Prevent RazorErrorExtensions.ToDiagnostics from throwing when it

encounters SourceLocation.Undefined \ negative error lengths

src/Microsoft.AspNet.Mvc.Razor/Precompilation/RazorErrorExtensions.cs

@@ -1,7 +1,9 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNet.Razor.Parser.SyntaxTree;
+using Microsoft.AspNet.Razor.Text;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.Framework.Internal;
@@ -20,15 +22,18 @@ namespace Microsoft.AspNet.Mvc.Razor.Precompilation
                 defaultSeverity: DiagnosticSeverity.Error,
                 isEnabledByDefault: true);
 
-            var textSpan = new TextSpan(error.Location.AbsoluteIndex, error.Length);
+            var location = error.Location;
-            var linePositionStart = new LinePosition(error.Location.LineIndex, error.Location.CharacterIndex);
+            if (location == SourceLocation.Undefined)
-            var linePositionEnd = new LinePosition(error.Location.LineIndex,
+            {
-                                                   error.Location.CharacterIndex + error.Length);
+                location = SourceLocation.Zero;
+            }
+            var length = Math.Max(0, error.Length);
+
+            var textSpan = new TextSpan(location.AbsoluteIndex, length);
+            var linePositionStart = new LinePosition(location.LineIndex, location.CharacterIndex);
+            var linePositionEnd = new LinePosition(location.LineIndex, location.CharacterIndex + length);
             var linePositionSpan = new LinePositionSpan(linePositionStart, linePositionEnd);
-
+            return Diagnostic.Create(descriptor, Location.Create(filePath, textSpan, linePositionSpan));
-            var location = Location.Create(filePath, textSpan, linePositionSpan);
-
-            return Diagnostic.Create(descriptor, location);
         }
     }
 }

test/Microsoft.AspNet.Mvc.Razor.Test/Precompilation/RazorErrorExtensionsTest.cs

@@ -0,0 +1,66 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNet.Razor.Parser.SyntaxTree;
+using Microsoft.AspNet.Razor.Text;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.Razor.Precompilation
+{
+    public class RazorErrorExtensionsTest
+    {
+        public static TheoryData ToDiagnostic_SucceedsWhenRazorErrorLocationIsZeroOrUndefinedData
+        {
+            get
+            {
+                return new TheoryData<SourceLocation, int>
+                {
+                    { SourceLocation.Undefined, -1 },
+                    { SourceLocation.Undefined, 0 },
+                    { SourceLocation.Zero, -1 },
+                    { SourceLocation.Zero, 0 },
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(ToDiagnostic_SucceedsWhenRazorErrorLocationIsZeroOrUndefinedData))]
+        public void ToDiagnostic_SucceedsWhenRazorErrorLocationIsZeroOrUndefined(
+            SourceLocation location,
+            int length)
+        {
+            // Arrange
+            var error = new RazorError("some message", location, length);
+
+            // Act
+            var diagnostics = error.ToDiagnostics("/some-path");
+
+            // Assert
+            var span = diagnostics.Location.GetMappedLineSpan();
+            Assert.Equal("/some-path", span.Path);
+            Assert.Equal(0, span.StartLinePosition.Line);
+            Assert.Equal(0, span.StartLinePosition.Character);
+            Assert.Equal(0, span.EndLinePosition.Line);
+            Assert.Equal(0, span.EndLinePosition.Character);
+        }
+
+        [Fact]
+        public void ToDiagnostic_ConvertsRazorErrorLocation_ToSourceLineMappings()
+        {
+            // Arrange
+            var sourceLocation = new SourceLocation(absoluteIndex: 30, lineIndex: 10, characterIndex: 1);
+            var error = new RazorError("some message", sourceLocation, length: 5);
+
+            // Act
+            var diagnostics = error.ToDiagnostics("/some-path");
+
+            // Assert
+            var span = diagnostics.Location.GetMappedLineSpan();
+            Assert.Equal("/some-path", span.Path);
+            Assert.Equal(10, span.StartLinePosition.Line);
+            Assert.Equal(1, span.StartLinePosition.Character);
+            Assert.Equal(10, span.EndLinePosition.Line);
+            Assert.Equal(6, span.EndLinePosition.Character);
+        }
+    }
+}