Add support for selecting prompt items

Closes #447

src/Spectre.Console/Extensions/StackExtensions.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+
+namespace Spectre.Console
+{
+    internal static class StackExtensions
+    {
+        public static void PushRange<T>(this Stack<T> stack, IEnumerable<T> source)
+        {
+            if (stack is null)
+            {
+                throw new ArgumentNullException(nameof(stack));
+            }
+
+            if (source != null)
+            {
+                foreach (var item in source)
+                {
+                    stack.Push(item);
+                }
+            }
+        }
+    }
+}

src/Spectre.Console/Widgets/Prompt/IMultiSelectionItem.cs

@@ -7,6 +7,11 @@ namespace Spectre.Console
     public interface IMultiSelectionItem<T> : ISelectionItem<T>
         where T : notnull
     {
+        /// <summary>
+        /// Gets a value indicating whether or not this item is selected.
+        /// </summary>
+        bool IsSelected { get; }
+
         /// <summary>
         /// Selects the item.
         /// </summary>

src/Spectre.Console/Widgets/Prompt/List/ListPromptItem.cs

@@ -9,7 +9,7 @@ namespace Spectre.Console
         public ListPromptItem<T>? Parent { get; }
         public List<ListPromptItem<T>> Children { get; }
         public int Depth { get; }
-        public bool Selected { get; set; }
+        public bool IsSelected { get; set; }
 
         public bool IsGroup => Children.Count > 0;
 
@@ -23,7 +23,7 @@ namespace Spectre.Console
 
         public IMultiSelectionItem<T> Select()
         {
-            Selected = true;
+            IsSelected = true;
             return this;
         }
 

src/Spectre.Console/Widgets/Prompt/List/ListPromptTree.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 
 namespace Spectre.Console
@@ -6,10 +7,29 @@ namespace Spectre.Console
         where T : notnull
     {
         private readonly List<ListPromptItem<T>> _roots;
+        private readonly IEqualityComparer<T> _comparer;
 
-        public ListPromptTree()
+        public ListPromptTree(IEqualityComparer<T> comparer)
         {
             _roots = new List<ListPromptItem<T>>();
+            _comparer = comparer ?? throw new ArgumentNullException(nameof(comparer));
+        }
+
+        public ListPromptItem<T>? Find(T item)
+        {
+            var stack = new Stack<ListPromptItem<T>>(_roots);
+            while (stack.Count > 0)
+            {
+                var current = stack.Pop();
+                if (_comparer.Equals(item, current.Data))
+                {
+                    return current;
+                }
+
+                stack.PushRange(current.Children);
+            }
+
+            return null;
         }
 
         public void Add(ListPromptItem<T> node)

src/Spectre.Console/Widgets/Prompt/MultiSelectionPrompt.cs

@@ -13,8 +13,6 @@ namespace Spectre.Console
     public sealed class MultiSelectionPrompt<T> : IPrompt<List<T>>, IListPromptStrategy<T>
         where T : notnull
     {
-        private readonly ListPromptTree<T> _tree;
-
         /// <summary>
         /// Gets or sets the title.
         /// </summary>
@@ -59,12 +57,18 @@ namespace Spectre.Console
         /// </summary>
         public SelectionMode Mode { get; set; } = SelectionMode.Leaf;
 
+        internal ListPromptTree<T> Tree { get; }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="MultiSelectionPrompt{T}"/> class.
         /// </summary>
-        public MultiSelectionPrompt()
+        /// <param name="comparer">
+        /// The <see cref="IEqualityComparer{T}"/> implementation to use when comparing items,
+        /// or <c>null</c> to use the default <see cref="IEqualityComparer{T}"/> for the type of the item.
+        /// </param>
+        public MultiSelectionPrompt(IEqualityComparer<T>? comparer = null)
         {
-            _tree = new ListPromptTree<T>();
+            Tree = new ListPromptTree<T>(comparer ?? EqualityComparer<T>.Default);
         }
 
