[LG] support custom function

libraries/Microsoft.Bot.Builder.LanguageGeneration/LGParser.cs

@@ -6,6 +6,7 @@
 using System.IO;
 using System.Linq;
 using System.Text.RegularExpressions;
+using AdaptiveExpressions;
 using Antlr4.Runtime;
 
 namespace Microsoft.Bot.Builder.LanguageGeneration
@@ -33,13 +34,17 @@ public static class LGParser
         /// </summary>
         /// <param name="filePath"> absolut path of a LG file.</param>
         /// <param name="importResolver">resolver to resolve LG import id to template text.</param>
+        /// <param name="expressionEngine">expressionEngine Expression engine for evaluating expressions.</param>
         /// <returns>new <see cref="LGFile"/> entity.</returns>
-        public static LGFile ParseFile(string filePath, ImportResolverDelegate importResolver = null)
+        public static LGFile ParseFile(
+            string filePath,
+            ImportResolverDelegate importResolver = null,
+            ExpressionEngine expressionEngine = null)
         {
             var fullPath = Path.GetFullPath(filePath.NormalizePath());
             var content = File.ReadAllText(fullPath);
 
-            return ParseText(content, fullPath, importResolver);
+            return ParseText(content, fullPath, importResolver, expressionEngine);
         }
 
         /// <summary>
@@ -48,11 +53,17 @@ public static LGFile ParseFile(string filePath, ImportResolverDelegate importRes
         /// <param name="content">Text content contains lg templates.</param>
         /// <param name="id">id is the identifier of content. If importResolver is null, id must be a full path string. </param>
         /// <param name="importResolver">resolver to resolve LG import id to template text.</param>
+        /// <param name="expressionEngine">expressionEngine Expression engine for evaluating expressions.</param>
         /// <returns>new <see cref="LGFile"/> entity.</returns>
-        public static LGFile ParseText(string content, string id = "", ImportResolverDelegate importResolver = null)
+        public static LGFile ParseText(
+            string content,
+            string id = "",
+            ImportResolverDelegate importResolver = null,
+            ExpressionEngine expressionEngine = null)
         {
             importResolver = importResolver ?? DefaultFileResolver;
-            var lgFile = new LGFile(content: content, id: id, importResolver: importResolver);
+            var lgFile = new LGFile(content: content, id: id, importResolver: importResolver, expressionEngine: expressionEngine);
+
             var diagnostics = new List<Diagnostic>();
             try
             {

libraries/Microsoft.Bot.Builder.LanguageGeneration/StaticChecker.cs

@@ -26,10 +26,10 @@ internal class StaticChecker : LGFileParserBaseVisitor<List<Diagnostic>>
         /// </summary>
         /// <param name="lgFile">the lgFile wihch would be checked.</param>
         /// <param name="expressionEngine">Init expression engine.</param>
-        public StaticChecker(LGFile lgFile, ExpressionEngine expressionEngine = null)
+        public StaticChecker(LGFile lgFile)
         {
             this.lgFile = lgFile;
-            baseExpressionEngine = expressionEngine ?? new ExpressionEngine();
+            baseExpressionEngine = lgFile.ExpressionEngine;
         }
 
         // Create a property because we want this to be lazy loaded

tests/Microsoft.Bot.Builder.LanguageGeneration.Tests/Examples/CustomFunction.lg

@@ -0,0 +1,2 @@
+# template
+- ${custom(1, 2)}

tests/Microsoft.Bot.Builder.LanguageGeneration.Tests/LGFileTest.cs

@@ -6,6 +6,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using AdaptiveExpressions;
 using AdaptiveExpressions.Memory;
 using Microsoft.Bot.Builder.LanguageGeneration;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
@@ -984,6 +985,25 @@ public void TestInlineEvaluate()
             Assert.IsTrue(exception.Message.Contains("it's not a built-in function or a customized function"));
         }
 
+        [TestMethod]
+        public void TestCustomFunction()
+        {
+            var engine = new ExpressionEngine((string func) =>
+            { 
+                if (func == "custom")
+                {
+                    return ExpressionFunctions.Numeric("custom", (args) => args[0] + args[1]);
+                }
+                else
+                {
+                    return ExpressionFunctions.Lookup(func);
+                }
+            });
+            var lgFile = LGParser.ParseFile(GetExampleFilePath("CustomFunction.lg"), null, engine);
+            var evaled = lgFile.EvaluateTemplate("template");
+            Assert.AreEqual(3, evaled);
+        }
+
         public class LoopClass
         {
             public string Name { get; set; }

tests/Microsoft.Bot.Builder.LanguageGeneration.Tests/Microsoft.Bot.Builder.LanguageGeneration.Tests.csproj

@@ -42,6 +42,7 @@
     <None Remove="Examples\StringInterpolation.lg" />
     <None Remove="Examples\ReExecute.lg" />
     <None Remove="Examples\NullTolerant.lg" />
+    <None Remove="Examples\CustomFunction.lg" />
     <None Remove="ExceptionExamples\ConditionFormatError.lg" />
     <None Remove="ExceptionExamples\DuplicatedTemplates.lg" />
     <None Remove="ExceptionExamples\EmptyLGFile.lg" />
@@ -160,6 +161,10 @@
     <Content Include="Examples\NullTolerant.lg">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
+    <Content Include="Examples\CustomFunction.lg">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+
     <Content Include="ExceptionExamples\ConditionFormatError.lg">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>