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RelativeSource Binding Bug Fixes (Gh8450) (#8541)
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* RelativeSource Binding Bug FIxes

(1) Fix RelativeSource-FindAncestorBindingContext bindings not re-applying on ancestor BindingContext or ancestry changes; 
(2) fix incorrect interpretation of AncestorLevel; 
(3) much more robust unit tests for RelativeSource ancestor-type binding (#4)

* Update Xamarin.Forms.Core.UnitTests/RelativeSourceBindingTests.cs

Co-Authored-By: Samantha Houts <samhouts@users.noreply.github.com>
Fixes #8450
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@legistek @samhouts
legistek authored and samhouts committed Nov 22, 2019
1 parent 1ce747e commit 16cdd28
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251 changes: 200 additions & 51 deletions Xamarin.Forms.Core.UnitTests/RelativeSourceBindingTests.cs
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Expand Up @@ -41,94 +41,243 @@ public void RelativeSourceSelfBinding()
[Test]
public void RelativeSourceAncestorTypeBinding()
{
string bindingContext0 = "bc0";
string bindingContext1 = "bc1";
string bindingContext2 = "bc2";
Grid grid = new Grid();

StackLayout stack0 = new StackLayout
{
StyleId = "stack0",
BindingContext = bindingContext0,
BackgroundColor = Color.Red
};

StackLayout stack1 = new StackLayout
{
StyleId = "stack1",
BackgroundColor = Color.Green
};

StackLayout stack2 = new StackLayout
{
StyleId = "stack2",
BindingContext = bindingContext2
BackgroundColor = Color.Blue
};

Label label0 = new Label
Label label0 = new Label();
Label label1 = new Label();
Label label2 = new Label();
var person0 = new PersonViewModel
{
StyleId = "label0",
Name = "Person 0",
};
Label label1 = new Label
var person1 = new PersonViewModel
{
StyleId = "label1",
Name = "Person 1",
};
Label label2 = new Label
var person2 = new PersonViewModel
{
StyleId = "label2",
Name = "Person 2",
};

stack0.Children.Add(stack1);
stack0.Children.Add(label2);
stack1.Children.Add(label0);
stack1.Children.Add(label1);
stack2.Children.Add(stack1);
stack1.Children.Add(stack0);
stack0.Children.Add(grid);

label0.SetBinding(Label.TextProperty, new Binding
{
Path = nameof(StackLayout.StyleId),
Path = nameof(PersonViewModel.Name),
Source = new RelativeBindingSource(RelativeBindingSourceMode.FindAncestorBindingContext, typeof(PersonViewModel), 1)
});
label0.SetBinding(Label.TextColorProperty, new Binding
{
Path = nameof(StackLayout.BackgroundColor),
Source = new RelativeBindingSource(
mode: RelativeBindingSourceMode.FindAncestor,
ancestorType: typeof(StackLayout))
RelativeBindingSourceMode.FindAncestor, typeof(StackLayout), 1)
});
Assert.IsNull(label0.Text);
Assert.AreEqual(Label.TextColorProperty.DefaultValue, label0.TextColor);

label1.SetBinding(Label.TextProperty, new Binding
{
Path = nameof(StackLayout.StyleId),
Source = new RelativeBindingSource(
mode: RelativeBindingSourceMode.FindAncestor,
ancestorType: typeof(StackLayout),
ancestorLevel: 2)
Path = nameof(PersonViewModel.Name),
Source = new RelativeBindingSource(RelativeBindingSourceMode.FindAncestorBindingContext, typeof(PersonViewModel), 2)
});
label1.SetBinding(Label.TextColorProperty, new Binding
{
Path = nameof(StackLayout.BackgroundColor),
Source = new RelativeBindingSource(RelativeBindingSourceMode.FindAncestor, typeof(StackLayout), 2)
});
Assert.IsNull(label1.Text);
Assert.AreEqual(Label.TextColorProperty.DefaultValue, label1.TextColor);

label2.SetBinding(Label.TextProperty, new Binding
{
Path = nameof(StackLayout.StyleId),
Source = new RelativeBindingSource(
mode: RelativeBindingSourceMode.FindAncestor,
ancestorType: typeof(StackLayout),
ancestorLevel: 10)
Path = nameof(PersonViewModel.Name),
Source = new RelativeBindingSource(RelativeBindingSourceMode.FindAncestorBindingContext, typeof(PersonViewModel), 3)
});
label2.SetBinding(Label.TextColorProperty, new Binding
{
Path = nameof(StackLayout.BackgroundColor),
Source = new RelativeBindingSource(RelativeBindingSourceMode.FindAncestor, typeof(StackLayout), 3)
});
Assert.IsNull(label2.Text);
Assert.AreEqual(Label.TextColorProperty.DefaultValue, label2.TextColor);

grid.Children.Add(label0);
grid.Children.Add(label1);
grid.Children.Add(label2);

//// BindingContext changes

Assert.AreEqual(label0.Text, stack1.StyleId);
Assert.AreEqual(label1.Text, stack0.StyleId);
// stack2
// stack1
// stack0
// grid
// label0 (min level 1) = stack0/null
// label1 (min level 2) = stack1/null
// label2 (min level 3) = stack2/null
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, stack1.BackgroundColor);
Assert.AreEqual(label2.TextColor, stack2.BackgroundColor);
Assert.IsNull(label0.Text);
Assert.IsNull(label1.Text);
Assert.IsNull(label2.Text);

