataContextis set #5762)This allows us to add a new feature in this PR and more new features in future:
UpdateSourceTrigger(Porting WPF UpdateSourceTrigger #3754)BindingExpressionBase.UpdateSourceandUpdateTargetBenchmarks
masterrefactor/bindingexpressions-in-valuestoreAs can be seen, almost all of the benchmarks have significantly better memory usage and most have better or equal performance. There are a couple of exceptions though:
Setup_TemplateBinding_OneWayandProduce_TemplateBinding_Value_OneWay.What's happening here is that we're now storing the current value from the binding as a boxed value in
TemplateBindingwhereas before anIValueEntry<T>was being created for each template binding, meaning that the value didn't need to be boxed.Setup_TemplateBinding_OneWaybeing slightly slower is a result of this: a little more GC is taking place. This is offset by the reduced memory cost for setting up aTemplateBindingafter the refactor.Breaking changes
Binding.Sourcedefault value is nowUnsetvalue- setting it to null now means "bind to null source" instead of "bind to data context" (as in WPF)FallbackValueandTargetNullValueconversion errors are no longer passed to the binding target asBindingNotifications - just logs an errorTemplateBindingnow throws if Mode is set toOneTimeorOneWayToSource- previously it silently reverted toOneWayObsoletions / Deprecations
Fixed issues
Fixes #3754
Fixes #5762
Fixes #9422
Fixes #10469
Fixes #10793
Fixes #13533
Fixes #13734