expose Argument.Validators, remove AddValidator helper method

src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt

@@ -4,6 +4,7 @@ System.CommandLine
     public System.Collections.Generic.ICollection<System.Func<System.CommandLine.Completions.CompletionContext,System.Collections.Generic.IEnumerable<System.CommandLine.Completions.CompletionItem>>> Completions { get; }
     public System.Boolean HasDefaultValue { get; }
     public System.String HelpName { get; set; }
+    public System.Collections.Generic.List<System.Action<System.CommandLine.Parsing.ArgumentResult>> Validators { get; }
     public System.Type ValueType { get; }
     public System.Collections.Generic.IEnumerable<System.CommandLine.Completions.CompletionItem> GetCompletions(System.CommandLine.Completions.CompletionContext context)
     public System.Object GetDefaultValue()
@@ -26,7 +27,6 @@ System.CommandLine
     public Argument<T> AddCompletions(System.String[] completions)
     public Argument<T> AddCompletions(System.Func<System.CommandLine.Completions.CompletionContext,System.Collections.Generic.IEnumerable<System.String>> completionsDelegate)
     public Argument<T> AddCompletions(System.Func<System.CommandLine.Completions.CompletionContext,System.Collections.Generic.IEnumerable<System.CommandLine.Completions.CompletionItem>> completionsDelegate)
-    public Argument<T> AddValidator(System.Action<System.CommandLine.Parsing.ArgumentResult> validate)
     public System.Void SetDefaultValue(T value)
     public System.Void SetDefaultValueFactory(Func<T> defaultValueFactory)
     public System.Void SetDefaultValueFactory(Func<System.CommandLine.Parsing.ArgumentResult,T> defaultValueFactory)

src/System.CommandLine.Tests/ArgumentTests.cs

@@ -792,7 +792,6 @@ public void Argument_of_T_fluent_APIs_return_Argument_of_T()
                 .AddCompletions("test")
                 .AddCompletions(ctx => Array.Empty<string>())
                 .AddCompletions(ctx => Array.Empty<CompletionItem>())
-                .AddValidator(_ => { })
                 .AcceptLegalFileNamesOnly()
                 .AcceptLegalFilePathsOnly();
 

src/System.CommandLine.Tests/ParsingValidationTests.cs

@@ -327,7 +327,7 @@ public void A_custom_validator_can_be_added_to_an_argument()
         {
             var argument = new Argument<int>("x");
 
-            argument.AddValidator(r =>
+            argument.Validators.Add(r =>
             {
                 var value = r.GetValueOrDefault<int>();
 
@@ -365,7 +365,7 @@ public void All_custom_validators_are_called(string commandLine)
             });
 
             var argument = new Argument<string>("the-arg");
-            argument.AddValidator(_ =>
+            argument.Validators.Add(_ =>
             {
                 argumentValidatorWasCalled = true;
             });
@@ -460,7 +460,7 @@ public void Custom_validator_error_messages_are_not_repeated()
         {
             var errorMessage = "that's not right...";
             var argument = new Argument<string>();
-            argument.AddValidator(r => r.ErrorMessage = errorMessage);
+            argument.Validators.Add(r => r.ErrorMessage = errorMessage);
 
             var cmd = new Command("get")
             {
@@ -481,7 +481,7 @@ public void The_parsed_value_of_an_argument_is_available_within_a_validator()
         {
             var argument = new Argument<int>();
             var errorMessage = "The value of option '-x' must be between 1 and 100.";
-            argument.AddValidator(result =>
+            argument.Validators.Add(result =>
             {
                 var value = result.GetValue(argument);
 
@@ -1162,8 +1162,8 @@ public void Multiple_validators_on_the_same_option_do_not_report_duplicate_error
         public void Multiple_validators_on_the_same_argument_do_not_report_duplicate_errors()
         {
             var argument = new Argument<string>();
-            argument.AddValidator(result => result.ErrorMessage = "Wrong");
-            argument.AddValidator(_ => { });
+            argument.Validators.Add(result => result.ErrorMessage = "Wrong");
+            argument.Validators.Add(_ => { });
 
             var command = new RootCommand
             {

src/System.CommandLine/Argument.cs

@@ -103,7 +103,11 @@ private protected override string DefaultName
             }
         }
 
