Add line pragmas to dynamic attributes.

- This enables debugging and proper error reporting for dynamic attributes. Without the pragmas errors would showcase generated Razor C# instead of their corresponding .cshtml files.
- Did not have to do any `TagHelper` specific changes since they utilize the same core attribute rendering logic.
- Updated generated C# files for tests.

#569

src/Microsoft.AspNet.Razor/CodeGenerators/Visitors/CSharpCodeVisitor.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Diagnostics;
 using System.Globalization;
 using System.Linq;
 using Microsoft.AspNet.Razor.Chunks;
@@ -181,6 +182,17 @@ namespace Microsoft.AspNet.Razor.CodeGenerators.Visitors
             var currentRenderingMode = Context.ExpressionRenderingMode;
             var currentTargetWriterName = Context.TargetWriterName;
 
+            CSharpLineMappingWriter lineMappingWriter = null;
+            var code = chunk.Children.FirstOrDefault();
+            if (code is ExpressionChunk || code is ExpressionBlockChunk)
+            {
+                // We only want to render the #line pragma if the attribute value will be in-lined.
+                // Ex: WriteAttributeValue("", 0, DateTime.Now, 0, 0, false)
+                // For non-inlined scenarios: WriteAttributeValue("", 0, (_) => ..., 0, 0, false)
+                // the line pragma will be generated inside the lambda.
+                lineMappingWriter = new CSharpLineMappingWriter(Writer, chunk.Start, Context.SourceFile);
+            }
+
             if (!string.IsNullOrEmpty(currentTargetWriterName))
             {
                 Writer.WriteStartMethodInvocation(Context.Host.GeneratedClassContext.WriteAttributeValueToMethodName)
@@ -194,9 +206,10 @@ namespace Microsoft.AspNet.Razor.CodeGenerators.Visitors
 
             Context.TargetWriterName = ValueWriterName;
 
-            var code = chunk.Children.FirstOrDefault();
             if (code is ExpressionChunk || code is ExpressionBlockChunk)
             {
+                Debug.Assert(lineMappingWriter != null);
+
                 Writer
                     .WriteLocationTaggedString(chunk.Prefix)
                     .WriteParameterSeparator();
@@ -213,6 +226,8 @@ namespace Microsoft.AspNet.Razor.CodeGenerators.Visitors
                     .WriteParameterSeparator()
                     .WriteBooleanLiteral(value: false)
                     .WriteEndMethodInvocation();
+
+                lineMappingWriter.Dispose();
             }
             else
             {

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/ComplexTagHelpers.cs

@@ -242,7 +242,11 @@ if(true) {
             BeginAddHtmlAttributeValues(__tagHelperExecutionContext, "time", 3);
             AddHtmlAttributeValue("", 148, "Current", 148, 7, true);
             AddHtmlAttributeValue(" ", 155, "Time:", 156, 6, true);
-            AddHtmlAttributeValue(" ", 161, DateTime.Now, 162, 14, false);
+#line 8 "ComplexTagHelpers.cshtml"
+AddHtmlAttributeValue(" ", 161, DateTime.Now, 162, 14, false);
+
+#line default
+#line hidden
             EndAddHtmlAttributeValues(__tagHelperExecutionContext);
             __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
             Instrumentation.BeginContext(139, 529, false);

