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Support nullable stream binding operator (?^) #22069

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78 changes: 71 additions & 7 deletions src/Avalonia.Base/Data/CompiledBindingPath.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,7 @@ internal void BuildExpression(List<ExpressionNode> result, out bool isRooted)
isRooted = true;
break;
case IStronglyTypedStreamElement stream:
node = new StreamNode(stream.CreatePlugin());
node = new StreamNode(stream.CreatePlugin(), stream.AcceptsNull);
break;
case ITypeCastElement typeCast:
node = new FuncTransformNode(typeCast.Cast);
Expand Down Expand Up @@ -152,7 +152,13 @@ public CompiledBindingPathBuilder Command(string methodName, Action<object, obje

public CompiledBindingPathBuilder StreamTask<T>()
{
_elements.Add(new TaskStreamPathElement<T>());
_elements.Add(new TaskStreamPathElement<T>(acceptsNull: false));
return this;
}

public CompiledBindingPathBuilder StreamTask<T>(bool acceptsNull)
{
_elements.Add(new TaskStreamPathElement<T>(acceptsNull));
return this;
}

Expand All @@ -163,9 +169,22 @@ public CompiledBindingPathBuilder StreamTask()
return this;
}

[RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
public CompiledBindingPathBuilder StreamTask(bool acceptsNull)
{
_elements.Add(new TaskStreamPathElement(acceptsNull));
return this;
}

public CompiledBindingPathBuilder StreamObservable<T>()
{
_elements.Add(new ObservableStreamPathElement<T>());
_elements.Add(new ObservableStreamPathElement<T>(acceptsNull: false));
return this;
}

public CompiledBindingPathBuilder StreamObservable<T>(bool acceptsNull)
{
_elements.Add(new ObservableStreamPathElement<T>(acceptsNull));
return this;
}

Expand All @@ -176,6 +195,13 @@ public CompiledBindingPathBuilder StreamObservable()
return this;
}

[RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
public CompiledBindingPathBuilder StreamObservable(bool acceptsNull)
{
_elements.Add(new ObservableStreamPathElement(acceptsNull));
return this;
}

public CompiledBindingPathBuilder Self()
{
_elements.Add(new SelfPathElement());
Expand Down Expand Up @@ -303,6 +329,8 @@ public MethodAsCommandElement(string methodName, Action<object, object?> execute

internal interface IStronglyTypedStreamElement : ICompiledBindingPathElement
{
bool AcceptsNull { get; }

IStreamPlugin CreatePlugin();
}

Expand All @@ -315,30 +343,66 @@ internal interface ITypeCastElement : ICompiledBindingPathElement

internal class TaskStreamPathElement<T> : IStronglyTypedStreamElement
{
public static readonly TaskStreamPathElement<T> Instance = new TaskStreamPathElement<T>();
public static readonly TaskStreamPathElement<T> Instance = new TaskStreamPathElement<T>(acceptsNull: false);

public TaskStreamPathElement(bool acceptsNull)
{
AcceptsNull = acceptsNull;
}

public bool AcceptsNull { get; }

public IStreamPlugin CreatePlugin() => new TaskStreamPlugin<T>();
}

[RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
internal class TaskStreamPathElement : IStronglyTypedStreamElement
{
public static readonly TaskStreamPathElement Instance = new TaskStreamPathElement();
public static readonly TaskStreamPathElement Instance = new TaskStreamPathElement(acceptsNull: false);

public TaskStreamPathElement() : this(acceptsNull: false)
{
}

public TaskStreamPathElement(bool acceptsNull)
{
AcceptsNull = acceptsNull;
}

public bool AcceptsNull { get; }

public IStreamPlugin CreatePlugin() => new TaskStreamPlugin();
}

internal class ObservableStreamPathElement<T> : IStronglyTypedStreamElement
{
public static readonly ObservableStreamPathElement<T> Instance = new ObservableStreamPathElement<T>();
public static readonly ObservableStreamPathElement<T> Instance = new ObservableStreamPathElement<T>(acceptsNull: false);

public ObservableStreamPathElement(bool acceptsNull)
{
AcceptsNull = acceptsNull;
}

public bool AcceptsNull { get; }

public IStreamPlugin CreatePlugin() => new ObservableStreamPlugin<T>();
}

[RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
internal class ObservableStreamPathElement : IStronglyTypedStreamElement
{
public static readonly ObservableStreamPathElement Instance = new ObservableStreamPathElement();
public static readonly ObservableStreamPathElement Instance = new ObservableStreamPathElement(acceptsNull: false);

