Add TextScanner tests

* Fix off-by-one error in error location reported by TextScanner.Assert
* Fix error handling for invalid comments

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test/LightJson/Serialization/TextScannerTests.cs

@@ -0,0 +1,52 @@
+// Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
+// Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
+
+namespace StyleCop.Analyzers.Test.LightJson.Serialization
+{
+    using global::LightJson;
+    using global::LightJson.Serialization;
+    using Xunit;
+
+    public class TextScannerTests
+    {
+        [Fact]
+        public void TestUnexpectedLookahead()
+        {
+            JsonParseException ex;
+
+            ex = Assert.ThrowsAny<JsonParseException>(() => JsonValue.Parse("trUe"));
+            Assert.Equal(JsonParseException.ErrorType.InvalidOrUnexpectedCharacter, ex.Type);
+            Assert.Equal(0, ex.Position.Line);
+            Assert.Equal(2, ex.Position.Column);
+
+            ex = Assert.ThrowsAny<JsonParseException>(() => JsonValue.Parse("tr"));
+            Assert.Equal(JsonParseException.ErrorType.IncompleteMessage, ex.Type);
+            Assert.Equal(0, ex.Position.Line);
+            Assert.Equal(2, ex.Position.Column);
+        }
+
+        [Fact]
+        public void TestIncompleteComment()
+        {
+            var ex = Assert.ThrowsAny<JsonParseException>(() => JsonValue.Parse("{ /1 }"));
+            Assert.Equal(JsonParseException.ErrorType.InvalidOrUnexpectedCharacter, ex.Type);
+            Assert.Contains("'1'", ex.Message);
+            Assert.Equal(0, ex.Position.Line);
+            Assert.Equal(3, ex.Position.Column);
+
+            ex = Assert.ThrowsAny<JsonParseException>(() => JsonValue.Parse("{ // ignored text }"));
+            Assert.Equal(JsonParseException.ErrorType.IncompleteMessage, ex.Type);
+
+            ex = Assert.ThrowsAny<JsonParseException>(() => JsonValue.Parse("{ /* ignored text }"));
+            Assert.Equal(JsonParseException.ErrorType.IncompleteMessage, ex.Type);
+        }
+
+        [Fact]
+        public void TestBlockCommentTermination()
+        {
+            var obj = JsonValue.Parse("{ /* * / */ }");
+            Assert.Equal(JsonValueType.Object, obj.Type);
+            Assert.Equal(0, obj.AsJsonObject.Count);
+        }
+    }
+}

StyleCop.Analyzers/StyleCop.Analyzers.Test/StyleCop.Analyzers.Test.csproj

@@ -239,6 +239,7 @@
     <Compile Include="LightJson\JsonObjectTests.cs" />
     <Compile Include="LightJson\JsonReaderTests.cs" />
     <Compile Include="LightJson\JsonValueTests.cs" />
+    <Compile Include="LightJson\Serialization\TextScannerTests.cs" />
     <Compile Include="Lightup\AccessorDeclarationSyntaxExtensionsTests.cs" />
     <Compile Include="Lightup\AutoWrapSeparatedSyntaxListTests.cs" />
     <Compile Include="Lightup\BaseMethodDeclarationSyntaxExtensionsTests.cs" />

StyleCop.Analyzers/StyleCop.Analyzers/LightJson/Serialization/TextScanner.cs

@@ -110,7 +110,7 @@ public void SkipWhitespace()
                 }
                 else if (next == '/')
                 {
-                    this.SkipCommentOrInvalidSlash();
+                    this.SkipComment();
                     continue;
                 }
                 else
@@ -127,12 +127,13 @@ public void SkipWhitespace()
         /// <param name="next">The expected character.</param>
         public void Assert(char next)
         {
+            var errorPosition = this.position;
             if (this.Read() != next)
             {
                 throw new JsonParseException(
                     string.Format("Parser expected '{0}'", next),
                     ErrorType.InvalidOrUnexpectedCharacter,
-                    this.position);
+                    errorPosition);
             }
         }
 
@@ -149,9 +150,9 @@ public void Assert(string next)
             }
         }
 
-        private void SkipCommentOrInvalidSlash()
+        private void SkipComment()
         {
-            // First character is the a slash
+            // First character is the first slash
             this.Read();
             switch (this.Peek())
             {
@@ -164,7 +165,10 @@ private void SkipCommentOrInvalidSlash()
                 return;
 
             default:
-                return;
+                throw new JsonParseException(
+                    string.Format("Parser expected '{0}'", this.Peek()),
+                    ErrorType.InvalidOrUnexpectedCharacter,
+                    this.position);
             }
         }