Fix quoteblock with setexheading when no lazy continuations are involved

src/Markdig/Parsers/BlockProcessor.cs

@@ -150,6 +150,11 @@ public BlockProcessor(MarkdownDocument document, BlockParserList parsers, Markdo
         /// Gets the character position before the indent occurred.
         /// </summary>
         public int StartBeforeIndent { get; private set; }
+
+        /// <summary>
+        /// Gets a boolean indicating whether the current line being parsed is lazy continuation.
+        /// </summary>
+        public bool IsLazy { get; private set; }
 
         /// <summary>
         /// Gets the current stack of <see cref="Block"/> being processed.
@@ -577,6 +582,8 @@ private void UpdateLastBlockAndContainer(int stackIndex = -1)
         /// </exception>
         private void TryContinueBlocks()
         {
+            IsLazy = false;
+
             // Set all blocks non opened.
             // They will be marked as open in the following loop
             for (int i = 1; i < OpenedBlocks.Count; i++)
@@ -712,6 +719,7 @@ private bool TryOpenBlocks(BlockParser[] parsers)
         {
             for (int j = 0; j < parsers.Length; j++)
             {
+                IsLazy = false;
                 var blockParser = parsers[j];
                 if (Line.IsEmpty)
                 {
@@ -731,17 +739,17 @@ private bool TryOpenBlocks(BlockParser[] parsers)
                     continue;
                 }
 
-                bool isLazyParagraph = blockParser is ParagraphBlockParser && lastBlock is ParagraphBlock;
+                IsLazy = blockParser is ParagraphBlockParser && lastBlock is ParagraphBlock;
 
-                var result = isLazyParagraph
+                var result = IsLazy
                     ? blockParser.TryContinue(this, lastBlock)
                     : blockParser.TryOpen(this);
 
                 if (result == BlockState.None)
                 {
                     // If we have reached a blank line after trying to parse a paragraph
                     // we can ignore it
-                    if (isLazyParagraph && IsBlankLine)
+                    if (IsLazy && IsBlankLine)
                     {
                         ContinueProcessingLine = false;
                         break;
@@ -752,7 +760,7 @@ private bool TryOpenBlocks(BlockParser[] parsers)
                 // Special case for paragraph
                 UpdateLastBlockAndContainer();
 
-                if (isLazyParagraph && CurrentBlock is ParagraphBlock paragraph)
+                if (IsLazy && CurrentBlock is ParagraphBlock paragraph)
                 {
                     Debug.Assert(NewBlocks.Count == 0);
 
@@ -782,6 +790,8 @@ private bool TryOpenBlocks(BlockParser[] parsers)
 
                 // We have a leaf node, we can stop
             }
+
+            IsLazy = false;
             return false;
         }
 

src/Markdig/Parsers/ParagraphBlockParser.cs

@@ -38,7 +38,7 @@ public override BlockState TryContinue(BlockProcessor processor, Block block)
                 return BlockState.BreakDiscard;
             }
 
-            if (ParseSetexHeadings && !processor.IsCodeIndent)
+            if (!processor.IsCodeIndent && ParseSetexHeadings)
             {
                 return TryParseSetexHeading(processor, block);
             }
@@ -86,7 +86,11 @@ private BlockState TryParseSetexHeading(BlockProcessor state, Block block)
 
                 // If we matched a LinkReferenceDefinition before matching the heading, and the remaining
                 // lines are empty, we can early exit and remove the paragraph
-                if (!(TryMatchLinkReferenceDefinition(ref paragraph.Lines, state) && paragraph.Lines.Count == 0))
+                var parent = block.Parent;
+
+                bool isSetTextHeading = !state.IsLazy || paragraph.Column == state.Column || !(parent is QuoteBlock || parent is ListItemBlock);
+
+                if (!(TryMatchLinkReferenceDefinition(ref paragraph.Lines, state) && paragraph.Lines.Count == 0) && isSetTextHeading)
                 {
                     // We discard the paragraph that will be transformed to a heading
                     state.Discard(paragraph);

src/Markdig/Parsers/ThematicBreakParser.cs

@@ -74,7 +74,7 @@ public override BlockState TryOpen(BlockProcessor processor)
             if (isSetexHeading)
             {
                 var parent = previousParagraph.Parent;
-                if ((parent is QuoteBlock && processor.CurrentLineStartPosition > parent.Span.End) || (parent is ListItemBlock && previousParagraph.Column != processor.Column))
+                if (previousParagraph.Column != processor.Column && (parent is QuoteBlock || parent is ListItemBlock))
                 {
                     isSetexHeading = false;
                 }