ValidateSetAttribute enhancement: support set values to be dynamically generated from a custom ValidateSetValueGenerator

src/System.Management.Automation/engine/Attributes.cs

@@ -4,12 +4,15 @@
 
 using System.Collections;
 using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.Text.RegularExpressions;
 using System.Globalization;
 using System.Management.Automation.Internal;
 using System.Diagnostics.CodeAnalysis;
 using System.Management.Automation.Language;
 using System.Runtime.CompilerServices;
+using System.Linq;
+using System.Threading.Tasks;
 
 namespace System.Management.Automation.Internal
 {
@@ -1115,7 +1118,7 @@ public sealed class ValidatePatternAttribute : ValidateEnumeratedArgumentsAttrib
 
         /// <summary>
         /// Gets or sets the custom error message pattern that is displayed to the user.
-        /// 
+        ///
         /// The text representation of the object being validated and the validating regex is passed as
         /// the first and second formatting parameters to the ErrorMessage formatting pattern.
         /// <example>
@@ -1177,10 +1180,10 @@ public sealed class ValidateScriptAttribute : ValidateEnumeratedArgumentsAttribu
     {
         /// <summary>
         /// Gets or sets the custom error message that is displayed to the user.
-        /// 
+        ///
         /// The item being validated and the validating scriptblock is passed as the first and second
         /// formatting argument.
-        /// 
+        ///
         /// <example>
         /// [ValidateScript("$_ % 2", ErrorMessage = "The item '{0}' did not pass validation of script '{1}'")]
         /// </example>
@@ -1353,20 +1356,82 @@ public ValidateCountAttribute(int minLength, int maxLength)
         }
     }
 
+    /// <summary>
+    /// Optional base class for <see cref="IValidateSetValuesGenerator"/> implementations that want a default implementation to cache valid values.
+    /// </summary>
+    public abstract class CachedValidValuesGeneratorBase : IValidateSetValuesGenerator
+    {
+        // Cached valid values.
+        private string[] _validValues;
+        private int _validValuesCacheExpiration;
+
+        /// <summary>
+        /// Initializes a new instance of the CachedValidValuesGeneratorBase class.
+        /// </summary>
+        /// <param name="cacheExpirationInSeconds">Sets a time interval in seconds to reset the '_validValues' dynamic valid values cache.</param>
+        protected CachedValidValuesGeneratorBase(int cacheExpirationInSeconds)
+        {
+            _validValuesCacheExpiration = cacheExpirationInSeconds;
+        }
+
+        /// <summary>
+        /// Abstract method to generate a valid values.
+        /// </summary>
+        public abstract string[] GenerateValidValues();
+
+        /// <summary>
+        /// Get a valid values.
+        /// </summary>
+        public string[] GetValidValues()
+        {
+            // Because we have a background task to clear the cache by '_validValues = null'
+            // we use the local variable to exclude a race condition.
+            var validValuesLocal = _validValues;
+            if (validValuesLocal != null)
+            {
+                return validValuesLocal;
+            }
+
+            var validValuesNoCache = GenerateValidValues();
+
+            if (validValuesNoCache == null)
+            {
+                throw new ValidationMetadataException(
+                    "ValidateSetGeneratedValidValuesListIsNull",
+                    null,
+                    Metadata.ValidateSetGeneratedValidValuesListIsNull);
+            }
+
+            if (_validValuesCacheExpiration > 0)
+            {
+                _validValues = validValuesNoCache;
+                Task.Delay(_validValuesCacheExpiration * 1000).ContinueWith((task) => _validValues = null);
+            }
+
+            return validValuesNoCache;
+        }
+    }
+
     /// <summary>
     /// Validates that each parameter argument is present in a specified set
     /// </summary>
     [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
     public sealed class ValidateSetAttribute : ValidateEnumeratedArgumentsAttribute
     {
+        // We can use either static '_validValues'
+        // or dynamic valid values list generated by instance of 'validValuesGenerator'.
         private string[] _validValues;
+        private IValidateSetValuesGenerator validValuesGenerator = null;
+
+        // The valid values generator cache works across 'ValidateSetAttribute' instances.
+        private static ConcurrentDictionary<Type, IValidateSetValuesGenerator> s_ValidValuesGeneratorCache = new ConcurrentDictionary<Type, IValidateSetValuesGenerator>();
 
