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.Net: Update LiquidPromptTemplate to use Fluid instead of Scriban (#6320
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)

Closes #6233
cc: @sebastienros, @LittleLittleCloud, @JakeRadMSFT

---------

Co-authored-by: Mark Wallace <127216156+markwallace-microsoft@users.noreply.github.com>
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@stephentoub @markwallace-microsoft
stephentoub and markwallace-microsoft committed May 27, 2024
1 parent 6551546 commit 44d20c0
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Showing 3 changed files with 69 additions and 37 deletions.
2 changes: 1 addition & 1 deletion dotnet/Directory.Packages.props
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Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,7 @@
<PackageVersion Include="protobuf-net" Version="3.2.30" />
<PackageVersion Include="protobuf-net.Reflection" Version="3.2.12" />
<PackageVersion Include="YamlDotNet" Version="15.1.2" />
<PackageVersion Include="Scriban" Version="5.10.0" />
<PackageVersion Include="Fluid.Core" Version="2.10.0" />
<!-- Memory stores -->
<PackageVersion Include="Microsoft.Azure.Cosmos" Version="3.41.0-preview.0" />
<PackageVersion Include="Pgvector" Version="0.2.0" />
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102 changes: 67 additions & 35 deletions dotnet/src/Extensions/PromptTemplates.Liquid/LiquidPromptTemplate.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,14 +2,13 @@

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
using Scriban;
using Scriban.Syntax;
using Fluid;
using Fluid.Ast;

namespace Microsoft.SemanticKernel.PromptTemplates.Liquid;

Expand All @@ -18,12 +17,18 @@ namespace Microsoft.SemanticKernel.PromptTemplates.Liquid;
/// </summary>
internal sealed partial class LiquidPromptTemplate : IPromptTemplate
{
private static readonly FluidParser s_parser = new();
private static readonly TemplateOptions s_templateOptions = new()
{
MemberAccessStrategy = new UnsafeMemberAccessStrategy() { MemberNameStrategy = MemberNameStrategies.SnakeCase },
};

private const string ReservedString = "&#58;";
private const string ColonString = ":";
private const char LineEnding = '\n';
private readonly PromptTemplateConfig _config;
private readonly bool _allowDangerouslySetContent;
private readonly Template _liquidTemplate;
private readonly IFluidTemplate _liquidTemplate;
private readonly Dictionary<string, object> _inputVariables;

#if NET
Expand Down Expand Up @@ -55,12 +60,12 @@ public LiquidPromptTemplate(PromptTemplateConfig config, bool allowDangerouslySe

// Parse the template now so we can check for errors, understand variable usage, and
// avoid having to parse on each render.
this._liquidTemplate = Template.ParseLiquid(config.Template);
if (this._liquidTemplate.HasErrors)
if (!s_parser.TryParse(config.Template, out this._liquidTemplate, out string error))
{
throw new ArgumentException($"The template could not be parsed:{Environment.NewLine}{string.Join(Environment.NewLine, this._liquidTemplate.Messages)}");
throw new ArgumentException(error is not null ?
$"The template could not be parsed:{Environment.NewLine}{error}" :
"The template could not be parsed.");
}
Debug.Assert(this._liquidTemplate.Page is not null);

// Ideally the prompty author would have explicitly specified input variables. If they specified any,
// assume they specified them all. If they didn't, heuristically try to find the variables, looking for
Expand Down Expand Up @@ -92,7 +97,7 @@ public async Task<string> RenderAsync(Kernel kernel, KernelArguments? arguments
{
Verify.NotNull(kernel);
cancellationToken.ThrowIfCancellationRequested();
var variables = this.GetVariables(arguments);
var variables = this.GetTemplateContext(arguments);
var renderedResult = this._liquidTemplate.Render(variables);

