Fixed a error, that occurred during the generation of error message

Author: Taritsyn

src/MsieJavaScriptEngine/ActiveScript/ActiveScriptJsEngineBase.ScriptSiteBase.cs

@@ -130,7 +130,7 @@ protected ActiveScriptException CreateActiveScriptException(IActiveScriptError e
 						string sourceLine;
 						error.GetSourceLineText(out sourceLine);
 
-						sourceFragment = JsErrorHelpers.GetSourceFragment(sourceLine, columnNumber);
+						sourceFragment = JsErrorHelpers.GetSourceFragmentFromLine(sourceLine, columnNumber);
 					}
 					else
 					{

src/MsieJavaScriptEngine/Helpers/JsErrorHelpers.cs

@@ -461,7 +461,7 @@ public static JsEngineLoadException WrapEngineLoadException(Exception exception,
 		/// <param name="sourceLine">Content of the source line</param>
 		/// <param name="columnNumber">Column number</param>
 		/// <param name="maxFragmentLength">Maximum length of the source fragment</param>
-		internal static string GetSourceFragment(string sourceLine, int columnNumber,
+		public static string GetSourceFragmentFromLine(string sourceLine, int columnNumber,
 			int maxFragmentLength = 100)
 		{
 			if (string.IsNullOrEmpty(sourceLine))
@@ -480,7 +480,14 @@ internal static string GetSourceFragment(string sourceLine, int columnNumber,
 
 				var leftOffset = (int)Math.Floor((double)maxFragmentLength / 2);
 				int fragmentStartPosition = columnNumber - leftOffset - 1;
-				if (fragmentStartPosition < 0)
+				if (fragmentStartPosition > 0)
+				{
+					if (lineLength - fragmentStartPosition < maxFragmentLength)
+					{
+						fragmentStartPosition = lineLength - maxFragmentLength;
+					}
+				}
+				else
 				{
 					fragmentStartPosition = 0;
 				}
@@ -489,12 +496,10 @@ internal static string GetSourceFragment(string sourceLine, int columnNumber,
 				if (fragmentStartPosition > 0)
 				{
 					startPart = ellipsisSymbol;
-					fragmentLength--;
 				}
-				if (fragmentStartPosition + maxFragmentLength < lineLength)
+				if (fragmentStartPosition + fragmentLength < lineLength)
 				{
 					endPart = ellipsisSymbol;
-					fragmentLength--;
 				}
 
 				StringBuilder fragmentBuilder = StringBuilderPool.GetBuilder();

src/MsieJavaScriptEngine/JsRt/Edge/ChakraEdgeJsRtJsEngine.cs

@@ -951,7 +951,7 @@ private WrapperException WrapJsException(OriginalException originalException,
 								sourceLine = sourcePropertyValue.ConvertToString().ToString();
 							}
 
-							sourceFragment = JsErrorHelpers.GetSourceFragment(sourceLine, columnNumber);
+							sourceFragment = JsErrorHelpers.GetSourceFragmentFromLine(sourceLine, columnNumber);
 							message = JsErrorHelpers.GenerateScriptErrorMessage(type, description, documentName,
 								lineNumber, columnNumber, sourceFragment);
 						}

src/MsieJavaScriptEngine/JsRt/Ie/ChakraIeJsRtJsEngine.cs

@@ -978,7 +978,7 @@ private WrapperException WrapJsException(OriginalException originalException,
 								sourceLine = sourcePropertyValue.ConvertToString().ToString();
 							}
 
-							sourceFragment = JsErrorHelpers.GetSourceFragment(sourceLine, columnNumber);
+							sourceFragment = JsErrorHelpers.GetSourceFragmentFromLine(sourceLine, columnNumber);
 							message = JsErrorHelpers.GenerateScriptErrorMessage(type, description, documentName,
 								lineNumber, columnNumber, sourceFragment);
 						}

src/MsieJavaScriptEngine/MsieJavaScriptEngine.csproj

@@ -24,7 +24,7 @@
 		<RepositoryUrl>https://github.com/Taritsyn/MsieJavaScriptEngine</RepositoryUrl>
 		<RepositoryType>git</RepositoryType>
 		<PackageTags>JavaScript;ECMAScript;MSIE;IE;Edge;Chakra</PackageTags>
-		<PackageReleaseNotes>Changed a implementation of the `Dispose` method.</PackageReleaseNotes>
+		<PackageReleaseNotes>Fixed a error, that occurred during the generation of error message.</PackageReleaseNotes>
 		<NeutralLanguage>en-US</NeutralLanguage>
 		<PackageOutputPath>../../nuget</PackageOutputPath>
 		<GeneratePackageOnBuild>true</GeneratePackageOnBuild>

src/MsieJavaScriptEngine/readme.txt

@@ -21,7 +21,7 @@
    =============
    RELEASE NOTES
    =============
-   Changed a implementation of the `Dispose` method.
+   Fixed a error, that occurred during the generation of error message.
 
