better fix for code block with definition list #326

The bug was not in parsing code blocks but in parsing definition lists
that had code block start marker in previous line. In this case it
wouldn't consume the input, leading to infinite loop

parser/block.go

@@ -950,7 +950,7 @@ func (p *Parser) fencedCodeBlock(data []byte, doRender bool) int {
 	work.WriteString(syntax)
 	work.WriteByte('\n')
 
-	for beg < len(data) {
+	for {
 		// check for the end of the code block
 		fenceEnd, _ := isFenceLine(data[beg:], nil, marker)
 		if fenceEnd != 0 {
@@ -963,7 +963,7 @@ func (p *Parser) fencedCodeBlock(data []byte, doRender bool) int {
 
 		// did we reach the end of the buffer without a closing marker?
 		if end >= len(data) {
-			end = len(data)
+			return 0
 		}
 
 		// verbatim copy to the working buffer
@@ -1350,6 +1350,7 @@ func finalizeList(list *ast.List) {
 // Parse a single list item.
 // Assumes initial prefix is already removed if this is a sublist.
 func (p *Parser) listItem(data []byte, flags *ast.ListType) int {
+	isDefinitionList := *flags&ast.ListTypeDefinition != 0
 	// keep track of the indentation of the first line
 	itemIndent := 0
 	if data[0] == '\t' {
@@ -1382,7 +1383,7 @@ func (p *Parser) listItem(data []byte, flags *ast.ListType) int {
 	}
 	if i == 0 {
 		// if in definition list, set term flag and continue
-		if *flags&ast.ListTypeDefinition != 0 {
+		if isDefinitionList {
 			*flags |= ast.ListTypeTerm
 		} else {
 			return 0
@@ -1443,7 +1444,14 @@ gatherlines:
 
 		// If there is a fence line (marking starting of a code block)
 		// without indent do not process it as part of the list.
-		if p.extensions&FencedCode != 0 {
+		//
+		// does not apply for definition lists because it causes infinite
+		// loop if text before defintion term is fenced code block start
+		// marker but not part of actual fenced code block
+		// for defnition lists we're called after parsing fence code blocks
+		// so we kno this cannot be a fenced block
+		// https://github.com/gomarkdown/markdown/issues/326
+		if !isDefinitionList && p.extensions&FencedCode != 0 {
 			fenceLineEnd, _ := isFenceLine(chunk, nil, "")
 			if fenceLineEnd > 0 && indent == 0 {
 				*flags |= ast.ListItemEndOfList

parser/block_test.go

@@ -78,10 +78,11 @@ func TestRect(t *testing.T) {
 
 // https://github.com/gomarkdown/markdown/issues/326
 func TestInfiniteLoopFix(t *testing.T) {
-	input := "```\n: "
+	input := "```\n: la"
 	p := NewWithExtensions(CommonExtensions)
 	doc := p.Parse([]byte(input))
 	if doc == nil {
 		t.Errorf("Expected non-nil AST")
 	}
+	//ast.Print(os.Stdout, doc)
 }

s/run_tests.ps1

@@ -1,3 +1,4 @@
+$ErrorActionPreference = 'Stop'
 go clean -testcache
 #go test -race -v .
 #go test -race -v ./ast