         /// <summary>
@@ -75,7 +79,7 @@ namespace Spectre.Console
         public IMultiSelectionItem<T> AddChoice(T item)
         {
             var node = new ListPromptItem<T>(item);
-            _tree.Add(node);
+            Tree.Add(node);
             return node;
         }
 
@@ -84,18 +88,18 @@ namespace Spectre.Console
         {
             // Create the list prompt
             var prompt = new ListPrompt<T>(console, this);
-            var result = prompt.Show(_tree, PageSize);
+            var result = prompt.Show(Tree, PageSize);
 
             if (Mode == SelectionMode.Leaf)
             {
                 return result.Items
-                    .Where(x => x.Selected && x.Children.Count == 0)
+                    .Where(x => x.IsSelected && x.Children.Count == 0)
                     .Select(x => x.Data)
                     .ToList();
             }
 
             return result.Items
-                .Where(x => x.Selected)
+                .Where(x => x.IsSelected)
                 .Select(x => x.Data)
                 .ToList();
         }
@@ -105,7 +109,7 @@ namespace Spectre.Console
         {
             if (key.Key == ConsoleKey.Enter)
             {
-                if (Required && state.Items.None(x => x.Selected))
+                if (Required && state.Items.None(x => x.IsSelected))
                 {
                     // Selection not permitted
                     return ListPromptInputResult.None;
@@ -118,14 +122,14 @@ namespace Spectre.Console
             if (key.Key == ConsoleKey.Spacebar)
             {
                 var current = state.Items[state.Index];
-                var select = !current.Selected;
+                var select = !current.IsSelected;
 
                 if (Mode == SelectionMode.Leaf)
                 {
                     // Select the node and all it's children
                     foreach (var item in current.Traverse(includeSelf: true))
                     {
-                        item.Selected = select;
+                        item.IsSelected = select;
                     }
 
                     // Visit every parent and evaluate if it's selection
@@ -133,13 +137,13 @@ namespace Spectre.Console
                     var parent = current.Parent;
                     while (parent != null)
                     {
-                        parent.Selected = parent.Traverse(includeSelf: false).All(x => x.Selected);
+                        parent.IsSelected = parent.Traverse(includeSelf: false).All(x => x.IsSelected);
                         parent = parent.Parent;
                     }
                 }
                 else
                 {
-                    current.Selected = !current.Selected;
+                    current.IsSelected = !current.IsSelected;
                 }
 
                 // Refresh the list
@@ -209,7 +213,7 @@ namespace Spectre.Console
                     text = text.RemoveMarkup();
                 }
 
-                var checkbox = item.Node.Selected
+                var checkbox = item.Node.IsSelected
                     ? (item.Node.IsGroup && Mode == SelectionMode.Leaf
                         ? ListPromptConstants.GroupSelectedCheckbox : ListPromptConstants.SelectedCheckbox)
                     : ListPromptConstants.Checkbox;

src/Spectre.Console/Widgets/Prompt/MultiSelectionPromptExtensions.cs

@@ -130,40 +130,19 @@ namespace Spectre.Console
         /// </summary>
         /// <typeparam name="T">The prompt result type.</typeparam>
         /// <param name="obj">The prompt.</param>
-        /// <param name="index">The index of the item to select.</param>
+        /// <param name="item">The item to select.</param>
         /// <returns>The same instance so that multiple calls can be chained.</returns>
-        [Obsolete("Selection by index has been made obsolete", error: true)]
+        public static MultiSelectionPrompt<T> Select<T>(this MultiSelectionPrompt<T> obj, T item)
-        public static MultiSelectionPrompt<T> Select<T>(this MultiSelectionPrompt<T> obj, int index)
             where T : notnull
         {
-            return obj;
+            if (obj is null)
+            {
+                throw new ArgumentNullException(nameof(obj));
             }
 