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/ConditionalAttributes.cs

@@ -26,34 +26,54 @@ namespace TestOutput
             WriteLiteral("    <a href=\"Foo\" />\r\n    <p");
             Instrumentation.EndContext();
             BeginWriteAttribute("class", " class=\"", 74, "\"", 86, 1);
-            WriteAttributeValue("", 82, cls, 82, 4, false);
+#line 5 "ConditionalAttributes.cshtml"
+WriteAttributeValue("", 82, cls, 82, 4, false);
+
+#line default
+#line hidden
             EndWriteAttribute();
             Instrumentation.BeginContext(87, 11, true);
             WriteLiteral(" />\r\n    <p");
             Instrumentation.EndContext();
             BeginWriteAttribute("class", " class=\"", 98, "\"", 114, 2);
             WriteAttributeValue("", 106, "foo", 106, 3, true);
-            WriteAttributeValue(" ", 109, cls, 110, 5, false);
+#line 6 "ConditionalAttributes.cshtml"
+WriteAttributeValue(" ", 109, cls, 110, 5, false);
+
+#line default
+#line hidden
             EndWriteAttribute();
             Instrumentation.BeginContext(115, 11, true);
             WriteLiteral(" />\r\n    <p");
             Instrumentation.EndContext();
             BeginWriteAttribute("class", " class=\"", 126, "\"", 142, 2);
-            WriteAttributeValue("", 134, cls, 134, 4, false);
+#line 7 "ConditionalAttributes.cshtml"
+WriteAttributeValue("", 134, cls, 134, 4, false);
+
+#line default
+#line hidden
             WriteAttributeValue(" ", 138, "foo", 139, 4, true);
             EndWriteAttribute();
             Instrumentation.BeginContext(143, 31, true);
             WriteLiteral(" />\r\n    <input type=\"checkbox\"");
             Instrumentation.EndContext();
             BeginWriteAttribute("checked", " checked=\"", 174, "\"", 187, 1);
-            WriteAttributeValue("", 184, ch, 184, 3, false);
+#line 8 "ConditionalAttributes.cshtml"
+WriteAttributeValue("", 184, ch, 184, 3, false);
+
+#line default
+#line hidden
             EndWriteAttribute();
             Instrumentation.BeginContext(188, 31, true);
             WriteLiteral(" />\r\n    <input type=\"checkbox\"");
             Instrumentation.EndContext();
             BeginWriteAttribute("checked", " checked=\"", 219, "\"", 236, 2);
             WriteAttributeValue("", 229, "foo", 229, 3, true);
-            WriteAttributeValue(" ", 232, ch, 233, 4, false);
+#line 9 "ConditionalAttributes.cshtml"
+WriteAttributeValue(" ", 232, ch, 233, 4, false);
+
+#line default
+#line hidden
             EndWriteAttribute();
             Instrumentation.BeginContext(237, 11, true);
             WriteLiteral(" />\r\n    <p");
@@ -86,13 +106,21 @@ WriteTo(__razor_attribute_value_writer, cls);
             WriteLiteral(" />\r\n    <a href=\"~/Foo\" />\r\n    <script");
             Instrumentation.EndContext();
             BeginWriteAttribute("src", " src=\"", 322, "\"", 373, 1);
-            WriteAttributeValue("", 328, Url.Content("~/Scripts/jquery-1.6.2.min.js"), 328, 45, false);
+#line 12 "ConditionalAttributes.cshtml"
+WriteAttributeValue("", 328, Url.Content("~/Scripts/jquery-1.6.2.min.js"), 328, 45, false);
+
+#line default
+#line hidden
             EndWriteAttribute();
             Instrumentation.BeginContext(374, 46, true);
             WriteLiteral(" type=\"text/javascript\"></script>\r\n    <script");
             Instrumentation.EndContext();
             BeginWriteAttribute("src", " src=\"", 420, "\"", 487, 1);
-            WriteAttributeValue("", 426, Url.Content("~/Scripts/modernizr-2.0.6-development-only.js"), 426, 61, false);
+#line 13 "ConditionalAttributes.cshtml"
+WriteAttributeValue("", 426, Url.Content("~/Scripts/modernizr-2.0.6-development-only.js"), 426, 61, false);
+
+#line default
+#line hidden
             EndWriteAttribute();
             Instrumentation.BeginContext(488, 152, true);
             WriteLiteral(" type=\"text/javascript\"></script>\r\n    <script src=\"http://ajax.aspnetcdn.com/aja" +

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/DynamicAttributeTagHelpers.cs

@@ -34,7 +34,11 @@ namespace TestOutput
             __tagHelperExecutionContext.Add(__InputTagHelper);
             BeginAddHtmlAttributeValues(__tagHelperExecutionContext, "unbound", 2);
             AddHtmlAttributeValue("", 51, "prefix", 51, 6, true);
-            AddHtmlAttributeValue(" ", 57, DateTime.Now, 58, 14, false);
+#line 3 "DynamicAttributeTagHelpers.cshtml"
+AddHtmlAttributeValue(" ", 57, DateTime.Now, 58, 14, false);
+
+#line default
+#line hidden
             EndAddHtmlAttributeValues(__tagHelperExecutionContext);
             __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
             Instrumentation.BeginContext(35, 40, false);
@@ -113,7 +117,11 @@ WriteLiteral(DateTime.Now);
             __tagHelperExecutionContext.AddTagHelperAttribute("bound", __InputTagHelper.Bound);
             BeginAddHtmlAttributeValues(__tagHelperExecutionContext, "unbound", 3);
             AddHtmlAttributeValue("", 206, "prefix", 206, 6, true);
-            AddHtmlAttributeValue(" ", 212, DateTime.Now, 213, 14, false);
+#line 7 "DynamicAttributeTagHelpers.cshtml"
+AddHtmlAttributeValue(" ", 212, DateTime.Now, 213, 14, false);
+
+#line default
+#line hidden
             AddHtmlAttributeValue(" ", 226, "suffix", 227, 7, true);
             EndAddHtmlAttributeValues(__tagHelperExecutionContext);
             __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
@@ -174,7 +182,11 @@ WriteLiteral(int.MaxValue);
             __InputTagHelper.Bound = __tagHelperStringValueBuffer.GetContent(HtmlEncoder);
             __tagHelperExecutionContext.AddTagHelperAttribute("bound", __InputTagHelper.Bound);
             BeginAddHtmlAttributeValues(__tagHelperExecutionContext, "unbound", 3);
-            AddHtmlAttributeValue("", 347, long.MinValue, 347, 14, false);
+#line 10 "DynamicAttributeTagHelpers.cshtml"
+AddHtmlAttributeValue("", 347, long.MinValue, 347, 14, false);
+
+#line default
+#line hidden
             AddHtmlAttributeValue(" ", 361, new Template((__razor_attribute_value_writer) => {
 #line 10 "DynamicAttributeTagHelpers.cshtml"
 if (true) { 
@@ -210,7 +222,11 @@ WriteTo(__razor_attribute_value_writer, false);
 
