.Net: Support for primitives and complex types by Kernel prompt template

dotnet/src/SemanticKernel.Abstractions/Functions/IKernelPluginExtensions.cs

@@ -56,7 +56,7 @@ public static KernelFunction GetFunction(this IReadOnlyKernelPluginCollection pl
 
         if (!TryGetFunction(plugins, pluginName, functionName, out KernelFunction? function))
         {
-            throw new KeyNotFoundException("The plugin collection does not contain a plugin and/or function with the specified names.");
+            throw new KeyNotFoundException($"The plugin collection does not contain a plugin and/or function with the specified names. Plugin name - '{pluginName}', function name - '{functionName}'.");
         }
 
         return function;

dotnet/src/SemanticKernel.Core/PromptTemplate/KernelPromptTemplate.cs

@@ -1,8 +1,10 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
-using System.Linq;
+using System.ComponentModel;
+using System.Globalization;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -45,9 +47,6 @@ public KernelPromptTemplate(PromptTemplateConfig promptConfig, ILoggerFactory? l
     /// <inheritdoc/>
     public Task<string> RenderAsync(Kernel kernel, KernelArguments? arguments = null, CancellationToken cancellationToken = default)
     {
-        // Make sure all arguments are of string type. This is temporary check until non-string arguments are supported.
-        AssertArgumentOfStringType(arguments);
-
         return this.RenderAsync(this._blocks.Value, kernel, arguments, cancellationToken);
     }
 
@@ -64,7 +63,7 @@ public Task<string> RenderAsync(Kernel kernel, KernelArguments? arguments = null
     /// <param name="templateText">Prompt template (see skprompt.txt files)</param>
     /// <param name="validate">Whether to validate the blocks syntax, or just return the blocks found, which could contain invalid code</param>
     /// <returns>A list of all the blocks, ie the template tokenized in text, variables and function calls</returns>
-    internal List<Block> ExtractBlocks(string? templateText, bool validate = true)
+    private List<Block> ExtractBlocks(string? templateText, bool validate = true)
     {
         this._logger.LogTrace("Extracting blocks from template: {0}", templateText);
         var blocks = this._tokenizer.Tokenize(templateText);
@@ -91,7 +90,7 @@ internal List<Block> ExtractBlocks(string? templateText, bool validate = true)
     /// <param name="arguments">The arguments.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>The prompt template ready to be used for an AI request.</returns>
-    internal async Task<string> RenderAsync(List<Block> blocks, Kernel kernel, KernelArguments? arguments, CancellationToken cancellationToken = default)
+    private async Task<string> RenderAsync(List<Block> blocks, Kernel kernel, KernelArguments? arguments, CancellationToken cancellationToken = default)
     {
         this._logger.LogTrace("Rendering list of {0} blocks", blocks.Count);
 
@@ -101,11 +100,11 @@ internal async Task<string> RenderAsync(List<Block> blocks, Kernel kernel, Kerne
             switch (block)
             {
                 case ITextRendering staticBlock:
-                    result.Append(staticBlock.Render(arguments));
+                    result.Append(ConvertToString(staticBlock.Render(arguments), kernel.Culture));
                     break;
 
                 case ICodeRendering dynamicBlock:
-                    result.Append(await dynamicBlock.RenderCodeAsync(kernel, arguments, cancellationToken).ConfigureAwait(false));
+                    result.Append(ConvertToString(await dynamicBlock.RenderCodeAsync(kernel, arguments, cancellationToken).ConfigureAwait(false), kernel.Culture));
                     break;
 
                 default:
@@ -123,42 +122,42 @@ internal async Task<string> RenderAsync(List<Block> blocks, Kernel kernel, Kerne
         return resultString;
     }
 
-    /// <summary>
-    /// Given a list of blocks, render the Variable Blocks, replacing placeholders with the actual value in memory.
-    /// </summary>
-    /// <param name="blocks">List of blocks, typically all the blocks found in a template.</param>
-    /// <param name="arguments">Arguments to use for rendering.</param>
-    /// <returns>An updated list of blocks where Variable Blocks have rendered to Text Blocks.</returns>
-    internal IList<Block> RenderVariables(IList<Block> blocks, KernelArguments? arguments)
+    private static string? ConvertToString(object? value, CultureInfo culture)
     {
-        this._logger.LogTrace("Rendering variables");
-        return blocks.Select(block => block.Type != BlockTypes.Variable
-            ? block
-            : new TextBlock(((ITextRendering)block).Render(arguments), this._loggerFactory)).ToList();
+        if (value == null) { return null; }
+
+        var sourceType = value.GetType();
+
+        var converterFunction = GetTypeConverterDelegate(sourceType);
+
+        return converterFunction == null
+            ? value.ToString()
+            : converterFunction(value, culture);
     }
 
