fix finding deepest user defined failing node

char.go

@@ -95,6 +95,12 @@ func (p *charParser) match(t rune) bool {
 
 func (p *charParser) parse(c *context) {
 	if tok, ok := c.token(); !ok || !p.match(tok) {
+		if c.offset > c.failOffset {
+			c.failOffset = c.offset
+			// println("clearing failing parser")
+			c.failingParser = nil
+		}
+
 		c.fail(c.offset)
 		return
 	}

choice.go

@@ -163,6 +163,8 @@ func (p *choiceParser) parse(c *context) {
 		return
 	}
 
+	// println("parsing choice", p.name, c.offset)
+
 	c.results.markPending(c.offset, p.id)
 	from := c.offset
 	to := c.offset
@@ -175,12 +177,6 @@ func (p *choiceParser) parse(c *context) {
 	// - if there is a failure already, it should be left alone
 	// - what if reading more means that the previous failurs don't count
 	initialFailOffset := c.failOffset
-	initialFailingParser := c.failingParser
-	c.failingParser = nil
-	var (
-		failOffset    int
-		failingParser parser
-	)
 
 	for {
 		foundMatch = false
@@ -192,13 +188,6 @@ func (p *choiceParser) parse(c *context) {
 
 			if !c.matchLast || match && c.offset <= to {
 				c.offset = from
-				if c.failOffset > failOffset {
-					failOffset = c.failOffset
-					failingParser = c.failingParser
-				}
-
-				c.failOffset = initialFailOffset
-				c.failingParser = nil
 				continue
 			}
 
@@ -206,8 +195,6 @@ func (p *choiceParser) parse(c *context) {
 			foundMatch = true
 			to = c.offset
 			c.offset = from
-			c.failOffset = initialFailOffset
-			c.failingParser = nil
 			c.results.setMatch(from, p.id, to)
 		}
 
@@ -217,34 +204,23 @@ func (p *choiceParser) parse(c *context) {
 	}
 
 	if match {
-		c.failOffset = initialFailOffset
-		c.failingParser = initialFailingParser
+		if to >= c.failOffset {
+			c.failOffset = -1
+			c.failingParser = nil
+		}
+
 		c.success(to)
 		c.results.unmarkPending(from, p.id)
 		return
 	}
 
-	if failOffset > initialFailOffset {
-		// println("recording choice failure", p.name, failOffset)
-		c.failOffset = failOffset
-		if failingParser == nil && p.commit&userDefined != 0 && p.commit&Whitespace == 0 {
-			// println("setting failing choice parser", p.nodeName(), failOffset)
+	// TODO:
+	// - what if all of it pending?
+	if c.failOffset > initialFailOffset && c.failingParser == nil {
+		if p.commitType()&userDefined != 0 && p.commitType()&Whitespace == 0 {
+			// println("recording choice failure", p.name, from, c.failOffset)
 			c.failingParser = p
-		} else {
-			c.failingParser = failingParser
 		}
-	} else if failOffset == initialFailOffset && initialFailingParser == nil {
-		// println("recording choice failure", p.name, failOffset)
-		c.failOffset = failOffset
-		if failingParser == nil && p.commit&userDefined != 0 && p.commit&Whitespace == 0 {
-			// println("setting failing choice parser", p.nodeName(), failOffset)
-			c.failingParser = p
-		} else {
-			c.failingParser = failingParser
-		}
-	} else {
-		c.failOffset = initialFailOffset
-		c.failingParser = initialFailingParser
 	}
 
 	c.results.setNoMatch(from, p.id)

context.go

@@ -21,8 +21,9 @@ type context struct {
 
 func newContext(r io.RuneReader) *context {
 	return &context{
-		reader:  r,
-		results: &results{},
+		reader:     r,
+		results:    &results{},
+		failOffset: -1,
 	}
 }
 
@@ -145,13 +146,17 @@ func (c *context) parseError(p parser) error {
 func (c *context) finalizeParse(root parser) error {
 	p := c.failingParser
 	if p == nil {
+		// println("failing parser is nil")
 		p = root
 	}
 
+	// println("failing parser is", p.nodeName())
+
 	to, match, found := c.results.longestResult(0, root.nodeID())
 
 	if found && match && to < c.readOffset {
-		return c.parseError(root)
+		// println("forcing root", found, match, to, c.readOffset)
+		return c.parseError(p)
 	}
 
 	// TODO: test both cases

errors_test.go

@@ -149,7 +149,8 @@ func TestError(t *testing.T) {
 }
 
 func TestErrorRecursive(t *testing.T) {
-	const doc = `a[b][1a]`
+	// const doc = `a[b][1a]`
+	const doc = `a[1a]`
 
 	s, err := openSyntaxFile("examples/mml.treerack")
 	if err != nil {
@@ -157,7 +158,7 @@ func TestErrorRecursive(t *testing.T) {
 		return
 	}
 
-	// println("starting")
+	// println("\n<<<< starting >>>>\n")
 	_, err = s.Parse(bytes.NewBufferString(doc))
 	perr, ok := err.(*ParseError)
 	if !ok {

sequence.go

@@ -307,13 +307,19 @@ func (p *sequenceParser) parse(c *context) {
 	from := c.offset
 	to := c.offset
 	var parsed bool
+	initialFailOffset := c.failOffset
 
 	for itemIndex < len(p.items) {
 		p.items[itemIndex].parse(c)
 		if !c.matchLast {
 			if currentCount < p.ranges[itemIndex][0] {
-				// println("recording sequence failure", p.name, c.offset)
-				c.recordFailure(c.offset, p)
+				if c.failOffset > initialFailOffset && c.failingParser == nil {
+					if p.commitType()&userDefined != 0 && p.commitType()&Whitespace == 0 {
+						// println("recording sequence failure", p.name, from, c.failOffset)
+						c.failingParser = p
+					}
+				}
+
 				c.fail(from)
 				if !p.allChars {
 					c.results.unmarkPending(from, p.id)
@@ -346,6 +352,11 @@ func (p *sequenceParser) parse(c *context) {
 		}
 	}
 
+	if to >= c.failOffset {
+		c.failOffset = -1
+		c.failingParser = nil
+	}
+
 	c.results.setMatch(from, p.id, to)
 	c.success(to)
 	if !p.allChars {