initial error reporting

choice.go

@@ -171,6 +171,17 @@ func (p *choiceParser) parse(c *context) {
 	var optionIndex int
 	var foundMatch bool
 
+	// TODO:
+	// - 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
 		optionIndex = 0
@@ -181,6 +192,13 @@ 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
 			}
 
@@ -188,7 +206,8 @@ 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)
 		}
 
@@ -198,13 +217,37 @@ func (p *choiceParser) parse(c *context) {
 	}
 
 	if match {
+		c.failOffset = initialFailOffset
+		c.failingParser = initialFailingParser
 		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)
+			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)
-	c.recordFailure(p)
 	c.fail(from)
 	c.results.unmarkPending(from, p.id)
 }

context.go

@@ -93,17 +93,22 @@ func (c *context) fail(offset int) {
 	c.matchLast = false
 }
 
-func (c *context) recordFailure(p parser) {
+// TODO:
-	if c.offset < c.failOffset {
+// - need to know which choice branch the failure happened on because if there is a non-user branch that has the
+// longest failure, it can be reported to an unrelevant user defined choice on another branch
+
+func (c *context) recordFailure(offset int, p parser) {
+	if offset < c.failOffset {
 		return
 	}
 
-	if c.failingParser != nil && c.offset == c.failOffset {
+	if c.failingParser != nil && offset == c.failOffset {
 		return
 	}
 
-	c.failOffset = c.offset
+	c.failOffset = offset
 	if p.commitType()&userDefined != 0 && p.commitType()&Whitespace == 0 {
+		// println("setting failing sequence parser", p.nodeName(), offset)
 		c.failingParser = p
 	}
 }

errors_test.go

@@ -73,6 +73,34 @@ func TestError(t *testing.T) {
 		offset:     2,
 		column:     2,
 		definition: "b",
+	}, {
+		title:      "failing choice on the failing branch",
+		syntax:     `a = "123"; b:root = a | "13"`,
+		text:       "124",
+		offset:     2,
+		column:     2,
+		definition: "a",
+	}, {
+		title:      "failing choice on a shorter branch",
+		syntax:     `a = "13"; b:root = "123" | a`,
+		text:       "124",
+		offset:     2,
+		column:     2,
+		definition: "b",
+	}, {
+		title:      "longer failure on a later pass",
+		syntax:     `a = "12"; b = "34"; c = "1" b; d:root = a | c`,
+		text:       "135",
+		offset:     2,
+		column:     2,
+		definition: "b",
+	}, {
+		title:      "char as a choice option",
+		syntax:     `a = "12"; b = [a] | [b]; c = a b`,
+		text:       "12c",
+		offset:     2,
+		column:     2,
+		definition: "b",
 	}} {
 		t.Run(test.title, func(t *testing.T) {
 			s, err := openSyntaxString(test.syntax)
@@ -81,6 +109,7 @@ func TestError(t *testing.T) {
 				return
 			}
 
+			// println("starting")
 			_, err = s.Parse(bytes.NewBufferString(test.text))
 			if err == nil {
 				t.Error("failed to fail")
@@ -119,8 +148,28 @@ func TestError(t *testing.T) {
 	}
 }
 
+func TestErrorRecursive(t *testing.T) {
+	const doc = `a[b][1a]`
+
+	s, err := openSyntaxFile("examples/mml.treerack")
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	// println("starting")
+	_, err = s.Parse(bytes.NewBufferString(doc))
+	perr, ok := err.(*ParseError)
+	if !ok {
+		t.Error("failed to return parse error")
+		return
+	}
+
+	t.Log(perr)
+}
+
 func TestErrorMessage(t *testing.T) {
-	const expected = "foo:4:10:failed to parse definition: bar"
+	const expected = "foo:4:10:failed to parse input, expecting: bar"
 
 	perr := &ParseError{
 		Input:      "foo",

sequence.go

@@ -312,7 +312,8 @@ func (p *sequenceParser) parse(c *context) {
 		p.items[itemIndex].parse(c)
 		if !c.matchLast {
 			if currentCount < p.ranges[itemIndex][0] {
-				c.recordFailure(p)
+				// println("recording sequence failure", p.name, c.offset)
+				c.recordFailure(c.offset, p)
 				c.fail(from)
 				if !p.allChars {
 					c.results.unmarkPending(from, p.id)

syntax.go

@@ -159,7 +159,7 @@ func intsContain(is []int, i int) bool {
 
 func (pe *ParseError) Error() string {
 	return fmt.Sprintf(
-		"%s:%d:%d:failed to parse definition: %s",
+		"%s:%d:%d:failed to parse input, expecting: %s",
 		pe.Input,
 		pe.Line+1,
 		pe.Column+1,