error message

context.go

@@ -103,7 +103,7 @@ func (c *context) recordFailure(p parser) {
 	}
 
 	c.failOffset = c.offset
-	if p.commitType()&userDefined != 0 {
+	if p.commitType()&userDefined != 0 && p.commitType()&Whitespace == 0 {
 		c.failingParser = p
 	}
 }

errors_test.go

@@ -93,6 +93,11 @@ func TestError(t *testing.T) {
 				return
 			}
 
+			if perr.Input != "<input>" {
+				t.Error("invalid default input name")
+				return
+			}
+
 			if perr.Offset != test.offset {
 				t.Error("invalid error offset", perr.Offset, test.offset)
 				return
@@ -113,3 +118,48 @@ func TestError(t *testing.T) {
 		})
 	}
 }
+
+func TestErrorMessage(t *testing.T) {
+	const expected = "foo:4:10:failed to parse definition: bar"
+
+	perr := &ParseError{
+		Input:      "foo",
+		Offset:     42,
+		Line:       3,
+		Column:     9,
+		Definition: "bar",
+	}
+
+	message := perr.Error()
+	if message != expected {
+		t.Error("failed to return the right error message")
+		t.Log("got:     ", message)
+		t.Log("expected:", expected)
+	}
+}
+
+func TestErrorVerbose(t *testing.T) {
+	const expected = `
+`
+
+	const doc = `{
+		"a": 1,
+		"b": 2,
+		"c": 3,
+	}`
+
+	s, err := openSyntaxFile("examples/json.treerack")
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	_, err = s.Parse(bytes.NewBufferString(doc))
+	perr, ok := err.(*ParseError)
+	if !ok {
+		t.Error("failed to return parse error")
+		return
+	}
+
+	t.Log(perr.Error())
+}

syntax.go

@@ -38,6 +38,10 @@ type SequenceItem struct {
 // the used syntax during parsing.
 type ParseError struct {
 
+	// Input is the name of the input file or <input> if not
+	// available.
+	Input string
+
 	// Offset is the index of the right-most failing
 	// token in the input text.
 	Offset int
@@ -55,6 +59,8 @@ type ParseError struct {
 
 	// Definition tells the right-most unmatched parser definition.
 	Definition string
+
+	registry *registry
 }
 
 type Syntax struct {
@@ -152,7 +158,17 @@ func intsContain(is []int, i int) bool {
 }
 
 func (pe *ParseError) Error() string {
-	return "parse error"
+	return fmt.Sprintf(
+		"%s:%d:%d:failed to parse definition: %s",
+		pe.Input,
+		pe.Line+1,
+		pe.Column+1,
+		pe.Definition,
+	)
+}
+
+func (pe *ParseError) Verbose() string {
+	return ""
 }
 
 func (s *Syntax) applyRoot(d definition) error {
@@ -354,6 +370,11 @@ func (s *Syntax) Parse(r io.Reader) (*Node, error) {
 	}
 
 	if err := c.finalizeParse(s.parser); err != nil {
+		if perr, ok := err.(*ParseError); ok {
+			perr.Input = "<input>"
+			perr.registry = s.registry
+		}
+
 		return nil, err
 	}