2 files changed, 90 insertions, 0 deletions
diff --git a/debug/frames.go b/debug/frames.go
new file mode 100644
index 0000000..88a48f0
--- /dev/null
+++ b/debug/frames.go
@@ -0,0 +1,66 @@
+package debug
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strings"
+)
+
+var varRegex = regexp.MustCompile(`(?:var)?\s*(\w*)\s*:?=`)
+
+func getPackageName(f runtime.Frame) string {
+	parts := strings.Split(f.Func.Name(), ".")
+	pl := len(parts)
+
+	if parts[pl-2][0] == '(' {
+		return strings.Join(parts[0:pl-2], ".")
+	} else {
+		return strings.Join(parts[0:pl-1], ".")
+	}
+}
+
+func getVarName(filename string, lineNo int) string {
+	f, err := os.Open(filename)
+	if err != nil {
+		return ""
+	}
+
+	scanner := bufio.NewScanner(f)
+	for i := 0; i < lineNo; i++ {
+		scanner.Scan()
+	}
+
+	line := scanner.Text()
+	if matches := varRegex.FindStringSubmatch(line); matches != nil {
+		return matches[1]
+	}
+	return ""
+}
+
+// GetDefinition returns the name of the variable and location this parser was defined by walking up the stack
+func GetDefinition() (varName string, location string) {
+	pc := make([]uintptr, 64)
+	n := runtime.Callers(3, pc)
+	frames := runtime.CallersFrames(pc[:n])
+
+	var frame runtime.Frame
+	more := true
+	for more {
+		frame, more = frames.Next()
+		pkg := getPackageName(frame)
+		if pkg == "github.com/vektah/goparsify" || pkg == "github.com/vektah/goparsify/debug" {
+			continue
+		}
+
+		varName := getVarName(frame.File, frame.Line)
+		if varName != "" {
+			return varName, fmt.Sprintf("%s:%d", filepath.Base(frame.File), frame.Line)
+		}
+	}
+
+	return "", ""
+}
diff --git a/debug/frames_test.go b/debug/frames_test.go
new file mode 100644
index 0000000..40c1086
--- /dev/null
+++ b/debug/frames_test.go
@@ -0,0 +1,24 @@
+package debug
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRegex(t *testing.T) {
+	tests := map[string]string{
+		"attrs": `	attrs = Map(Some(attr), func(node Result) Result {`,
+		"_value": `	_value = Any(_null, _true, _false, _string, _number, _array, _object)`,
+		"_object": `_object = Map(Seq("{", Cut, _properties, "}"), func(n Result) Result {`,
+		"expr":    `var expr = Exact("foo")`,
+		"number":  `number := NumberLit()`,
+	}
+	for expected, input := range tests {
+		t.Run(input, func(t *testing.T) {
+			matches := varRegex.FindStringSubmatch(input)
+			require.NotNil(t, matches)
+			require.Equal(t, expected, matches[1])
+		})
+	}
+}