         /// <summary>
         /// Gets or sets the custom error message that is displayed to the user
-        /// 
+        ///
         /// The item being validated and a text representation of the validation set
         /// is passed as the first and second formatting argument to the ErrorMessage formatting pattern.
-        /// 
+        ///
         /// <example>
         /// [ValidateSet("A","B","C", ErrorMessage="The item '{0}' is not part of the set '{1}'.")
         /// </example>
@@ -1380,13 +1445,28 @@ public sealed class ValidateSetAttribute : ValidateEnumeratedArgumentsAttribute
         public bool IgnoreCase { get; set; } = true;
 
         /// <summary>
-        /// Gets the values in the set
+        /// Gets the valid values in the set.
         /// </summary>
         public IList<string> ValidValues
         {
             get
             {
-                return _validValues;
+                if (validValuesGenerator == null)
+                {
+                    return _validValues;
+                }
+
+                var validValuesLocal = validValuesGenerator.GetValidValues();
+
+                if (validValuesLocal == null)
+                {
+                    throw new ValidationMetadataException(
+                        "ValidateSetGeneratedValidValuesListIsNull",
+                        null,
+                        Metadata.ValidateSetGeneratedValidValuesListIsNull);
+                }
+
+                return validValuesLocal;
             }
         }
 
@@ -1409,16 +1489,13 @@ protected override void ValidateElement(object element)
             }
 
             string objString = element.ToString();
-            for (int setIndex = 0; setIndex < _validValues.Length; setIndex++)
+            foreach (string setString in ValidValues)
             {
-                string setString = _validValues[setIndex];
-
                 if (CultureInfo.InvariantCulture.
                         CompareInfo.Compare(setString, objString,
                                             IgnoreCase
                                                 ? CompareOptions.IgnoreCase
                                                 : CompareOptions.None) == 0)
-
                 {
                     return;
                 }
@@ -1455,6 +1532,37 @@ public ValidateSetAttribute(params string[] validValues)
 
             _validValues = validValues;
         }
+
+        /// <summary>
+        /// Initializes a new instance of the ValidateSetAttribute class.
+        /// Valid values is returned dynamically from a custom class implementing 'IValidateSetValuesGenerator' interface.
+        /// </summary>
+        /// <param name="valuesGeneratorType">class that implements the 'IValidateSetValuesGenerator' interface</param>
+        /// <exception cref="ArgumentException">for null arguments</exception>
+        public ValidateSetAttribute(Type valuesGeneratorType)
+        {
+            // We check 'IsNotPublic' because we don't want allow 'Activator.CreateInstance' create an instance of non-public type.
+            if (!typeof(IValidateSetValuesGenerator).IsAssignableFrom(valuesGeneratorType) || valuesGeneratorType.IsNotPublic)
+            {
+                throw PSTraceSource.NewArgumentException("valuesGeneratorType");
+            }
+
+            // Add a valid values generator to the cache.
+            // We don't cache valid values.
+            // We expect that valid values can be cached in the valid values generator.
+            validValuesGenerator = s_ValidValuesGeneratorCache.GetOrAdd(valuesGeneratorType, (key) => (IValidateSetValuesGenerator)Activator.CreateInstance(key));
+        }
+    }
+
+    /// <summary>
+    /// Allows dynamically generate set of values for ValidateSetAttribute.
+    /// </summary>
+    public interface IValidateSetValuesGenerator
+    {
+        /// <summary>
+        /// Get a valid values.
+        /// </summary>
+        string[] GetValidValues();
     }
 
     #region Allow

src/System.Management.Automation/engine/parser/Compiler.cs

@@ -1298,15 +1298,35 @@ private static Attribute NewAliasAttribute(AttributeAst ast)
 
