From 75a23006bc62184aa108bbfad28a7e2e10c67ef5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Luthi?= <cedric.luthi@gmail.com>
Date: Wed, 6 May 2026 16:32:46 +0200
Subject: [PATCH 1/2] Add test for pair deconstruction with default values

Currently crashes with System.ArgumentNullException: Value cannot be null. (Parameter 'value')
---
 .../CommandAppTests.Pairs.cs                  | 32 +++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/src/Spectre.Console.Cli.Tests/CommandAppTests.Pairs.cs b/src/Spectre.Console.Cli.Tests/CommandAppTests.Pairs.cs
index 38d58ba..a9e2435 100644
--- a/src/Spectre.Console.Cli.Tests/CommandAppTests.Pairs.cs
+++ b/src/Spectre.Console.Cli.Tests/CommandAppTests.Pairs.cs
@@ -52,6 +52,13 @@ public sealed class ReadOnlyDictionarySettings : CommandSettings
             public IReadOnlyDictionary<string, string>? Values { get; set; }
         }
 
+        public sealed class DefaultValuesSettings : CommandSettings
+        {
+            [CommandOption("--var <VALUE>")]
+            [DefaultValue(new[] { "Monday=1", "Tuesday=2" })]
+            public IReadOnlyDictionary<DayOfWeek, int>? Values { get; set; }
+        }
+
         public sealed class StringIntDeconstructor : PairDeconstructor<string, string>
         {
             protected override (string Key, string Value) Deconstruct(string? value)
@@ -312,5 +319,30 @@ public void Should_Map_ReadOnly_Dictionary_Values()
                 pair.Values["baz"].ShouldBe("qux");
             });
         }
+
+        [Fact]
+        public void Should_Map_Default_Values()
+        {
+            // Given
+            var app = new CommandAppTester();
+            app.SetDefaultCommand<GenericCommand<DefaultValuesSettings>>();
+            app.Configure(config =>
+            {
+                config.PropagateExceptions();
+            });
+
+            // When
+            var result = app.Run();
+
+            // Then
+            result.ExitCode.ShouldBe(0);
+            result.Settings.ShouldBeOfType<DefaultValuesSettings>().And(pair =>
+            {
+                pair.Values.ShouldNotBeNull();
+                pair.Values.Count.ShouldBe(2);
+                pair.Values[DayOfWeek.Monday].ShouldBe(1);
+                pair.Values[DayOfWeek.Tuesday].ShouldBe(2);
+            });
+        }
     }
 }
\ No newline at end of file

From acdd222dec8d13456c36de4cf4b465a0fa238194 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Luthi?= <cedric.luthi@gmail.com>
Date: Wed, 6 May 2026 16:35:37 +0200
Subject: [PATCH 2/2] Fix pair deconstruction with default values

Fixes #75
---
 .../Internal/Binding/CommandValueBinder.cs               | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/Spectre.Console.Cli/Internal/Binding/CommandValueBinder.cs b/src/Spectre.Console.Cli/Internal/Binding/CommandValueBinder.cs
index 8dfbee4..0c9541d 100644
--- a/src/Spectre.Console.Cli/Internal/Binding/CommandValueBinder.cs
+++ b/src/Spectre.Console.Cli/Internal/Binding/CommandValueBinder.cs
@@ -54,10 +54,13 @@ private object GetLookup(CommandParameter parameter, ITypeResolver resolver, obj
         }
 
         // Deconstruct and add to multimap.
-        var pair = deconstructor.Deconstruct(resolver, genericTypes[0], genericTypes[1], value as string);
-        if (pair.Key != null)
+        foreach (var text in value as IEnumerable<string?> ?? [ value as string ])
         {
-            multimap.Add(pair);
+            var pair = deconstructor.Deconstruct(resolver, genericTypes[0], genericTypes[1], text);
+            if (pair.Key != null)
+            {
+                multimap.Add(pair);
+            }
         }
 
         return multimap;