Validate that commands have unique names

Author: Tyrrrz

CliFx.Generators/CommandDescriptorGenerator.cs

@@ -105,6 +105,32 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                 .Collect(),
             static (ctx, commands) =>
             {
+                // Validate that all commands have unique names
+                foreach (var (i, first) in commands.Index())
+                {
+                    foreach (var second in commands.Skip(i + 1))
+                    {
+                        if (
+                            string.Equals(
+                                first.Name,
+                                second.Name,
+                                System.StringComparison.OrdinalIgnoreCase
+                            )
+                        )
+                        {
+                            ctx.ReportDiagnostic(
+                                Diagnostic.Create(
+                                    DiagnosticDescriptors.CommandMustHaveUniqueName,
+                                    second.Type.Locations.FirstOrDefault(),
+                                    second.Type.Name,
+                                    first.Type.Name,
+                                    first.Name ?? "<default>"
+                                )
+                            );
+                        }
+                    }
+                }
+
                 ctx.AddSource(
                     "CommandRegistrations.g.cs",
                     SourceText.From(CommandRegistration.Emit(commands), Encoding.UTF8)

CliFx.Generators/DiagnosticDescriptors.cs

@@ -26,6 +26,16 @@ public static class DiagnosticDescriptors
             true
         );
 
+    public static DiagnosticDescriptor CommandMustHaveUniqueName { get; } =
+        new(
+            $"{nameof(CliFx)}_{nameof(CommandMustHaveUniqueName)}",
+            "Command must have a unique name",
+            "Command bound to type '{0}' has the same name as the command bound to type '{1}': '{2}'. All commands registered in an application must have unique names (comparison IS NOT case-sensitive).",
+            "CliFx",
+            DiagnosticSeverity.Error,
+            true
+        );
+
     // Inputs
 
     public static DiagnosticDescriptor CommandInputConverterNotInferrable { get; } =