C# Bindings - Prompt formatting (#712)

* Added support for custom prompt formatting

* more docs added

* bump version

gpt4all-bindings/csharp/Directory.Build.props

@@ -5,7 +5,7 @@
         <Company></Company>
         <Copyright></Copyright>
         <NeutralLanguage>en-US</NeutralLanguage>
-        <Version>0.5.0</Version>
+        <Version>0.6.0</Version>
         <VersionSuffix>$(VersionSuffix)</VersionSuffix>
         <Version Condition=" '$(VersionSuffix)' != '' ">$(Version)$(VersionSuffix)</Version>
         <TreatWarningsAsErrors>true</TreatWarningsAsErrors>

gpt4all-bindings/csharp/Gpt4All/Gpt4All.cs

@@ -7,19 +7,33 @@ public class Gpt4All : IGpt4AllModel
 {
     private readonly ILLModel _model;
 
+    /// <inheritdoc/>
+    public IPromptFormatter? PromptFormatter { get; set; }
+
     internal Gpt4All(ILLModel model)
     {
         _model = model;
+        PromptFormatter = new DefaultPromptFormatter();
+    }
+
+    private string FormatPrompt(string prompt)
+    {
+        if (PromptFormatter == null) return prompt;
+
+        return PromptFormatter.FormatPrompt(prompt);
     }
 
     public Task<ITextPredictionResult> GetPredictionAsync(string text, PredictRequestOptions opts, CancellationToken cancellationToken = default)
     {
+        ArgumentNullException.ThrowIfNull(text);
+
         return Task.Run(() =>
         {
             var result = new TextPredictionResult();
             var context = opts.ToPromptContext();
+            var prompt = FormatPrompt(text);
 
-            _model.Prompt(text, context, responseCallback: e =>
+            _model.Prompt(prompt, context, responseCallback: e =>
             {
                 if (e.IsError)
                 {
@@ -37,6 +51,8 @@ public class Gpt4All : IGpt4AllModel
 
     public Task<ITextPredictionStreamingResult> GetStreamingPredictionAsync(string text, PredictRequestOptions opts, CancellationToken cancellationToken = default)
     {
+        ArgumentNullException.ThrowIfNull(text);
+
         var result = new TextPredictionStreamingResult();
 
         _ = Task.Run(() =>
@@ -44,8 +60,9 @@ public class Gpt4All : IGpt4AllModel
             try
             {
                 var context = opts.ToPromptContext();
+                var prompt = FormatPrompt(text);
 
-                _model.Prompt(text, context, responseCallback: e =>
+                _model.Prompt(prompt, context, responseCallback: e =>
                 {
                     if (e.IsError)
                     {

gpt4all-bindings/csharp/Gpt4All/Model/DefaultPromptFormatter.cs

@@ -0,0 +1,16 @@
+namespace Gpt4All;
+
+public class DefaultPromptFormatter : IPromptFormatter
+{
+    public string FormatPrompt(string prompt)
+    {
+        return $"""
+        ### Instruction: 
+        The prompt below is a question to answer, a task to complete, or a conversation
+        to respond to; decide which and write an appropriate response.
+        ### Prompt:
+        {prompt}
+        ### Response:
+        """;
+    }
+}

gpt4all-bindings/csharp/Gpt4All/Model/IGpt4AllModel.cs

@@ -2,4 +2,9 @@
 
 public interface IGpt4AllModel : ITextPrediction, IDisposable
 {
+    /// <summary>
+    /// The prompt formatter used to format the prompt before
+    /// feeding it to the model, if null no transformation is applied
+    /// </summary>
+    IPromptFormatter? PromptFormatter { get; set; }
 }

gpt4all-bindings/csharp/Gpt4All/Model/IPromptFormatter.cs

@@ -0,0 +1,14 @@
+namespace Gpt4All;
+
+/// <summary>
+/// Formats a prompt
+/// </summary>
+public interface IPromptFormatter
+{
+    /// <summary>
+    /// Format the provided prompt
+    /// </summary>
+    /// <param name="prompt">the input prompt</param>
+    /// <returns>The formatted prompt</returns>
+    string FormatPrompt(string prompt);
+}