public ObservableStreamPathElement() : this(acceptsNull: false)
{
}

public ObservableStreamPathElement(bool acceptsNull)
{
AcceptsNull = acceptsNull;
}

public bool AcceptsNull { get; }

public IStreamPlugin CreatePlugin() => new ObservableStreamPlugin();
}
Expand Down
14 changes: 13 additions & 1 deletion src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginStreamNode.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,17 +10,29 @@ namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
[RequiresDynamicCode(TrimmingMessages.ExpressionNodeRequiresDynamicCodeMessage)]
internal sealed class DynamicPluginStreamNode : ExpressionNode
{
private readonly bool _acceptsNull;
private IDisposable? _subscription;

public DynamicPluginStreamNode(bool acceptsNull)
{
_acceptsNull = acceptsNull;
}

override public void BuildString(StringBuilder builder)
{
builder.Append('^');
}

protected override void OnSourceChanged(object? source, Exception? dataValidationError)
{
if (!ValidateNonNullSource(source))
if (source is null)
{
if (_acceptsNull)
SetValue(null);
else
ValidateNonNullSource(source);
return;
}

var reference = new WeakReference<object?>(source);

Expand Down
12 changes: 10 additions & 2 deletions src/Avalonia.Base/Data/Core/ExpressionNodes/StreamNode.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,12 +6,14 @@ namespace Avalonia.Data.Core.ExpressionNodes;

internal sealed class StreamNode : ExpressionNode, IObserver<object?>
{
private readonly bool _acceptsNull;
private IStreamPlugin _plugin;
private IDisposable? _subscription;

public StreamNode(IStreamPlugin plugin)
public StreamNode(IStreamPlugin plugin, bool acceptsNull)
{
_plugin = plugin;
_acceptsNull = acceptsNull;
}

public override void BuildString(StringBuilder builder)
Expand All @@ -25,8 +27,14 @@ public override void BuildString(StringBuilder builder)

protected override void OnSourceChanged(object? source, Exception? dataValidationError)
{
if (!ValidateNonNullSource(source))
if (source is null)
{
if (_acceptsNull)
SetValue(null);
else
ValidateNonNullSource(source);
return;
}

if (_plugin.Start(new(source)) is { } accessor)
{
Expand Down
34 changes: 27 additions & 7 deletions src/Avalonia.Base/Data/Core/Parsers/BindingExpressionGrammar.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -140,10 +140,10 @@ private static State ParseStart(ref CharacterReader r, IList<INode> nodes)
nodes.Add(new EmptyExpressionNode());
return State.AfterMember;
}
else if (ParseStreamOperator(ref r))
else if (ParseStreamOperator(ref r, out var acceptsNull))
{
nodes.Add(new EmptyExpressionNode());
nodes.Add(new StreamNode());
nodes.Add(new StreamNode { AcceptsNull = acceptsNull });
return State.AfterMember;
}
else
Expand All @@ -166,9 +166,9 @@ private static State ParseAfterMember(ref CharacterReader r, IList<INode> nodes)
{
return acceptsNull ? State.BeforeMemberNullable : State.BeforeMember;
}
else if (ParseStreamOperator(ref r))
else if (ParseStreamOperator(ref r, out acceptsNull))
{
nodes.Add(new StreamNode());
nodes.Add(new StreamNode { AcceptsNull = acceptsNull });
return State.AfterMember;
}
else if (PeekOpenBracket(ref r))
Expand Down Expand Up @@ -441,9 +441,26 @@ private static bool PeekOpenBrace(ref CharacterReader r)
return !r.End && r.Peek == '(';
}

private static bool ParseStreamOperator(ref CharacterReader r)
private static bool ParseStreamOperator(ref CharacterReader r, out bool acceptsNull)
{
return !r.End && r.TakeIf('^');
acceptsNull = false;

if (r.End)
return false;

if (r.Peek == '^')
{
r.Take();
return true;
}

if (r.TakeIf("?^"))
{
acceptsNull = true;
return true;
}

return false;
}

private static bool ParseDollarSign(ref CharacterReader r)
Expand Down Expand Up @@ -521,7 +538,10 @@ public class IndexerNode : INode

public class NotNode : INode, ITransformNode { }

public class StreamNode : INode { }
public class StreamNode : INode
{
public bool AcceptsNull { get; set; }
}