    ============
    PROJECT SITE

test/MsieJavaScriptEngine.Test.Common/ErrorFormattingTests.cs

@@ -0,0 +1,75 @@
+using NUnit.Framework;
+
+using MsieJavaScriptEngine.Helpers;
+
+namespace MsieJavaScriptEngine.Test.Common
+{
+	[TestFixture]
+	public class ErrorFormattingTests
+	{
+		[Test]
+		public void GettingSourceFragmentFromLineIsCorrect()
+		{
+			// Arrange
+			const string input1 = "";
+			const string targetOutput1 = input1;
+
+			const string input2 = "	    \n";
+			const string targetOutput2 = input2;
+
+			const string input3 = "var @variable3 = 678;";
+			const string targetOutput3 = input3;
+
+			const string input4 = "	Math.hasOwnProperty(\"log2\")||(Math.log2=function(n){" +
+				"return Math.log(@n)*Math.LOG2E});";
+			const string targetOutput4 = "…Math.hasOwnProperty(\"log2\")||(Math.log2=function(n){" +
+				"return Math.log(@n)*Math.LOG2E});";
+
+			const string input5 = "function mix(destination,source){var propertyName;destination=destination||{};" +
+				"for(propertyName in source){if(source.hasOwnProperty(propertyName){" +
+				"destination[propertyName]=source[propertyName]}}return destination}"
+				;
+			const string targetOutput5 = "… in source){if(source.hasOwnProperty(propertyName){" +
+				"destination[propertyName]=source[propertyName]}}r…";
+
+			const string input6 = "Object.hasOwnProperty(\"assign)||(Object.assign=function(n){" +
+				"var u,i,f,t,r;if(typeof n==\"undefined\"||n===null)" +
+				"throw new TypeError(\"Object.assign: argument is not an Object.\");" +
+				"for(u=Object(n),f=arguments.length,i=1;i<f;i++)" +
+				"if(t=arguments[i],typeof t!=\"undefined\"&&t!==null)for(r in t)" +
+				"Object.prototype.hasOwnProperty.call(t,r)&&(u[r]=t[r]);return u});"
+				;
+			const string targetOutput6 = "Object.hasOwnProperty(\"assign)||(Object.assign=function(n){" +
+				"var u,i,f,t,r;if(typeof n==\"undefined\"||n…";
+
+			const string input7 = "function base64_encode(a){" +
+				"var b=\"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=\";" +
+				"var c,o2,o3,h1,h2,h3,h4,bits,i=0,enc='';do{c=a.charCodeAt(i++);o2=a.charCodeAt(i++);" +
+				"o3=a.charCodeAt(i++);bits=c<<16|o2<<8|o3;h1=bits>>18&0x3f;h2=bits>>12&0x3f;" +
+				"h3=bits>>6&0x3f;h4=bits&0x3f;enc+=b.charAt(h1)+b.charAt(h2)+b.charAt(h3)+b.charAt(h4)}" +
+				"while(i<a.length);switch(a.length%3){case 1:enc=enc.slice(0,-2)+'==';break;" +
+				"case 2:enc=enc.slice(0,-1)+'=';break}return @enc}"
+				;
+			const string targetOutput7 = "…(a.length%3){case 1:enc=enc.slice(0,-2)+'==';break;" +
+				"case 2:enc=enc.slice(0,-1)+'=';break}return @enc}";
+
+			// Act
+			string output1 = JsErrorHelpers.GetSourceFragmentFromLine(input1, 1, 100);
+			string output2 = JsErrorHelpers.GetSourceFragmentFromLine(input2, 1, 100);
+			string output3 = JsErrorHelpers.GetSourceFragmentFromLine(input3, 5, 100);
+			string output4 = JsErrorHelpers.GetSourceFragmentFromLine(input4, 70, 85);
+			string output5 = JsErrorHelpers.GetSourceFragmentFromLine(input5, 145, 100);
+			string output6 = JsErrorHelpers.GetSourceFragmentFromLine(input6, 23, 100);
+			string output7 = JsErrorHelpers.GetSourceFragmentFromLine(input7, 465, 100);
+
+			// Assert
+			Assert.AreEqual(targetOutput1, output1);
+			Assert.AreEqual(targetOutput2, output2);
+			Assert.AreEqual(targetOutput3, output3);
+			Assert.AreEqual(targetOutput4, output4);
+			Assert.AreEqual(targetOutput5, output5);
+			Assert.AreEqual(targetOutput6, output6);
+			Assert.AreEqual(targetOutput7, output7);
+		}
+	}
+}