-        /// <summary>
+            var node = obj.Tree.Find(item);
-        /// Marks multiple items as selected.
+            node?.Select();
-        /// </summary>
-        /// <typeparam name="T">The prompt result type.</typeparam>
-        /// <param name="obj">The prompt.</param>
-        /// <param name="indices">The indices of the items to select.</param>
-        /// <returns>The same instance so that multiple calls can be chained.</returns>
-        [Obsolete("Selection by index has been made obsolete", error: true)]
-        public static MultiSelectionPrompt<T> Select<T>(this MultiSelectionPrompt<T> obj, params int[] indices)
-            where T : notnull
-        {
-            return obj;
-        }
 
-        /// <summary>
-        /// Marks multiple items as selected.
-        /// </summary>
-        /// <typeparam name="T">The prompt result type.</typeparam>
-        /// <param name="obj">The prompt.</param>
-        /// <param name="indices">The indices of the items to select.</param>
-        /// <returns>The same instance so that multiple calls can be chained.</returns>
-        [Obsolete("Selection by index has been made obsolete", error: true)]
-        public static MultiSelectionPrompt<T> Select<T>(this MultiSelectionPrompt<T> obj, IEnumerable<int> indices)
-            where T : notnull
-        {
             return obj;
         }
 

src/Spectre.Console/Widgets/Prompt/SelectionPrompt.cs

@@ -57,7 +57,7 @@ namespace Spectre.Console
         /// </summary>
         public SelectionPrompt()
         {
-            _tree = new ListPromptTree<T>();
+            _tree = new ListPromptTree<T>(EqualityComparer<T>.Default);
         }
 
         /// <summary>

test/Spectre.Console.Tests/Unit/Prompt/MultiSelectionPromptTests.cs

@@ -0,0 +1,86 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using Shouldly;
+using Xunit;
+
+namespace Spectre.Console.Tests.Unit
+{
+    public sealed class MultiSelectionPromptTests
+    {
+        private class CustomItem
+        {
+            public int X { get; set; }
+            public int Y { get; set; }
+
+            public class Comparer : IEqualityComparer<CustomItem>
+            {
+                public bool Equals(CustomItem x, CustomItem y)
+                {
+                    return x.X == y.X && x.Y == y.Y;
+                }
+
+                public int GetHashCode([DisallowNull] CustomItem obj)
+                {
+                    throw new NotImplementedException();
+                }
+            }
+        }
+
+        [Fact]
+        public void Should_Not_Mark_Item_As_Selected_By_Default()
+        {
+            // Given
+            var prompt = new MultiSelectionPrompt<int>();
+
+            // When
+            var choice = prompt.AddChoice(32);
+
+            // Then
+            choice.IsSelected.ShouldBeFalse();
+        }
+
+        [Fact]
+        public void Should_Mark_Item_As_Selected()
+        {
+            // Given
+            var prompt = new MultiSelectionPrompt<int>();
+            var choice = prompt.AddChoice(32);
+
+            // When
+            prompt.Select(32);
+
+            // Then
+            choice.IsSelected.ShouldBeTrue();
+        }
+
+        [Fact]
+        public void Should_Mark_Custom_Item_As_Selected_If_The_Same_Reference_Is_Used()
+        {
+            // Given
+            var prompt = new MultiSelectionPrompt<CustomItem>();
+            var item = new CustomItem { X = 18, Y = 32 };
+            var choice = prompt.AddChoice(item);
+
+            // When
+            prompt.Select(item);
+
+            // Then
+            choice.IsSelected.ShouldBeTrue();
+        }
+
+        [Fact]
+        public void Should_Mark_Custom_Item_As_Selected_If_A_Comparer_Is_Provided()
+        {
+            // Given
+            var prompt = new MultiSelectionPrompt<CustomItem>(new CustomItem.Comparer());
+            var choice = prompt.AddChoice(new CustomItem { X = 18, Y = 32 });
+
+            // When
+            prompt.Select(new CustomItem { X = 18, Y = 32 });
+
+            // Then
+            choice.IsSelected.ShouldBeTrue();
+        }
+    }
+}