-    /// <summary>
-    /// Validates that all the KernelArguments are of string type.
-    /// </summary>
-    /// <param name="arguments">The collection of KernelArguments to validate.</param>
-    /// <exception cref="KernelException">Thrown when an argument is not of type string.</exception>
-    private static void AssertArgumentOfStringType(KernelArguments? arguments)
-    {
-        if (arguments == null)
+    private static Func<object?, CultureInfo, string?>? GetTypeConverterDelegate(Type sourceType) =>
+        s_converters.GetOrAdd(sourceType, static sourceType =>
         {
-            return;
-        }
+            // Strings just render as themselves.
+            if (sourceType == typeof(string))
+            {
+                return (input, cultureInfo) => (string)input!;
+            }
 
-        foreach (var argument in arguments)
-        {
-            if (argument.Value is string)
+            // Look up and use a type converter.
+            if (TypeConverterFactory.GetTypeConverter(sourceType) is TypeConverter converter && converter.CanConvertTo(typeof(string)))
             {
-                continue;
+                return (input, cultureInfo) =>
+                {
+                    return converter.ConvertToString(context: null, cultureInfo, input);
+                };
             }
 
-            throw new KernelException($"Non-string kernel prompt template arguments are not supported in Release Candidate 1. This feature will be available soon, but for now, please ensure that all arguments are strings. Argument '{argument.Key}' is of type '{argument.Value?.GetType()}'.");
-        }
-    }
+            return null;
+        });
+
+    /// <summary>Converter functions for converting types to strings.</summary>
+    private static readonly ConcurrentDictionary<Type, Func<object?, CultureInfo, string?>?> s_converters = new();
 
     #endregion
 }

dotnet/src/SemanticKernel.Core/TemplateEngine/Blocks/CodeBlock.cs

@@ -70,7 +70,7 @@ public override bool IsValid(out string errorMsg)
     }
 
     /// <inheritdoc/>
-    public ValueTask<string> RenderCodeAsync(Kernel kernel, KernelArguments? arguments = null, CancellationToken cancellationToken = default)
+    public ValueTask<object?> RenderCodeAsync(Kernel kernel, KernelArguments? arguments = null, CancellationToken cancellationToken = default)
     {
         if (!this._validated && !this.IsValid(out var error))
         {
@@ -81,7 +81,7 @@ public ValueTask<string> RenderCodeAsync(Kernel kernel, KernelArguments? argumen
 
         return this._tokens[0].Type switch
         {
-            BlockTypes.Value or BlockTypes.Variable => new ValueTask<string>(((ITextRendering)this._tokens[0]).Render(arguments)),
+            BlockTypes.Value or BlockTypes.Variable => new ValueTask<object?>(((ITextRendering)this._tokens[0]).Render(arguments)),
             BlockTypes.FunctionId => this.RenderFunctionCallAsync((FunctionIdBlock)this._tokens[0], kernel, arguments),
             _ => throw new KernelException($"Unexpected first token type: {this._tokens[0].Type:G}"),
         };
@@ -92,7 +92,7 @@ public ValueTask<string> RenderCodeAsync(Kernel kernel, KernelArguments? argumen
     private bool _validated;
     private readonly List<Block> _tokens;
 
-    private async ValueTask<string> RenderFunctionCallAsync(FunctionIdBlock fBlock, Kernel kernel, KernelArguments? arguments)
+    private async ValueTask<object?> RenderFunctionCallAsync(FunctionIdBlock fBlock, Kernel kernel, KernelArguments? arguments)
     {
         // If the code syntax is {{functionName $varName}} use $varName instead of $input
         // If the code syntax is {{functionName 'value'}} use "value" instead of $input
@@ -104,7 +104,7 @@ private async ValueTask<string> RenderFunctionCallAsync(FunctionIdBlock fBlock,
         {
             var result = await kernel.InvokeAsync(fBlock.PluginName, fBlock.FunctionName, arguments).ConfigureAwait(false);
 