-        internal List<Action<ArgumentResult>> Validators => _validators ??= new ();
+        /// <summary>
+        /// Provides a list of argument validators. Validators can be used
+        /// to provide custom errors based on user input.
+        /// </summary>
+        public List<Action<ArgumentResult>> Validators => _validators ??= new ();
 
         /// <summary>
         /// Gets the default value for the argument.

src/System.CommandLine/ArgumentValidation.cs

@@ -18,7 +18,7 @@ public static class ArgumentValidation
         /// <returns>The configured argument.</returns>
         public static Argument<FileInfo> AcceptExistingOnly(this Argument<FileInfo> argument)
         {
-            argument.AddValidator(Validate.FileExists);
+            argument.Validators.Add(Validate.FileExists);
             return argument;
         }
 
@@ -29,7 +29,7 @@ public static Argument<FileInfo> AcceptExistingOnly(this Argument<FileInfo> argu
         /// <returns>The configured argument.</returns>
         public static Argument<DirectoryInfo> AcceptExistingOnly(this Argument<DirectoryInfo> argument)
         {
-            argument.AddValidator(Validate.DirectoryExists);
+            argument.Validators.Add(Validate.DirectoryExists);
             return argument;
         }
 
@@ -40,7 +40,7 @@ public static Argument<DirectoryInfo> AcceptExistingOnly(this Argument<Directory
         /// <returns>The configured argument.</returns>
         public static Argument<FileSystemInfo> AcceptExistingOnly(this Argument<FileSystemInfo> argument)
         {
-            argument.AddValidator(Validate.FileOrDirectoryExists);
+            argument.Validators.Add(Validate.FileOrDirectoryExists);
             return argument;
         }
 
@@ -54,15 +54,15 @@ public static Argument<T> AcceptExistingOnly<T>(this Argument<T> argument)
         {
             if (typeof(IEnumerable<FileInfo>).IsAssignableFrom(typeof(T)))
             {
-                argument.AddValidator(Validate.FileExists);
+                argument.Validators.Add(Validate.FileExists);
             }
             else if (typeof(IEnumerable<DirectoryInfo>).IsAssignableFrom(typeof(T)))
             {
-                argument.AddValidator(Validate.DirectoryExists);
+                argument.Validators.Add(Validate.DirectoryExists);
             }
             else
             {
-                argument.AddValidator(Validate.FileOrDirectoryExists);
+                argument.Validators.Add(Validate.FileOrDirectoryExists);
             }
 
             return argument;

src/System.CommandLine/Argument{T}.cs

@@ -205,17 +205,6 @@ public Argument<T> AddCompletions(Func<CompletionContext, IEnumerable<Completion
             return this;
         }
 
-        /// <summary>
-        /// Adds a custom validator to the argument. Validators can be used
-        /// to provide custom errors based on user input.
-        /// </summary>
-        /// <param name="validate">The action to validate the parsed argument.</param>
-        public Argument<T> AddValidator(Action<ArgumentResult> validate)
-        {
-            Validators.Add(validate);
-            return this;
-        }
-
         /// <summary>
         /// Configures the argument to accept only the specified values, and to suggest them as command line completions.
         /// </summary>
@@ -239,7 +228,7 @@ public Argument<T> AcceptLegalFilePathsOnly()
         {
             var invalidPathChars = Path.GetInvalidPathChars();
 
-            AddValidator(result =>
+            Validators.Add(result =>
             {
                 for (var i = 0; i < result.Tokens.Count; i++)
                 {
@@ -268,7 +257,7 @@ public Argument<T> AcceptLegalFileNamesOnly()
         {
             var invalidFileNameChars = Path.GetInvalidFileNameChars();
 
-            AddValidator(result =>
+            Validators.Add(result =>
             {
                 for (var i = 0; i < result.Tokens.Count; i++)
                 {