Add Default Syntax and Supported Syntax activity property attributes

src/core/Elsa.Abstractions/Attributes/ActivityPropertyAttribute.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 
 namespace Elsa.Attributes
 {
@@ -49,5 +50,15 @@ namespace Elsa.Attributes
         /// The type that provides a default value.
         /// </summary>
         public Type? DefaultValueProvider { get; set; }
+        
+        /// <summary>
+        /// The syntax to use by default when evaluating the value. Only used when the property definition doesn't have a syntax specified. 
+        /// </summary>
+        public string? DefaultSyntax { get; set; }
+        
+        /// <summary>
+        /// The syntax to use by default when evaluating the value. Only used when the property definition doesn't have a syntax specified. 
+        /// </summary>
+        public string[]? SupportedSyntaxes { get; set; }
     }
 }

src/core/Elsa.Abstractions/Metadata/ActivityPropertyDescriptor.cs

@@ -1,3 +1,7 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
 namespace Elsa.Metadata
 {
     public class ActivityPropertyDescriptor
@@ -6,23 +10,39 @@ namespace Elsa.Metadata
         {
         }
 
-        public ActivityPropertyDescriptor(string name, string uiHint, string label, string? hint = default, object? options = default, string? category = default, object? defaultValue = default)
+        public ActivityPropertyDescriptor(
+            string name,
+            Type type,
+            string uiHint,
+            string label,
+            string? hint = default,
+            object? options = default,
+            string? category = default,
+            object? defaultValue = default,
+            string? defaultSyntax = "Literal",
+            IEnumerable<string>? supportedSyntaxes = default)
         {
             Name = name;
+            Type = type;
             UIHint = uiHint;
             Label = label;
             Hint = hint;
             Options = options;
             Category = category;
             DefaultValue = defaultValue;
+            DefaultSyntax = defaultSyntax;
+            SupportedSyntaxes = supportedSyntaxes?.ToList() ?? new List<string>();
         }
-        
+
         public string Name { get; set; } = default!;
+        public Type Type { get; set; } = default!;
         public string UIHint { get; set; } = default!;
         public string Label { get; set; } = default!;
         public string? Hint { get; set; }
         public object? Options { get; set; }
         public string? Category { get; set; }
         public object? DefaultValue { get; set; }
+        public string? DefaultSyntax { get; set; }
+        public IList<string> SupportedSyntaxes { get; set; } = new List<string>();
     }
 }

src/core/Elsa.Core/Metadata/TypedActivityTypeDescriber.cs

@@ -57,12 +57,15 @@ namespace Elsa.Metadata
                 yield return new ActivityPropertyDescriptor
                 (
                     (activityPropertyAttribute.Name ?? propertyInfo.Name).Pascalize(),
+                    propertyInfo.PropertyType,
                     _uiHintResolver.GetUIHint(propertyInfo),
                     activityPropertyAttribute.Label ?? propertyInfo.Name.Humanize(LetterCasing.Title),
                     activityPropertyAttribute.Hint,
                     _optionsResolver.GetOptions(propertyInfo),
                     activityPropertyAttribute.Category,
-                    _defaultValueResolver.GetDefaultValue(propertyInfo)
+                    _defaultValueResolver.GetDefaultValue(propertyInfo),
+                    activityPropertyAttribute.DefaultSyntax,
+                    activityPropertyAttribute.SupportedSyntaxes
                 );
             }
         }

src/core/Elsa.Core/Services/WorkflowBlueprintMaterializer.cs

@@ -6,6 +6,7 @@ using System.Threading;
 using System.Threading.Tasks;
 using Elsa.ActivityProviders;
 using Elsa.Builders;
+using Elsa.Expressions;
 using Elsa.Models;
 using Elsa.Services.Models;
 using Microsoft.Extensions.DependencyInjection;
@@ -73,20 +74,21 @@ namespace Elsa.Services
             foreach (var activityDefinition in activityDefinitions)
             {
                 var activityType = await _activityTypeService.GetActivityTypeAsync(activityDefinition.Type, cancellationToken);
-                var type = activityType.Type;
-                var props = type.GetProperties();
+                var activityDescriptor = activityType.Describe();
+                var propertyDescriptors = activityDescriptor.Properties;
 
                 foreach (var property in activityDefinition.Properties)
                 {
-                    var prop = props.FirstOrDefault(x => x.Name == property.Name);
-
-                    if (prop == null)
+                    var propertyDescriptor = propertyDescriptors.FirstOrDefault(x => x.Name == property.Name);
+                    
+                    if (propertyDescriptor == null)
                     {
-                        _logger.LogWarning("Could not find the specified property '{PropertyName}' for activity type {ActivityTypeName}. Was the activity property renamed/removed/refactored after the workflow definition was created?", property.Name, activityType.Type.Name);
+                        _logger.LogWarning("Could not find the specified property '{PropertyName}' for activity type {ActivityTypeName}", property.Name, activityType.TypeName);
                         continue;
                     }
 
-                    var provider = new ExpressionActivityPropertyValueProvider(property.Expression, property.Syntax ?? "Literal", prop.PropertyType);
+                    var syntax = property.Syntax ?? propertyDescriptor.DefaultSyntax ?? SyntaxNames.Literal;
+                    var provider = new ExpressionActivityPropertyValueProvider(property.Expression, syntax, propertyDescriptor.Type);
                     propertyProviders.AddProvider(activityDefinition.ActivityId, property.Name, provider);
                 }
             }