-            return result.ToString();
+            return result.Value;
         }
         catch (Exception ex)
         {
@@ -154,7 +154,7 @@ private KernelArguments EnrichFunctionArguments(KernelArguments arguments)
         var namedArgsStartIndex = 1;
         if (firstArg.Type is not BlockTypes.NamedArg)
         {
-            string input = ((ITextRendering)this._tokens[1]).Render(arguments);
+            object? input = ((ITextRendering)this._tokens[1]).Render(arguments);
             // Keep previous trust information when updating the input
             arguments[KernelArguments.InputParameterName] = input;
             namedArgsStartIndex++;

dotnet/src/SemanticKernel.Core/TemplateEngine/Blocks/FunctionIdBlock.cs

@@ -53,7 +53,7 @@ public override bool IsValid(out string errorMsg)
     }
 
     /// <inheritdoc/>
-    public string Render(KernelArguments? arguments)
+    public object? Render(KernelArguments? arguments)
     {
         return this.Content;
     }

dotnet/src/SemanticKernel.Core/TemplateEngine/Blocks/ICodeRendering.cs

@@ -17,5 +17,5 @@ internal interface ICodeRendering
     /// <param name="arguments">The arguments</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>Rendered content</returns>
-    public ValueTask<string> RenderCodeAsync(Kernel kernel, KernelArguments? arguments = null, CancellationToken cancellationToken = default);
+    public ValueTask<object?> RenderCodeAsync(Kernel kernel, KernelArguments? arguments = null, CancellationToken cancellationToken = default);
 }

dotnet/src/SemanticKernel.Core/TemplateEngine/Blocks/ITextRendering.cs

@@ -11,5 +11,5 @@ internal interface ITextRendering
     /// </summary>
     /// <param name="arguments">Optional arguments the block rendering</param>
     /// <returns>Rendered content</returns>
-    public string Render(KernelArguments? arguments);
+    public object? Render(KernelArguments? arguments);
 }

dotnet/src/SemanticKernel.Core/TemplateEngine/Blocks/NamedArgBlock.cs

@@ -62,7 +62,7 @@ public NamedArgBlock(string? text, ILoggerFactory? logger = null)
     /// </summary>
     /// <param name="arguments">Arguments to use for rendering the named argument value when the value is a <see cref="VarBlock"/>.</param>
     /// <returns></returns>
-    internal string GetValue(KernelArguments? arguments)
+    internal object? GetValue(KernelArguments? arguments)
     {
         var valueIsValidValBlock = this._valBlock != null && this._valBlock.IsValid(out var errorMessage);
         if (valueIsValidValBlock)
@@ -80,7 +80,7 @@ internal string GetValue(KernelArguments? arguments)
     }
 
     /// <inheritdoc/>
-    public string Render(KernelArguments? arguments)
+    public object? Render(KernelArguments? arguments)
     {
         return this.Content;
     }

dotnet/src/SemanticKernel.Core/TemplateEngine/Blocks/TextBlock.cs

@@ -25,7 +25,7 @@ public override bool IsValid(out string errorMsg)
     }
 
     /// <inheritdoc/>
-    public string Render(KernelArguments? arguments)
+    public object? Render(KernelArguments? arguments)
     {
         return this.Content;
     }

dotnet/src/SemanticKernel.Core/TemplateEngine/Blocks/ValBlock.cs

@@ -61,7 +61,7 @@ public override bool IsValid(out string errorMsg)
 #pragma warning restore CA2254
 
     /// <inheritdoc/>
-    public string Render(KernelArguments? arguments)
+    public object? Render(KernelArguments? arguments)
     {
         return this._value;
     }

dotnet/src/SemanticKernel.Core/TemplateEngine/Blocks/VarBlock.cs

@@ -62,7 +62,7 @@ public override bool IsValid(out string errorMsg)
 #pragma warning restore CA2254
 
     /// <inheritdoc/>
-    public string Render(KernelArguments? arguments)
+    public object? Render(KernelArguments? arguments)
     {
         if (arguments == null) { return string.Empty; }
 
@@ -75,7 +75,7 @@ public string Render(KernelArguments? arguments)
 
         if (arguments.TryGetValue(this.Name, out object? value))
         {
-            return (string?)value ?? string.Empty;
+            return value ?? string.Empty;
         }
 
         this.Logger.LogWarning("Variable `{0}{1}` not found", Symbols.VarPrefix, this.Name);