add revolutions check

components/motor/dimensionengineering/sabertooth.go

@@ -397,6 +397,10 @@ func (m *Motor) GoFor(ctx context.Context, rpm, revolutions float64, extra map[s
 		return motor.NewZeroRPMError()
 	}
 
+	if err := motor.CheckRevolutions(revolutions); err != nil {
+		return err
+	}
+
 	powerPct, waitDur := goForMath(m.maxRPM, rpm, revolutions)
 	err := m.SetPower(ctx, powerPct, extra)
 	if err != nil {

components/motor/errors.go

@@ -20,6 +20,12 @@ func NewZeroRPMError() error {
 	return errors.New("Cannot move motor at an RPM that is nearly 0")
 }
 
+// NewZeroRPMError returns an error representing a request to move a motor at
+// zero speed (i.e., moving the motor without moving the motor).
+func NewZeroRevsError() error {
+	return errors.New("Cannot move motor for 0 revolutions")
+}
+
 // NewGoToUnsupportedError returns error when a motor is required to support GoTo feature.
 func NewGoToUnsupportedError(motorName string) error {
 	return errors.Errorf("motor with name %s does not support GoTo", motorName)

components/motor/fake/motor.go

@@ -32,6 +32,7 @@ var (
 )
 
 const defaultMaxRpm = 100
+const defaultNonZeroRevs = -1
 
 // PinConfig defines the mapping of where motor are wired.
 type PinConfig struct {
@@ -300,6 +301,10 @@ func (m *Motor) GoFor(ctx context.Context, rpm, revolutions float64, extra map[s
 		return err
 	}
 
+	if err := motor.CheckRevolutions(revolutions); err != nil {
+		return err
+	}
+
 	powerPct, waitDur, dir := goForMath(m.MaxRPM, rpm, revolutions)
 
 	var finalPos float64
@@ -347,8 +352,9 @@ func (m *Motor) GoTo(ctx context.Context, rpm, pos float64, extra map[string]int
 	if err != nil {
 		return err
 	}
-	if curPos == pos {
-		return nil
+
+	if err := motor.CheckRevolutions(pos - curPos); err != nil {
+		return err
 	}
 
 	revolutions := pos - curPos

components/motor/gpio/basic.go

@@ -278,6 +278,10 @@ func (m *Motor) GoFor(ctx context.Context, rpm, revolutions float64, extra map[s
 		return err
 	}
 
+	if err := motor.CheckRevolutions(revolutions); err != nil {
+		return err
+	}
+
 	powerPct, waitDur := goForMath(m.maxRPM, rpm, revolutions)
 	err = m.SetPower(ctx, powerPct, extra)
 	if err != nil {

components/motor/gpio/controlled.go

@@ -318,6 +318,10 @@ func (cm *controlledMotor) GoFor(ctx context.Context, rpm, revolutions float64,
 		return err
 	}
 
+	if err := motor.CheckRevolutions(revolutions); err != nil {
+		return err
+	}
+
 	currentTicks, _, err := cm.enc.Position(ctx, encoder.PositionTypeTicks, extra)
 	if err != nil {
 		return err

components/motor/gpio/encoded.go

@@ -259,6 +259,10 @@ func (m *EncodedMotor) GoFor(ctx context.Context, rpm, revolutions float64, extr
 		return err
 	}
 
+	if err := motor.CheckRevolutions(revolutions); err != nil {
+		return err
+	}
+
 	goalPos, goalRPM, direction := encodedGoForMath(rpm, revolutions, currentTicks, m.ticksPerRotation)
 
 	if err := m.goForInternal(goalRPM, goalPos, direction); err != nil {

components/motor/gpiostepper/gpiostepper.go

@@ -357,6 +357,10 @@ func (m *gpioStepper) goForInternal(ctx context.Context, rpm, revolutions float6
 		return m.Stop(ctx, nil)
 	}
 
+	if err := motor.CheckRevolutions(revolutions); err != nil {
+		return err
+	}
+
 	var d int64 = 1
 	if math.Signbit(revolutions) != math.Signbit(rpm) {
 		d = -1

components/motor/motor.go

@@ -199,3 +199,11 @@ func CheckSpeed(rpm, max float64) (string, error) {
 		return "", nil
 	}
 }
+
+// CheckRevolutions checks if the input revolutions is non-zero
+func CheckRevolutions(revs float64) error {
+	if revs == 0 {
+		return NewZeroRevsError()
+	}
+	return nil
+}

components/motor/roboclaw/roboclaw.go

@@ -260,6 +260,10 @@ func (m *roboclawMotor) GoFor(ctx context.Context, rpm, revolutions float64, ext
 		return err
 	}
 
+	if err := motor.CheckRevolutions(revolutions); err != nil {
+		return err
+	}
+
 	// If no encoders present, distance traveled is estimated based on max RPM.
 	if m.conf.TicksPerRotation == 0 {
 		if math.Abs(rpm) > maxRPM {