public class SelfNode : INode { }

Expand Down
4 changes: 2 additions & 2 deletions src/Avalonia.Base/Data/Core/Parsers/ExpressionNodeFactory.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -59,8 +59,8 @@ internal static class ExpressionNodeFactory
node = null;
isRooted = true;
break;
case BindingExpressionGrammar.StreamNode:
node = new DynamicPluginStreamNode();
case BindingExpressionGrammar.StreamNode stream:
node = new DynamicPluginStreamNode(stream.AcceptsNull);
break;
case BindingExpressionGrammar.TypeCastNode typeCast:
node = new ReflectionTypeCastNode(LookupType(typeResolver, typeCast.Namespace, typeCast.TypeName));
Expand Down
40 changes: 33 additions & 7 deletions src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -152,7 +152,7 @@ private static XamlIlBindingPathNode TransformBindingPath(AstTransformationConte
case BindingExpressionGrammar.NotNode _:
transformNodes.Add(new XamlIlNotPathElementNode(context.Configuration.WellKnownTypes.Boolean));
break;
case BindingExpressionGrammar.StreamNode _:
case BindingExpressionGrammar.StreamNode streamNode:
{
IXamlType targetType = targetTypeResolver();
IXamlType? observableType;
Expand All @@ -168,7 +168,7 @@ private static XamlIlBindingPathNode TransformBindingPath(AstTransformationConte

if (observableType != null)
{
nodes.Add(new XamlIlStreamObservablePathElementNode(observableType.GenericArguments[0]));
nodes.Add(new XamlIlStreamObservablePathElementNode(observableType.GenericArguments[0], streamNode.AcceptsNull));
break;
}

Expand All @@ -180,7 +180,7 @@ private static XamlIlBindingPathNode TransformBindingPath(AstTransformationConte
if (currentType.GenericTypeDefinition?.Equals(taskType) == true)
{
foundTask = true;
nodes.Add(new XamlIlStreamTaskPathElementNode(currentType.GenericArguments[0]));
nodes.Add(new XamlIlStreamTaskPathElementNode(currentType.GenericArguments[0], streamNode.AcceptsNull));
break;
}
}
Expand Down Expand Up @@ -620,31 +620,57 @@ public void Emit(XamlIlEmitContext context, IXamlILEmitter codeGen)

class XamlIlStreamObservablePathElementNode : IXamlIlBindingPathElementNode
{
public XamlIlStreamObservablePathElementNode(IXamlType type)
private readonly bool _acceptsNull;

public XamlIlStreamObservablePathElementNode(IXamlType type, bool acceptsNull)
{
Type = type;
_acceptsNull = acceptsNull;
}

public IXamlType Type { get; }

public void Emit(XamlIlEmitContext context, IXamlILEmitter codeGen)
{
codeGen.EmitCall(context.GetAvaloniaTypes().CompiledBindingPathBuilder.GetMethod(m => m is { Name: "StreamObservable", IsGenericMethod: true }).MakeGenericMethod(new[] { Type }));
var parameterCount = 0;

if (_acceptsNull)
{
parameterCount = 1;
codeGen.Ldc_I4(1);
}

codeGen.EmitCall(context.GetAvaloniaTypes().CompiledBindingPathBuilder.GetMethod(m =>
m is { Name: "StreamObservable", IsGenericMethod: true } &&
m.Parameters.Count == parameterCount).MakeGenericMethod(new[] { Type }));
}
}

class XamlIlStreamTaskPathElementNode : IXamlIlBindingPathElementNode
{
public XamlIlStreamTaskPathElementNode(IXamlType type)
private readonly bool _acceptsNull;

public XamlIlStreamTaskPathElementNode(IXamlType type, bool acceptsNull)
{
Type = type;
_acceptsNull = acceptsNull;
}

public IXamlType Type { get; }

public void Emit(XamlIlEmitContext context, IXamlILEmitter codeGen)
{
codeGen.EmitCall(context.GetAvaloniaTypes().CompiledBindingPathBuilder.GetMethod(m => m is { Name: "StreamTask", IsGenericMethod: true }).MakeGenericMethod(new[] { Type }));
var parameterCount = 0;

if (_acceptsNull)
{
parameterCount = 1;
codeGen.Ldc_I4(1);
}

codeGen.EmitCall(context.GetAvaloniaTypes().CompiledBindingPathBuilder.GetMethod(m =>
m is { Name: "StreamTask", IsGenericMethod: true } &&
m.Parameters.Count == parameterCount).MakeGenericMethod(new[] { Type }));
}
}

Expand Down
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