// parse chat history
Expand Down Expand Up @@ -154,9 +159,9 @@ private string ReplaceReservedStringBackToColonIfNeeded(string text)
/// <summary>
/// Gets the variables for the prompt template, including setting any default values from the prompt config.
/// </summary>
private Dictionary<string, object?> GetVariables(KernelArguments? arguments)
private TemplateContext GetTemplateContext(KernelArguments? arguments)
{
var result = new Dictionary<string, object?>();
var ctx = new TemplateContext(s_templateOptions);

foreach (var p in this._config.InputVariables)
{
Expand All @@ -165,7 +170,7 @@ private string ReplaceReservedStringBackToColonIfNeeded(string text)
continue;
}

result[p.Name] = p.Default;
ctx.SetValue(p.Name, p.Default);
}

if (arguments is not null)
Expand All @@ -177,17 +182,17 @@ private string ReplaceReservedStringBackToColonIfNeeded(string text)
var value = (object)kvp.Value;
if (this.ShouldReplaceColonToReservedString(this._config, kvp.Key, kvp.Value))
{
result[kvp.Key] = value.ToString()?.Replace(ColonString, ReservedString);
ctx.SetValue(kvp.Key, value.ToString()?.Replace(ColonString, ReservedString));
}
else
{
result[kvp.Key] = value;
ctx.SetValue(kvp.Key, value);
}
}
}
}

return result;
return ctx;
}

private bool ShouldReplaceColonToReservedString(PromptTemplateConfig promptTemplateConfig, string propertyName, object? propertyValue)
Expand All @@ -209,20 +214,23 @@ private bool ShouldReplaceColonToReservedString(PromptTemplateConfig promptTempl
}

/// <summary>
/// Visitor for <see cref="ScriptPage"/> looking for variables that are only
/// Visitor for <see cref="IFluidTemplate"/> looking for variables that are only
/// ever read and appear to represent very simple strings. If any variables
/// other than that are found, none are returned.
/// other than that are found, none are returned. This only handles very basic
/// cases where the template doesn't contain any more complicated constructs;
/// the heuristic can be improved over time.
/// </summary>
private sealed class SimpleVariablesVisitor : ScriptVisitor
private sealed class SimpleVariablesVisitor : AstVisitor
{
private readonly HashSet<string> _variables = new(StringComparer.OrdinalIgnoreCase);
private readonly Stack<Statement> _statementStack = new();
private bool _valid = true;

public static HashSet<string> InferInputs(Template template)
public static HashSet<string> InferInputs(IFluidTemplate template)
{
var visitor = new SimpleVariablesVisitor();

template.Page.Accept(visitor);
visitor.VisitTemplate(template);
if (!visitor._valid)
{
visitor._variables.Clear();
Expand All @@ -231,27 +239,51 @@ public static HashSet<string> InferInputs(Template template)
return visitor._variables;
}

public override void Visit(ScriptVariableGlobal node)
public override Statement Visit(Statement statement)
{
if (!this._valid)
{
return statement;
}

this._statementStack.Push(statement);
try
{
return base.Visit(statement);
}
finally
{
this._statementStack.Pop();
}
}

protected override Expression VisitMemberExpression(MemberExpression memberExpression)
{
if (this._valid)
if (memberExpression.Segments.Count == 1 && memberExpression.Segments[0] is IdentifierSegment id)
{
switch (node.Parent)
bool isValid = true;

if (this._statementStack.Count > 0)
{
case ScriptAssignExpression assign when ReferenceEquals(assign.Target, node):
case ScriptForStatement forLoop:
case ScriptMemberExpression member:
// Unsupported use found; bail.
this._valid = false;
return;

default:
// Reading from a simple variable.
this._variables.Add(node.Name);
break;
switch (this._statementStack.Peek())
{
case ForStatement:
case AssignStatement assign when string.Equals(id.Identifier, assign.Identifier, StringComparison.OrdinalIgnoreCase):
isValid = false;
break;
}
}

base.DefaultVisit(node);
if (isValid)
{
this._variables.Add(id.Identifier);
return base.VisitMemberExpression(memberExpression);
}
}

// Found something unsupported. Bail.
this._valid = false;
return memberExpression;
}
}
}
2 changes: 1 addition & 1 deletion dotnet/src/Extensions/PromptTemplates.Liquid/PromptTemplates.Liquid.csproj
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,6 @@

<ItemGroup>
<ProjectReference Include="..\..\SemanticKernel.Core\SemanticKernel.Core.csproj" />
<PackageReference Include="Scriban" />
<PackageReference Include="Fluid.Core" />
</ItemGroup>
</Project>

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