Fix validator in new version of System.CommandLine

Author: sleeuwen

dotnet-json/Commands/FileArgument.cs

@@ -22,13 +22,15 @@ public FileArgument(string name, string? description = null)
         private void AddValidator()
         {
             this.AddValidator(symbol =>
-                symbol.Tokens
+            {
+                symbol.ErrorMessage ??= symbol.Tokens
                     .Select(t => t.Value)
                     .Where(_ => !AllowNewFile) // Need to check AllowNewFile at this point because AddValidator() is called from constructor
                     .Where(filePath => filePath != "-")
                     .Where(filePath => !File.Exists(filePath))
                     .Select(filePath => $"File does not exist: {filePath}")
-                    .FirstOrDefault());
+                    .FirstOrDefault();
+            });
         }
     }
 }

dotnet-json/Commands/FileOption.cs

@@ -25,13 +25,15 @@ public FileOption(string[] aliases, string? description = null)
         private void AddValidator()
         {
             this.AddValidator(symbol =>
-                symbol.Tokens
+            {
+                symbol.ErrorMessage ??= symbol.Tokens
                     .Select(t => t.Value)
                     .Where(_ => !AllowNewFile) // Need to check AllowNewFile at this point because AddValidator() is called from constructor
                     .Where(filePath => filePath != "-")
                     .Where(filePath => !File.Exists(filePath))
                     .Select(filePath => $"File does not exist: {filePath}")
-                    .FirstOrDefault());
+                    .FirstOrDefault();
+            });
         }
     }
 }

dotnet-json/Commands/FilesArgument.cs

@@ -23,13 +23,15 @@ public FilesArgument(string name, string? description = null)
         private void AddValidator()
         {
             this.AddValidator(symbol =>
-                symbol.Tokens
+            {
+                symbol.ErrorMessage ??= symbol.Tokens
                     .Select(t => t.Value)
                     .Where(_ => !AllowNewFile) // Need to check AllowNewFile at this point because AddValidator() is called from constructor
                     .Where(filePath => filePath != "-")
                     .Where(filePath => !File.Exists(filePath))
                     .Select(filePath => $"File does not exist: {filePath}")
-                    .FirstOrDefault());
+                    .FirstOrDefault();
+            });
         }
     }
 }

dotnet-json/Commands/RemoveCommand.cs

@@ -13,6 +13,11 @@ public class RemoveCommand : CommandBase, ICommandHandler
         public RemoveCommand()
             : base("remove", "Remove a value from the json")
         {
+            Key.AddValidator(symbol =>
+            {
+                if (symbol.Tokens.Count == 1 && string.IsNullOrEmpty(symbol.Tokens[0].Value))
+                    symbol.ErrorMessage = "Removing an empty key is not allowed.";
+            });
             AddArgument(Key);
 
             AddAlias("rm");