Add JSON Comment support

YamlDotNet.Test/Core/ScannerTests.cs

@@ -389,6 +389,73 @@ public void CommentsAreOmittedUnlessRequested()
                 StreamEnd);
         }
 
+        [Fact]
+        public void JsonCommentsAreReturnedWhenRequested()
+        {
+            var sut = new Scanner(Yaml.ReaderForText(@"
+                    // Top comment
+                    - first // Comment on first item
+                    - second
+                    // Bottom comment
+                "), skipComments: false);
+            sut.JsonComments = true;
+            AssertSequenceOfTokensFrom(sut,
+                StreamStart,
+                StandaloneComment("Top comment"),
+                BlockSequenceStart,
+                BlockEntry,
+                PlainScalar("first"),
+                InlineComment("Comment on first item"),
+                BlockEntry,
+                PlainScalar("second"),
+                StandaloneComment("Bottom comment"),
+                BlockEnd,
+                StreamEnd);
+        }
+
+        [Fact]
+        public void JsonCommentsAreCorrectlyMarked()
+        {
+            var sut = new Scanner(Yaml.ReaderForText(@"
+                - first // Comment on first item
+            "), skipComments: false);
+            sut.JsonComments = true;
+
+            while (sut.MoveNext())
+            {
+                if (sut.Current is Comment comment)
+                {
+                    Assert.Equal(8, comment.Start.Index);
+                    Assert.Equal(32, comment.End.Index);
+
+                    return;
+                }
+            }
+
+            Assert.Fail("Did not find a comment");
+        }
+
+        [Fact]
+        public void JsonCommentsAreOmittedUnlessRequested()
+        {
+            var sut = Yaml.ScannerForText(@"
+                    // Top comment
+                    - first // Comment on first item
+                    - second
+                    // Bottom comment
+                ");
+            sut.JsonComments = true;
+            AssertSequenceOfTokensFrom(sut,
+                StreamStart,
+                BlockSequenceStart,
+                BlockEntry,
+                PlainScalar("first"),
+                BlockEntry,
+                PlainScalar("second"),
+                BlockEnd,
+                StreamEnd);
+        }
+
         [Fact]
         public void MarksOnDoubleQuotedScalarsAreCorrect()
         {

YamlDotNet/Core/Scanner.cs

@@ -102,6 +102,11 @@ public bool SkipComments
             get; private set;
         }
 
+        public bool JsonComments
+        {
+            get; set; // Only way to set right now
+        }
+
         /// <summary>
         /// Gets the current token.
         /// </summary>
@@ -497,6 +502,7 @@ private void FetchNextToken()
             //      '-', '?', ':', ',', '[', ']', '{', '}',
             //      '#', '&', '*', '!', '|', '>', '\'', '\"',
             //      '%', '@', '`'.
+            //      Need to also block "//" when JSON Comments are enabled
 
             // In the block context (and, for the '-' indicator, in the flow context
             // too), it may also start with the characters
@@ -508,7 +514,7 @@ private void FetchNextToken()
             // The last rule is more restrictive than the specification requires.
 
 
-            var isInvalidPlainScalarCharacter = analyzer.IsWhiteBreakOrZero() || analyzer.Check("-?:,[]{}#&*!|>'\"%@`");
+            var isInvalidPlainScalarCharacter = analyzer.IsWhiteBreakOrZero() || analyzer.Check("-?:,[]{}#&*!|>'\"%@`") || CheckJsonComment();
 
             var isPlainScalar =
                 !isInvalidPlainScalarCharacter ||
@@ -560,6 +566,11 @@ private void FetchNextToken()
             throw new SyntaxErrorException(start, end, "While scanning for the next token, found character that cannot start any token.");
         }
 
+        private bool CheckJsonComment()
+        {
+            return JsonComments && analyzer.Check('/') && analyzer.Check('/', 1);
+        }
+
         private bool CheckWhiteSpace()
         {
             return analyzer.Check(' ') || ((flowLevel > 0 || !simpleKeyAllowed) && analyzer.Check('\t'));
@@ -636,13 +647,23 @@ private void ScanToNextToken()
 
         private void ProcessComment()
         {
-            if (analyzer.Check('#'))
+            // Additional check for JSON-style comments (//) to support YAML with comments in JSON style
+            // See https://github.com/aaubry/YamlDotNet/issues/1052 and https://github.com/yaml/www.yaml.org/issues/196
+            bool isYamlComment = analyzer.Check('#');
+            bool isJsonComment = !isYamlComment && CheckJsonComment();
+
+            if (isYamlComment || isJsonComment)
             {
                 var start = cursor.Mark();
 
-                // Eat '#'
+                // Eat '#' or '//'
                 Skip();
 
+                if (isJsonComment)
+                {
+                    Skip();
+                }
+
                 // Eat leading whitespace
                 while (analyzer.IsSpace())
                 {
@@ -816,11 +837,11 @@ private void FetchDirective()
             }
 
             // Eat the rest of the line including any comments.
-
-            while (analyzer.IsWhite())
-            {
-                Skip();
-            }
+            SkipWhitespaces();
+            // while (analyzer.IsWhite())
+            // {
+            //     Skip();
+            // }
 
             ProcessComment();
 
@@ -969,7 +990,7 @@ private void FetchFlowCollectionEnd(bool isSequenceToken)
             Token? token, errorToken = null;
             if (isSequenceToken)
             {
-                if (analyzer.Check('#'))
+                if (analyzer.Check('#') || CheckJsonComment())
                 {
                     errorToken = new Error("While scanning a flow sequence end, found invalid comment after ']'.", start, start);
                 }
@@ -1025,7 +1046,7 @@ private void FetchFlowEntry()
             Skip();
 
             var end = cursor.Mark();
-            if (analyzer.Check('#'))
+            if (analyzer.Check('#') || CheckJsonComment())
             {
                 tokens.Enqueue(new Error("While scanning a flow entry, found invalid comment after comma.", start, end));
                 return;
@@ -1551,17 +1572,18 @@ private Scalar ScanBlockScalar(bool isLiteral)
 
             // Check if there is a comment without whitespace after block scalar indicator (yaml-test-suite: X4QW).
 
-            if (analyzer.Check('#'))
+            if (analyzer.Check('#') || CheckJsonComment())
             {
                 throw new SyntaxErrorException(start, cursor.Mark(), "While scanning a block scalar, found a comment without whtespace after '>' indicator.");
             }
 
             // Eat whitespaces and comments to the end of the line.
 
-            while (analyzer.IsWhite())
-            {
-                Skip();
-            }
+            SkipWhitespaces();
+            // while (analyzer.IsWhite())
+            // {
+            //     Skip();
+            // }
 
             ProcessComment();
 
@@ -1787,7 +1809,7 @@ private void FetchQuotedScalar(bool isSingleQuoted)
             tokens.Enqueue(scalar);
             // Check if there is a comment subsequently after double-quoted scalar without space.
 
-            if (!isSingleQuoted && analyzer.Check('#'))
+            if (!isSingleQuoted && (analyzer.Check('#') || CheckJsonComment()))
             {
                 var start = cursor.Mark();
                 tokens.Enqueue(new Error("While scanning a flow sequence end, found invalid comment after double-quoted scalar.", start, start));
@@ -2148,7 +2170,7 @@ private Scalar ScanPlainScalar(ref bool isMultiline)
 
                 // Check for a comment.
 
-                if (analyzer.Check('#'))
+                if (analyzer.Check('#') || CheckJsonComment())
                 {
                     if (indent < 0 && flowLevel == 0)
                     {