From c70a8b8fc55bfa388773f923e648a9f7e51287b6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Luthi?= <cedric.luthi@gmail.com>
Date: Tue, 10 Sep 2024 14:01:32 +0200
Subject: [PATCH] Improve exception if a (multi)selection prompt is used
 incorrectly

Before this commit, the selection prompt would throw an `InvalidOperationException` (Sequence contains no elements) and the multi selection prompt would throw an `ArgumentOutOfRangeException` (Index was out of range. Must be non-negative and less than the size of the collection.)

Both would occur because the prompts were never meant to be empty.
---
 src/Spectre.Console/Prompts/List/ListPrompt.cs  |  5 +++++
 .../Unit/Prompts/MultiSelectionPromptTests.cs   | 17 +++++++++++++++++
 .../Unit/Prompts/SelectionPromptTests.cs        | 16 ++++++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/src/Spectre.Console/Prompts/List/ListPrompt.cs b/src/Spectre.Console/Prompts/List/ListPrompt.cs
index c668502..ca0fa3f 100644
--- a/src/Spectre.Console/Prompts/List/ListPrompt.cs
+++ b/src/Spectre.Console/Prompts/List/ListPrompt.cs
@@ -42,6 +42,11 @@ internal sealed class ListPrompt<T>
         }
 
         var nodes = tree.Traverse().ToList();
+        if (nodes.Count == 0)
+        {
+            throw new InvalidOperationException("Cannot show an empty selection prompt. Please call the AddChoice() method to configure the prompt.");
+        }
+
         var state = new ListPromptState<T>(nodes, converter, _strategy.CalculatePageSize(_console, nodes.Count, requestedPageSize), wrapAround, selectionMode, skipUnselectableItems, searchEnabled);
         var hook = new ListPromptRenderHook<T>(_console, () => BuildRenderable(state));
 
diff --git a/src/Tests/Spectre.Console.Tests/Unit/Prompts/MultiSelectionPromptTests.cs b/src/Tests/Spectre.Console.Tests/Unit/Prompts/MultiSelectionPromptTests.cs
index 405e154..43b1d5c 100644
--- a/src/Tests/Spectre.Console.Tests/Unit/Prompts/MultiSelectionPromptTests.cs
+++ b/src/Tests/Spectre.Console.Tests/Unit/Prompts/MultiSelectionPromptTests.cs
@@ -127,6 +127,23 @@ public sealed class MultiSelectionPromptTests
         // Then
         action.ShouldThrow<ArgumentOutOfRangeException>();
     }
+
+    [Fact] public void Should_Throw_Meaningful_Exception_For_Empty_Prompt()
+    {
+        // Given
+        var console = new TestConsole();
+        console.Profile.Capabilities.Interactive = true;
+        console.Input.PushKey(ConsoleKey.Spacebar);
+
+        var prompt = new MultiSelectionPrompt<string>();
+
+        // When
+        Action action = () => prompt.Show(console);
+
+        // Then
+        var exception = action.ShouldThrow<InvalidOperationException>();
+        exception.Message.ShouldBe("Cannot show an empty selection prompt. Please call the AddChoice() method to configure the prompt.");
+    }
 }
 
 file sealed class CustomItem
diff --git a/src/Tests/Spectre.Console.Tests/Unit/Prompts/SelectionPromptTests.cs b/src/Tests/Spectre.Console.Tests/Unit/Prompts/SelectionPromptTests.cs
index 9d3e7ac..2e066c5 100644
--- a/src/Tests/Spectre.Console.Tests/Unit/Prompts/SelectionPromptTests.cs
+++ b/src/Tests/Spectre.Console.Tests/Unit/Prompts/SelectionPromptTests.cs
@@ -114,6 +114,22 @@ public sealed class SelectionPromptTests
         // Then
         selection.ShouldBe(choices[1]);
     }
+
+    [Fact] public void Should_Throw_Meaningful_Exception_For_Empty_Prompt()
+    {
+        // Given
+        var console = new TestConsole();
+        console.Profile.Capabilities.Interactive = true;
+
+        var prompt = new SelectionPrompt<string>();
+
+        // When
+        Action action = () => prompt.Show(console);
+
+        // Then
+        var exception = action.ShouldThrow<InvalidOperationException>();
+        exception.Message.ShouldBe("Cannot show an empty selection prompt. Please call the AddChoice() method to configure the prompt.");
+    }
 }
 
 file sealed class CustomSelectionItem