Fix regression when parsing link reference definitions (#543)

Author: xoofx

src/Markdig.Tests/TestPlayParser.cs

@@ -12,6 +12,16 @@ namespace Markdig.Tests
     [TestFixture]
     public class TestPlayParser
     {
+        [Test]
+        public void TestLinksWithCarriageReturn()
+        {
+            {
+                var text = "[Link 1][link-1], [link 2][link-2].\r\n\r\n[link-1]: https://example.com\r\n[link-2]: https://example.com";
+                var result = Markdown.ToHtml(text).TrimEnd();
+                Assert.AreEqual("<p><a href=\"https://example.com\">Link 1</a>, <a href=\"https://example.com\">link 2</a>.</p>", result);
+            }
+        }
+
         [Test]
         public void TestLink()
         {

src/Markdig.Tests/TestRoundtrip.cs

@@ -23,7 +23,8 @@ internal static void RoundTrip(string markdown)
 
             nr.Write(markdownDocument);
 
-            Assert.AreEqual(markdown, sw.ToString());
+            var result = sw.ToString();
+            Assert.AreEqual(markdown, result);
         }
     }
 }

src/Markdig/Helpers/LinkHelper.cs

@@ -1231,7 +1231,9 @@ public static bool TryParseLinkReferenceDefinitionTrivia<T>(
             var saved = text;
             var hasWhiteSpaces = CharIteratorHelper.TrimStartAndCountNewLines(ref text, out int newLineCount, out newLine);
 
-            triviaBeforeTitle = new SourceSpan(triviaBeforeTitleStart, text.Start - 1);
+            // Remove the newline from the trivia (as it may have multiple lines)
+            var triviaBeforeTitleEnd = text.Start - 1;
+            triviaBeforeTitle = new SourceSpan(triviaBeforeTitleStart, triviaBeforeTitleEnd);
             var c = text.CurrentChar;
             if (c == '\'' || c == '"' || c == '(')
             {
@@ -1246,6 +1248,9 @@ public static bool TryParseLinkReferenceDefinitionTrivia<T>(
                     {
                         return false;
                     }
+
+                    // Discard the newline if we have a title
+                    newLine = NewLine.None;
                 }
                 else
                 {
@@ -1256,6 +1261,8 @@ public static bool TryParseLinkReferenceDefinitionTrivia<T>(
             {
                 if (text.IsEmpty || newLineCount > 0)
                 {
+                    // If we have an end of line, we need to remove it from the trivia
+                    triviaBeforeTitle.End -= newLine.Length();
                     triviaAfterTitle = new SourceSpan(text.Start, text.Start - 1);
                     return true;
                 }
@@ -1277,6 +1284,7 @@ public static bool TryParseLinkReferenceDefinitionTrivia<T>(
                 {
                     text = saved;
                     title = null;
+                    newLine = NewLine.None;
                     unescapedTitle = SourceSpan.Empty;
                     triviaAfterTitle = SourceSpan.Empty;
                     return true;

src/Markdig/Helpers/StringLineGroup.cs

@@ -299,7 +299,7 @@ public char NextChar()
                                 CurrentChar = '\r';
                             }
                         }
-                        else if (_offset + 1 == slice.Length)
+                        else if (_offset - 1 == slice.Length)
                         {
                             if (newLine == NewLine.CarriageReturnLineFeed)
                             {

src/Markdig/Syntax/CharIteratorHelper.cs

@@ -13,45 +13,39 @@ public static class CharIteratorHelper
     {
         public static bool TrimStartAndCountNewLines<T>(ref T iterator, out int countNewLines) where T : ICharIterator
         {
-            countNewLines = 0;
-            var c = iterator.CurrentChar;
-            bool hasWhitespaces = false;
-            while (c.IsWhitespace())
-            {
-                if (c == '\n')
-                {
-                    countNewLines++;
-                }
-                hasWhitespaces = true;
-                c = iterator.NextChar();
-            }
-            return hasWhitespaces;
+            return TrimStartAndCountNewLines(ref iterator, out countNewLines, out _);
         }
 
-        public static bool TrimStartAndCountNewLines<T>(ref T iterator, out int countNewLines, out NewLine firstNewline) where T : ICharIterator
+        public static bool TrimStartAndCountNewLines<T>(ref T iterator, out int countNewLines, out NewLine lastLine) where T : ICharIterator
         {
             countNewLines = 0;
             var c = iterator.CurrentChar;
             bool hasWhitespaces = false;
-            firstNewline = NewLine.None;
-            while (c.IsWhitespace())
+            lastLine = NewLine.None;
+            while (c != '\0' && c.IsWhitespace())
             {
                 if (c == '\n' || c == '\r')
                 {
-                    if (c == '\r' && iterator.PeekChar() == '\n' && firstNewline != NewLine.None)
+                    if (c == '\r' && iterator.PeekChar() == '\n')
                     {
-                        firstNewline = NewLine.CarriageReturnLineFeed;
+                        lastLine = NewLine.CarriageReturnLineFeed;
+                        iterator.SkipChar(); // skip \n
                     }
-                    else if (c == '\n' && firstNewline != NewLine.None)
+                    else if (c == '\n')
                     {
-                        firstNewline = NewLine.LineFeed;
+                        lastLine = NewLine.LineFeed;
                     }
-                    else if (c == '\r' && firstNewline != NewLine.None)
+                    else if (c == '\r')
                     {
-                        firstNewline = NewLine.CarriageReturn;
+                        lastLine = NewLine.CarriageReturn;
                     }
                     countNewLines++;
                 }
+                else
+                {
+                    // reset last line if if have a whitespace after
+                    lastLine = NewLine.None;
+                }
                 hasWhitespaces = true;
                 c = iterator.NextChar();
             }