             }
             ), 362, 45, false);
-            AddHtmlAttributeValue(" ", 406, int.MaxValue, 407, 14, false);
+#line 10 "DynamicAttributeTagHelpers.cshtml"
+AddHtmlAttributeValue(" ", 406, int.MaxValue, 407, 14, false);
+
+#line default
+#line hidden
             EndAddHtmlAttributeValues(__tagHelperExecutionContext);
             __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
             Instrumentation.BeginContext(241, 183, false);
@@ -226,11 +242,23 @@ WriteTo(__razor_attribute_value_writer, false);
             __InputTagHelper = CreateTagHelper<InputTagHelper>();
             __tagHelperExecutionContext.Add(__InputTagHelper);
             BeginAddHtmlAttributeValues(__tagHelperExecutionContext, "unbound", 5);
-            AddHtmlAttributeValue("", 444, long.MinValue, 444, 14, false);
+#line 12 "DynamicAttributeTagHelpers.cshtml"
-            AddHtmlAttributeValue(" ", 458, DateTime.Now, 459, 14, false);
+AddHtmlAttributeValue("", 444, long.MinValue, 444, 14, false);
+
+#line default
+#line hidden
+#line 12 "DynamicAttributeTagHelpers.cshtml"
+AddHtmlAttributeValue(" ", 458, DateTime.Now, 459, 14, false);
+
+#line default
+#line hidden
             AddHtmlAttributeValue(" ", 472, "static", 473, 7, true);
             AddHtmlAttributeValue("    ", 479, "content", 483, 11, true);
-            AddHtmlAttributeValue(" ", 490, int.MaxValue, 491, 14, false);
+#line 12 "DynamicAttributeTagHelpers.cshtml"
+AddHtmlAttributeValue(" ", 490, int.MaxValue, 491, 14, false);
+
+#line default
+#line hidden
             EndAddHtmlAttributeValues(__tagHelperExecutionContext);
             __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
             Instrumentation.BeginContext(428, 80, false);

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/TagHelpersInSection.cs

@@ -86,7 +86,11 @@ WriteLiteral(DateTime.Now);
                 BeginAddHtmlAttributeValues(__tagHelperExecutionContext, "unboundproperty", 3);
                 AddHtmlAttributeValue("", 188, "Current", 188, 7, true);
                 AddHtmlAttributeValue(" ", 195, "Time:", 196, 6, true);
-                AddHtmlAttributeValue(" ", 201, DateTime.Now, 202, 14, false);
+#line 9 "TagHelpersInSection.cshtml"
+AddHtmlAttributeValue(" ", 201, DateTime.Now, 202, 14, false);
+
+#line default
+#line hidden
                 EndAddHtmlAttributeValues(__tagHelperExecutionContext);
                 __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
                 Instrumentation.BeginContext(114, 245, false);

test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/TransitionsInTagHelperAttributes.cs

@@ -68,7 +68,11 @@ namespace TestOutput
             __PTagHelper = CreateTagHelper<PTagHelper>();
             __tagHelperExecutionContext.Add(__PTagHelper);
             BeginAddHtmlAttributeValues(__tagHelperExecutionContext, "class", 1);
-            AddHtmlAttributeValue("", 155, @class, 155, 9, false);
+#line 8 "TransitionsInTagHelperAttributes.cshtml"
+AddHtmlAttributeValue("", 155, @class, 155, 9, false);
+
+#line default
+#line hidden
             EndAddHtmlAttributeValues(__tagHelperExecutionContext);
 #line 8 "TransitionsInTagHelperAttributes.cshtml"
        __PTagHelper.Age = 42;
@@ -151,7 +155,11 @@ namespace TestOutput
             __tagHelperExecutionContext.Add(__PTagHelper);
             BeginAddHtmlAttributeValues(__tagHelperExecutionContext, "class", 2);
             AddHtmlAttributeValue("", 298, "custom-", 298, 7, true);
-            AddHtmlAttributeValue("", 305, @class, 305, 9, false);
+#line 12 "TransitionsInTagHelperAttributes.cshtml"
+AddHtmlAttributeValue("", 305, @class, 305, 9, false);
+
+#line default
+#line hidden
             EndAddHtmlAttributeValues(__tagHelperExecutionContext);
 #line 12 "TransitionsInTagHelperAttributes.cshtml"
               __PTagHelper.Age = 4 * @(@int + 2);