klippy: Add ConfigWrapper.getchoice method

Add helper function that ensures a config option is one of several
choices.  This helps ensure that a proper error is raised if an
invalid choice is made.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/heater.py

@@ -26,7 +26,7 @@ class PrinterHeater:
         self.printer = printer
         self.config = config
         self.mcu_pwm = self.mcu_adc = None
-        self.thermistor_c = Thermistors.get(config.get('thermistor_type'))
+        self.thermistor_c = config.getchoice('thermistor_type', Thermistors)
         self.pullup_r = config.getfloat('pullup_resistor', 4700.)
         self.min_extrude_temp = config.getfloat('min_extrude_temp', 170.)
         self.can_extrude = (self.min_extrude_temp <= 0.)
@@ -48,9 +48,8 @@ class PrinterHeater:
         self.mcu_adc.set_minmax(
             SAMPLE_TIME, SAMPLE_COUNT, minval=min_adc, maxval=max_adc)
         self.mcu_adc.set_adc_callback(REPORT_TIME, self.adc_callback)
-        control_algo = self.config.get('control', 'watermark')
         algos = {'watermark': ControlBangBang, 'pid': ControlPID}
-        self.control = algos[control_algo](self, self.config)
+        self.control = self.config.getchoice('control', algos)(self, self.config)
         if self.printer.mcu.is_fileoutput():
             self.can_extrude = True
     def set_pwm(self, read_time, value):

klippy/klippy.py

@@ -61,6 +61,13 @@ class ConfigWrapper:
     def getboolean(self, option, default=sentinel):
         return self.get_wrapper(
             self.printer.fileconfig.getboolean, option, default)
+    def getchoice(self, option, choices, default=sentinel):
+        c = self.get(option, default)
+        if c not in choices:
+            raise self.error(
+                "Option '%s' in section '%s' is not a valid choice" % (
+                    option, self.section))
+        return choices[c]
     def getsection(self, section):
         return ConfigWrapper(self.printer, section)
 

klippy/toolhead.py

@@ -161,8 +161,7 @@ class ToolHead:
         self.extruder = printer.objects.get('extruder')
         kintypes = {'cartesian': cartesian.CartKinematics,
                     'delta': delta.DeltaKinematics}
-        kin = config.get('kinematics', 'cartesian')
-        self.kin = kintypes[kin](printer, config)
+        self.kin = config.getchoice('kinematics', kintypes)(printer, config)
         self.max_speed, self.max_accel = self.kin.get_max_speed()
         self.junction_deviation = config.getfloat('junction_deviation', 0.02)
         self.move_queue = MoveQueue()