Epic: Add new SetBinding API for defining "compiled" bindings in code

[simonrozsival]

We agreed to implement a new public API to allow creating "compiled" bindings (TypedBinding<TSource, TProperty>) in code via source-generators and interceptors based on the proposal #20574 (see Alternative design).

• Introduce new public method BindableObjectExtensions.SetBinding<TSource, TProperty>(BindableProperty property, Func<TSource, TProperty> getter, ...) as defined in the proposal
• Create a new source generator
  • Intercept calls to SetBinding<TSource, TProperty>(...)
  • Parse getter lambda expression
    • Implement support for properties
    • Implement support for indexers
    • Implement support for as-casts
    • Implement support for C-style casts
    • Implement support for conditional access to members
    • Implement diagnostics reporting
    • Build cacheable data model
  • Generate setter from the getter lambda
  • Generate handlers array from the getter lambda
• Enable the source generator by default in MAUI apps
  • Introduce a feature switch to disable the source generator
• Add unit tests for correct caching of the generated code
• Run benchmarks comparing reflection-based binding, source-generated binding, and hand-written typed binding
• Write docs/developer guide - tracked in .NET MAUI 9: Compiled bindings can be used with C# markup docs-maui#2304

Possible future improvements

• Replace usage of TypedBinding.ForSingleNestingLevel(...) with the source generated interceptors - [Binding SG] Dogfood binding source generator in the MAUI codebase #23393
• Implement support for generic parameters
• Use the new overload in existing unit tests
• Add more public methods that could be intercepted (this has not been discussed/agreed on yet) - [Binding SG] Add an API for creating instances of TypedBinding #23239
  • for example:
    • BindingBase Binding.Create<TSource, TProperty>(Func<TSource, TProperty> getter, ...)
    • TBindable Bind<TBindable, TSource, TProperty>(this TBindable bindableObject, Func<TSource, TProperty> getter, ...) where TBindable : BindableObject.
• Improve efficiency by grouping calls to SetBinding with the same getter signature into one interceptor
• Split individual generated methods into separate files for more granular caching - [Binding SG] Split bindings source generated code into multiple files #23116
• Explore the option of resolving method groups instead of just lambda expressions
• Use roslyn-sdk test library

[github-actions]

Hi I'm an AI powered bot that finds similar issues based off the issue title.

Please view the issues below to see if they solve your problem, and if the issue describes your problem please consider closing this one and thumbs upping the other issue to help us prioritize it. Thank you!

Open similar issues:

• [Proposal] Add a new public API to allow defining TypedBinding in code (#19912), similarity score: 0.75
• [Proposal] Compiling typed bindings using source generators (#20574), similarity score: 0.74

Note: You can give me feedback by thumbs upping or thumbs downing this comment.

[AmrAlSayed0]

In this proposal #20574, the generated method StudentFirstNameBinding could benefit from being generic. So instead of this

partial class StudentDetailPage
{
    private static BindingBase StudentFirstNameBinding(
        object? source = null,
        BindingMode mode = BindingMode.OneWay, // default value based on the attribute value
        IValueConverter? converter = null,
        object? converterParameter = null,
        string? stringFormat = null,
        object? targetNullValue = null,
        object? fallbackValue = null)
        => ...;
}

it would be this

partial class StudentDetailPage
{
    private static BindingBase StudentFirstNameBinding<TSource, TProperty>(
        TSource? source = null,
        BindingMode mode = BindingMode.OneWay, // default value based on the attribute value
        IValueConverter? converter = null,
        object? converterParameter = null,
        [System.Diagnostics.CodeAnalysis.StringSyntax] string? stringFormat = null,
        TProperty? targetNullValue = null,
        TProperty? fallbackValue = null)
        => ...;
}

Same thing with SetBinding

public static partial class BindableObjectExtensions
{
    public static void SetBinding<TSource, TProperty>(
        this TSource self,
        BindableProperty property,
        Func<TSource, TProperty> getter,
        Action<TSource, TProperty>? setter = null,
	BindingMode mode = BindingMode.Default,
	IValueConverter? converter = null,
	object? converterParameter = null,
	[System.Diagnostics.CodeAnalysis.StringSyntax] string? stringFormat = null,
	object? source = null,
	TProperty? fallbackValue = null,
	TProperty? targetNullValue = null) where TSource : BindableObject
    {
        throw new InvalidOperationException($"The method call to {nameof(SetBinding<TSource, TProperty>)} was not intercepted.");
    }
}

Also, would it be useful to think about introducing a generic IValueConverter<TFrom, TTo> or even IValueConverter<TFrom, TTo, TParameter>? I know that converters are often used to convert from multiple value types but if there is a use case that only needs to convert from one type then this allows more types to flow through the linker's analysis and hopefully not trim out the types. I don't think that following the outdated Interface of the WPF days is useful here.

Finally, keep up the good work 💪

[simonrozsival]

This new API has been released and is part of .NET MAUI 9 RC 1.