Added ability to set the template filename

Adds RazorEngineCompilationOptions.TemplateFilename, which is used if not empty or whitespace. If it is it falls back to the existing Path.GetRandomFilename().

This is helpful for debugging which templates are causing errors as we can pass the error to to the user without additional information.

Author: Yazwh0

RazorEngineCore.Tests/TestTemplateFilename.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace RazorEngineCore.Tests
+{
+    [TestClass]
+    public class TestTemplateFilename
+    {
+        [TestMethod]
+        public void TestSettingTemplateFilename()
+        {
+            RazorEngine razorEngine = new RazorEngine();
+            var errorThrown = false;
+            try
+            {
+                IRazorEngineCompiledTemplate initialTemplate = razorEngine.Compile("@{ this is a syntaxerror }", 
+                    builder => { builder.Options.TemplateFilename = "templatefilenameset.txt"; });
+            }
+            catch (Exception e)
+            {
+                Assert.IsTrue(e.Message.Contains("templatefilenameset.txt"));
+                errorThrown = true;
+            }
+
+            Assert.IsTrue(errorThrown);
+        }
+    }
+}

RazorEngineCore/RazorEngine.cs

@@ -62,7 +62,7 @@ private MemoryStream CreateAndCompileToStream(string templateSource, RazorEngine
                     builder.SetNamespace(options.TemplateNamespace);
                 });
 
-            string fileName = Path.GetRandomFileName();
+            string fileName = string.IsNullOrWhiteSpace(options.TemplateFilename) ? Path.GetRandomFileName() : options.TemplateFilename;
 
             RazorSourceDocument document = RazorSourceDocument.Create(templateSource, fileName);
 

RazorEngineCore/RazorEngineCompilationOptions.cs

@@ -12,6 +12,7 @@ public class RazorEngineCompilationOptions
 
         public HashSet<MetadataReference> MetadataReferences { get; set; } = new HashSet<MetadataReference>();
         public string TemplateNamespace { get; set; } = "TemplateNamespace";
+        public string TemplateFilename { get; set; } = "";
         public string Inherits { get; set; } = "RazorEngineCore.RazorEngineTemplateBase";
 
         public HashSet<string> DefaultUsings { get; set; } = new HashSet<string>()