fix choice error reporting

char.go

@@ -58,7 +58,7 @@ func (p *charParser) match(t rune) bool {
 
 func (p *charParser) parse(c *context) {
 	if tok, ok := c.token(); !ok || !p.match(tok) {
-		c.fail(p, c.offset)
+		c.fail(c.offset)
 		return
 	}
 

choice.go

@@ -141,7 +141,7 @@ func (p *choiceParser) parse(c *context) {
 	}
 
 	if c.results.pending(c.offset, p.id) {
-		c.fail(p, c.offset)
+		c.fail(c.offset)
 		return
 	}
 
@@ -186,7 +186,8 @@ func (p *choiceParser) parse(c *context) {
 	}
 
 	c.results.setNoMatch(from, p.id)
-	c.fail(p, from)
+	c.recordFailure(p)
+	c.fail(from)
 	c.results.unmarkPending(from, p.id)
 }
 

context.go

@@ -74,7 +74,7 @@ func (c *context) fromResults(p parser) bool {
 	if m {
 		c.success(to)
 	} else {
-		c.fail(p, c.offset)
+		c.fail(c.offset)
 	}
 
 	return true
@@ -88,18 +88,25 @@ func (c *context) success(to int) {
 	}
 }
 
-func (c *context) fail(p parser, offset int) {
+func (c *context) fail(offset int) {
 	c.offset = offset
 	c.matchLast = false
-	if c.failingParser == nil || c.consumed > c.failOffset {
-		// TODO: choice can be retried
-		println("setting fail", p.nodeName(), c.failingParser == nil, c.failOffset, c.consumed)
-		c.failOffset = c.consumed
+}
+
+func (c *context) recordFailure(p parser) {
+	if c.offset < c.failOffset {
+		return
+	}
+
+	if c.failingParser != nil && c.offset == c.failOffset {
+		return
+	}
+
+	c.failOffset = c.offset
 	if p.commitType()&userDefined != 0 {
 		c.failingParser = p
 	}
 }
-}
 
 func findLine(tokens []rune, offset int) (line, column int) {
 	tokens = tokens[:offset]
@@ -114,13 +121,10 @@ func findLine(tokens []rune, offset int) (line, column int) {
 	return
 }
 
-func (c *context) parseError(root parser) error {
-	definition := root.nodeName()
+func (c *context) parseError(p parser) error {
+	definition := p.nodeName()
 	if c.failingParser == nil {
-		println("setting fail", c.failOffset, c.consumed)
 		c.failOffset = c.consumed
-	} else {
-		definition = c.failingParser.nodeName()
 	}
 
 	line, col := findLine(c.tokens, c.failOffset)
@@ -134,17 +138,22 @@ func (c *context) parseError(root parser) error {
 }
 
 func (c *context) finalizeParse(root parser) error {
-	if !c.matchLast {
-		return c.parseError(root)
+	p := c.failingParser
+	if p == nil {
+		p = root
 	}
 
 	to, match, found := c.results.longestResult(0, root.nodeID())
 
-	// TODO: test all three cases
-	if !found || !match || to < c.readOffset {
+	if found && match && to < c.readOffset {
 		return c.parseError(root)
 	}
 
+	// TODO: test both cases
+	if !found || !match {
+		return c.parseError(p)
+	}
+
 	if !c.eof {
 		c.read()
 		if !c.eof {

errors_test.go

@@ -53,26 +53,26 @@ func TestError(t *testing.T) {
 		column:     2,
 		definition: "c",
 	}, {
-		title:      "choice, longer option fails",
+		title:      "choice succeeds, document fails",
 		syntax:     `a = "12"; b = "1"; c:root = a | b`,
 		text:       "13",
 		offset:     1,
 		column:     1,
-		definition: "a",
+		definition: "c",
 	}, {
-		title:      "choice, shorter option fails",
-		syntax:     `a = "2"; b = "12"; c:root = a | b`,
-		text:       "123",
-		offset:     0,
-		column:     0,
-		definition: "1",
-	}, {
-		title:      "choice, both options fail",
+		title:      "choice fails",
 		syntax:     `a = "12"; b = "2"; c:root = a | b`,
 		text:       "13",
 		offset:     1,
 		column:     1,
 		definition: "a",
+	}, {
+		title:      "choice fails, longer option reported",
+		syntax:     `a = "12"; b = "134"; c:root = a | b`,
+		text:       "135",
+		offset:     2,
+		column:     2,
+		definition: "b",
 	}} {
 		t.Run(test.title, func(t *testing.T) {
 			s, err := openSyntaxString(test.syntax)

open_test.go

@@ -17,7 +17,6 @@ func openSyntaxReader(r io.Reader) (*Syntax, error) {
 		return nil, err
 	}
 
-	println("starting")
 	s := &Syntax{}
 	if err := define(s, doc); err != nil {
 		return nil, err

sequence.go

@@ -175,7 +175,7 @@ func (p *sequenceParser) commitType() CommitType { return p.commit }
 func (p *sequenceParser) parse(c *context) {
 	if !p.allChars {
 		if c.results.pending(c.offset, p.id) {
-			c.fail(p, c.offset)
+			c.fail(c.offset)
 			return
 		}
 
@@ -192,7 +192,8 @@ func (p *sequenceParser) parse(c *context) {
 		p.items[itemIndex].parse(c)
 		if !c.matchLast {
 			if currentCount < p.ranges[itemIndex][0] {
-				c.fail(p, from)
+				c.recordFailure(p)
+				c.fail(from)
 				if !p.allChars {
 					c.results.unmarkPending(from, p.id)
 				}