Allow markup in selection prompts

Closes #221

src/Spectre.Console.Tests/Unit/MarkupTests.cs

@@ -25,6 +25,22 @@ namespace Spectre.Console.Tests.Unit
             }
         }
 
+        public sealed class TheRemoveMethod
+        {
+            [Theory]
+            [InlineData("Hello World", "Hello World")]
+            [InlineData("Hello [blue]World", "Hello World")]
+            [InlineData("Hello [blue]World[/]", "Hello World")]
+            public void Should_Remove_Markup_From_Text(string input, string expected)
+            {
+                // Given, When
+                var result = Markup.Remove(input);
+
+                // Then
+                result.ShouldBe(expected);
+            }
+        }
+
         [Theory]
         [InlineData("Hello [[ World ]")]
         [InlineData("Hello [[ World ] !")]

src/Spectre.Console/Extensions/StringExtensions.cs

@@ -34,6 +34,32 @@ namespace Spectre.Console
                 .ReplaceExact("]", "]]");
         }
 
+        /// <summary>
+        /// Removes markup from the specified string.
+        /// </summary>
+        /// <param name="text">The text to remove markup from.</param>
+        /// <returns>A string that does not have any markup.</returns>
+        public static string RemoveMarkup(this string? text)
+        {
+            if (string.IsNullOrWhiteSpace(text))
+            {
+                return string.Empty;
+            }
+
+            var result = new StringBuilder();
+
+            var tokenizer = new MarkupTokenizer(text);
+            while (tokenizer.MoveNext() && tokenizer.Current != null)
+            {
+                if (tokenizer.Current.Kind == MarkupTokenKind.Text)
+                {
+                    result.Append(tokenizer.Current.Value);
+                }
+            }
+
+            return result.ToString();
+        }
+
         internal static int CellLength(this string text, RenderContext context)
         {
             if (context is null)

src/Spectre.Console/Widgets/Markup.cs

@@ -63,5 +63,20 @@ namespace Spectre.Console
 
             return text.EscapeMarkup();
         }
+
+        /// <summary>
+        /// Removes markup from the specified string.
+        /// </summary>
+        /// <param name="text">The text to remove markup from.</param>
+        /// <returns>A string that does not have any markup.</returns>
+        public static string Remove(string text)
+        {
+            if (text is null)
+            {
+                throw new ArgumentNullException(nameof(text));
+            }
+
+            return text.RemoveMarkup();
+        }
     }
 }

src/Spectre.Console/Widgets/Prompt/Rendering/RenderableMultiSelectionList.cs

@@ -81,10 +81,11 @@ namespace Spectre.Console
                 var checkbox = selected ? SelectedCheckbox : Checkbox;
 
                 var style = current ? _highlightStyle : Style.Plain;
+                var item = current
+                    ? new Text(choice.Item.RemoveMarkup(), style)
+                    : (IRenderable)new Markup(choice.Item, style);
 
-                grid.AddRow(
-                    new Markup($"{prompt}{checkbox}", style),
-                    new Markup(choice.Item.EscapeMarkup(), style));
+                grid.AddRow(new Markup(prompt + checkbox, style), item);
             }
 
             list.Add(grid);

src/Spectre.Console/Widgets/Prompt/Rendering/RenderableSelectionList.cs

@@ -56,9 +56,11 @@ namespace Spectre.Console
                 var prompt = choice.Index == pointerIndex ? Prompt : string.Empty;
                 var style = current ? _highlightStyle : Style.Plain;
 
-                grid.AddRow(
-                    new Markup(prompt, style),
-                    new Markup(choice.Item.EscapeMarkup(), style));
+                var item = current
+                    ? new Text(choice.Item.RemoveMarkup(), style)
+                    : (IRenderable)new Markup(choice.Item, style);
+
+                grid.AddRow(new Markup(prompt, style), item);
             }
 
             list.Add(grid);