         private static Attribute NewValidateSetAttribute(AttributeAst ast)
         {
+            ValidateSetAttribute result;
             var cvv = new ConstantValueVisitor { AttributeArgument = true };
-            var args = new string[ast.PositionalArguments.Count];
-            for (int i = 0; i < ast.PositionalArguments.Count; i++)
+
+            // 'ValidateSet([CustomGeneratorType], IgnoreCase=$false)' is supported in scripts.
+            if (ast.PositionalArguments.Count == 1 && ast.PositionalArguments[0] is TypeExpressionAst generatorTypeAst)
             {
-                args[i] = _attrArgToStringConverter.Target(_attrArgToStringConverter,
-                    ast.PositionalArguments[i].Accept(cvv));
+                if (TypeResolver.TryResolveType(generatorTypeAst.TypeName.FullName, out Type generatorType))
+                {
+                    result = new ValidateSetAttribute(generatorType);
+                }
+                else
+                {
+                    throw InterpreterError.NewInterpreterException(ast, typeof(RuntimeException), ast.Extent,
+                        "TypeNotFound", ParserStrings.TypeNotFound, generatorTypeAst.TypeName.FullName, typeof(System.Management.Automation.IValidateSetValuesGenerator).FullName);
+                }
+            }
+            else
+            {
+                // 'ValidateSet("value1","value2", IgnoreCase=$false)' is supported in scripts.
+                var args = new string[ast.PositionalArguments.Count];
+                for (int i = 0; i < ast.PositionalArguments.Count; i++)
+                {
+                    args[i] = _attrArgToStringConverter.Target(_attrArgToStringConverter,
+                        ast.PositionalArguments[i].Accept(cvv));
+                }
+
+                result = new ValidateSetAttribute(args);
             }
 
-            var result = new ValidateSetAttribute(args);
             foreach (var namedArg in ast.NamedArguments)
             {
                 var argValue = namedArg.Argument.Accept(cvv);
@@ -2998,7 +3018,7 @@ public object VisitPipeline(PipelineAst pipelineAst)
             {
                 var pipeElements = pipelineAst.PipelineElements;
                 var firstCommandExpr = (pipeElements[0] as CommandExpressionAst);
-    
+
                 if (firstCommandExpr != null && pipeElements.Count == 1)
                 {
                     if (firstCommandExpr.Redirections.Count > 0)
@@ -3014,7 +3034,7 @@ public object VisitPipeline(PipelineAst pipelineAst)
                 {
                     Expression input;
                     int i, commandsInPipe;
-    
+
                     if (firstCommandExpr != null)
                     {
                         if (firstCommandExpr.Redirections.Count > 0)
@@ -3035,24 +3055,24 @@ public object VisitPipeline(PipelineAst pipelineAst)
                         // here so that we can tell the difference b/w $null and no input when
                         // starting the pipeline, in other words, PipelineOps.InvokePipe will
                         // not pass this value to the pipe.
-    
+
                         input = ExpressionCache.AutomationNullConstant;
                         i = 0;
                         commandsInPipe = pipeElements.Count;
                     }
                     Expression[] pipelineExprs = new Expression[commandsInPipe];
                     CommandBaseAst[] pipeElementAsts = new CommandBaseAst[commandsInPipe];
                     var commandRedirections = new object[commandsInPipe];
-    
+
                     for (int j = 0; i < pipeElements.Count; ++i, ++j)
                     {
                         var pipeElement = pipeElements[i];
                         pipelineExprs[j] = Compile(pipeElement);
-    
+
                         commandRedirections[j] = GetCommandRedirections(pipeElement);
                         pipeElementAsts[j] = pipeElement;
                     }
-    
+
                     // The redirections are passed as a CommandRedirection[][] - one dimension for each command in the pipe,
                     // one dimension because each command may have multiple redirections.  Here we create the array for
                     // each command in the pipe, either a compile time constant or created at runtime if necessary.
@@ -3076,15 +3096,15 @@ public object VisitPipeline(PipelineAst pipelineAst)
                         // No redirections.
                         redirectionExpr = ExpressionCache.NullCommandRedirections;
                     }
-    
+
                     if (firstCommandExpr != null)
                     {
                         var inputTemp = Expression.Variable(input.Type);
                         temps.Add(inputTemp);
                         exprs.Add(Expression.Assign(inputTemp, input));
                         input = inputTemp;
                     }
-    
+
                     Expression invokePipe = Expression.Call(
                         CachedReflectionInfo.PipelineOps_InvokePipeline,
                         input.Cast(typeof(object)),

src/System.Management.Automation/resources/Metadata.resx

@@ -168,6 +168,9 @@
   <data name="ValidateSetFailure" xml:space="preserve">
     <value>The argument "{0}" does not belong to the set "{1}" specified by the ValidateSet attribute. Supply an argument that is in the set and then try the command again.</value>
   </data>
+  <data name="ValidateSetGeneratedValidValuesListIsNull" xml:space="preserve">
+    <value>Valid values generator return a null value.</value>
+  </data>
   <data name="ValidateFailureResult" xml:space="preserve">
     <value>"{0}" failed on property "{1}" {2}</value>
   </data>