Callers() []uintptr interface added

error.go

@@ -16,6 +16,7 @@ var DefaultCap = 20
 
 // Error is an error with stack trace.
 type Error interface {
+	Callers() []uintptr
 	Error() string
 	StackTrace() []Frame
 	Unwrap() error
@@ -38,6 +39,14 @@ func CustomError(err error, frames []Frame) Error {
 	}
 }
 
+// CustomErrorFromCallers creates an error with provided program counters.
+func CustomErrorFromCallers(err error, pcs []uintptr) Error {
+	return &errorData{
+		err: err,
+		pcs: pcs,
+	}
+}
+
 // Errorf creates new error with stacktrace and formatted message.
 // Formatting works the same way as in fmt.Errorf.
 func Errorf(message string, args ...interface{}) Error {
@@ -73,14 +82,19 @@ func Unwrap(err error) error {
 	return e.Unwrap()
 }
 
+// Callers returns raw program counters of the stack trace.
+func (e *errorData) Callers() []uintptr {
+	return e.pcs
+}
+
 // Error returns error message.
 func (e *errorData) Error() string {
 	return e.err.Error()
 }
 
 // StackTrace resolves and returns the stack trace, caching the result.
 func (e *errorData) StackTrace() []Frame {
-	if e.pcs == nil {
+	if e.frames != nil {
 		return e.frames
 	}
 	cf := runtime.CallersFrames(e.pcs)
@@ -97,7 +111,6 @@ func (e *errorData) StackTrace() []Frame {
 		}
 	}
 	e.frames = frames
-	e.pcs = nil
 	return e.frames
 }
 

error_test.go

@@ -235,6 +235,29 @@ func TestCustomError(t *testing.T) {
 	}
 }
 
+func TestCustomErrorFromCallers(t *testing.T) {
+	pcs := tracerr.New("some error").Callers()
+	err := tracerr.CustomErrorFromCallers(errors.New("custom"), pcs)
+	if len(err.Callers()) != len(pcs) {
+		t.Errorf("expected %d callers, got %d", len(pcs), len(err.Callers()))
+	}
+	if len(err.StackTrace()) == 0 {
+		t.Error("expected non-empty stack trace")
+	}
+}
+
+func TestCallers(t *testing.T) {
+	err := tracerr.New("some error")
+	pcs := err.Callers()
+	if len(pcs) == 0 {
+		t.Error("expected non-empty callers")
+	}
+	customErr := tracerr.CustomError(errors.New("custom"), nil)
+	if customErr.Callers() != nil {
+		t.Error("expected nil callers for CustomError")
+	}
+}
+
 func TestDeepStack(t *testing.T) {
 	var recurse func(n int) error
 	recurse = func(n int) error {