// stack2 (person2)
// stack1 (person2*)
// stack0 (person2*)
// grid (person2*)
// label0 (min level 1) = stack0/person2
// label1 (min level 2) = stack1/null
// label2 (min level 3) = stack2/null
stack2.BindingContext = person2;
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, stack1.BackgroundColor);
Assert.AreEqual(label2.TextColor, stack2.BackgroundColor);
Assert.AreEqual(label0.Text, person2.Name);
Assert.IsNull(label1.Text);
Assert.IsNull(label2.Text);

// Ensures RelativeBindingSource.AncestorType
// works correctly after immediate ancestor changed.
stack1.Children.Remove(label0);
// stack2 (person2)
// stack1 (person1)
// stack0 (person1*)
// grid (person1*)
// label0 (min level 1) = stack0/person1
// label1 (min level 2) = stack1/person2
// label2 (min level 3) = stack2/null
stack1.BindingContext = person1;
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, stack1.BackgroundColor);
Assert.AreEqual(label2.TextColor, stack2.BackgroundColor);
Assert.AreEqual(label0.Text, person1.Name);
Assert.AreEqual(label1.Text, person2.Name);
Assert.AreEqual(Label.TextProperty.DefaultValue, label2.Text);

// stack2 (person2)
// stack1 (person1)
// stack0 (person0)
// grid (person0*)
// label0 (min level 1) = stack0/person0
// label1 (min level 2) = stack1/person1
// label2 (min level 3) = stack2/person2
stack0.BindingContext = person0;
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, stack1.BackgroundColor);
Assert.AreEqual(label2.TextColor, stack2.BackgroundColor);
Assert.AreEqual(label0.Text, person0.Name);
Assert.AreEqual(label1.Text, person1.Name);
Assert.AreEqual(label2.Text, person2.Name);

// stack2
// stack1 (person1)
// stack0 (person0)
// grid (person0*)
// label0 (min level 1) = stack0/person0
// label1 (min level 2) = stack1/person1
// label2 (min level 3) = stack2/null
stack2.BindingContext = null;
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, stack1.BackgroundColor);
Assert.AreEqual(label2.TextColor, stack2.BackgroundColor);
Assert.AreEqual(label0.Text, person0.Name);
Assert.AreEqual(label1.Text, person1.Name);
Assert.IsNull(label2.Text);

// stack2
// stack1
// stack0 (person0)
// grid (person0*)
// label0 (min level 1) = stack0/person0
// label1 (min level 2) = stack1/null
// label2 (min level 3) = stack2/null
stack1.BindingContext = null;
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, stack1.BackgroundColor);
Assert.AreEqual(label2.TextColor, stack2.BackgroundColor);
Assert.AreEqual(label0.Text, person0.Name);
Assert.IsNull(label1.Text);
Assert.IsNull(label2.Text);

// stack2
// stack1
// stack0
// label0 (min level 1) = stack0/null
// label1 (min level 2) = stack1/null
// label2 (min level 3) = stack2/null
stack0.BindingContext = null;
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, stack1.BackgroundColor);
Assert.AreEqual(label2.TextColor, stack2.BackgroundColor);
Assert.IsNull(label0.Text);

stack0.Children.Add(label0);
Assert.IsNull(label1.Text);
Assert.IsNull(label2.Text);

stack0.BindingContext = person0;
stack1.BindingContext = person1;
stack2.BindingContext = person2;

Assert.AreEqual(label0.Text, stack0.StyleId);
Assert.AreEqual(label0.BindingContext, stack0.BindingContext);
//// Parent Changes

// And after distant ancestor changed
stack0.Children.Remove(stack1);
stack2.Children.Add(stack1);
// stack2 (person2)
// stack1 (person1)
// stack0 (person0)
// label0 (min level 1) = stack0/person0
// label1 (min level 2) = stack1/person1
// label2 (min level 3) = null/null
stack2.Children.Clear();
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, stack1.BackgroundColor);
Assert.AreEqual(label2.TextColor, StackLayout.BackgroundColorProperty.DefaultValue);
Assert.AreEqual(label0.Text, person0.Name);
Assert.AreEqual(label1.Text, person1.Name);
Assert.IsNull(label2.Text);

// stack2 (person2)
// stack1 (person1)
// stack0 (person0)
// label0 (min level 1) = stack0/person0
// label1 (min level 2) = null/null
// label2 (min level 3) = null/null
stack1.Children.Clear();
Assert.AreEqual(label0.TextColor, stack0.BackgroundColor);
Assert.AreEqual(label1.TextColor, StackLayout.BackgroundColorProperty.DefaultValue);
Assert.AreEqual(label2.TextColor, StackLayout.BackgroundColorProperty.DefaultValue);
Assert.AreEqual(label0.Text, person0.Name);
Assert.IsNull(label1.Text);
Assert.IsNull(label2.Text);

Assert.AreEqual(label1.Text, stack2.StyleId);
Assert.AreEqual(label1.BindingContext, stack2.BindingContext);
// stack2 (person2)
// stack1 (person1)
// stack0 (person0)
// grid
// label0 (min level 1) = null/null
// label1 (min level 2) = null/null
// label2 (min level 3) = null/null
stack0.Children.Clear();
Assert.AreEqual(label0.TextColor, StackLayout.BackgroundColorProperty.DefaultValue);
Assert.AreEqual(label1.TextColor, StackLayout.BackgroundColorProperty.DefaultValue);
Assert.AreEqual(label2.TextColor, StackLayout.BackgroundColorProperty.DefaultValue);
Assert.IsNull(label0.Text);
Assert.IsNull(label1.Text);
Assert.IsNull(label2.Text);
}

// And after parent binding context changed
stack2.BindingContext = "foobar";
Assert.AreEqual(label1.Text, stack2.StyleId);
Assert.AreEqual(label1.BindingContext, "foobar");
class PersonViewModel
{
public string Name { get; set; }
}
}

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