CAM: snapmaker --machine is a required option

src/Mod/CAM/CAMTests/TestSnapmakerPost.py

@@ -238,10 +238,22 @@ M5
         )  # no TLO on Snapmaker (G43 inserted after tool change)
 
     def test_models(self):
-        """Test the various models."""
+        """Test the various models, and also test models that don't exist cause an error."""
         command = Path.Command("G0 X10 Y20 Z30")
         expected = "G0 X10.000 Y20.000 Z30.000"
 
+        with self.assertRaises(SystemExit):
+            self.get_gcode(
+                [command],
+                "--no-header",
+            )
+
+        with self.assertRaises(SystemExit):
+            gcode = self.get_gcode(
+                [command],
+                "--machine=robot --no-header",
+            )
+
         gcode = self.get_gcode(
             [command],
             "--machine=Original --toolhead=50W --spindle-percent --no-header",

src/Mod/CAM/Path/Post/scripts/snapmaker_post.py

@@ -179,7 +179,7 @@ class Snapmaker(Path.Post.Processor.PostProcessor):
         self.values["END_OF_LINE_CHARACTERS"] = "\n"
         self.values["FINISH_LABEL"] = "End"
         self.values["LINE_INCREMENT"] = 1
-        self.values["MACHINE_NAME"] = "Generic Snapmaker"
+        self.values["MACHINE_NAME"] = None
         self.values["MODAL"] = False
         self.values["OUTPUT_PATH_LABELS"] = True
         self.values["OUTPUT_HEADER"] = (
@@ -327,6 +327,7 @@ class Snapmaker(Path.Post.Processor.PostProcessor):
         group.add_argument(
             "--machine",
             default=None,
+            required=True,
             choices=self.values["MACHINES"].keys(),
             help=f"Snapmaker machine. Choose from [{self.values['MACHINES'].keys()}].",
         )
@@ -382,12 +383,12 @@ class Snapmaker(Path.Post.Processor.PostProcessor):
         if flag:  # process extra arguments only if flag is True
             self._units = self.values["UNITS"]
 
-            if args.machine:
-                machine = self.values["MACHINES"][args.machine]
-                self.values["MACHINE_KEY"] = machine["key"]
-                self.values["MACHINE_NAME"] = machine["name"]
-                # The deepcopy is necessary to avoid modifying the boundaries in the MACHINES dict.
-                self.values["BOUNDARIES"] = copy.deepcopy(machine["boundaries"])
+            # --machine is a required "option"
+            machine = self.values["MACHINES"][args.machine]
+            self.values["MACHINE_KEY"] = machine["key"]
+            self.values["MACHINE_NAME"] = machine["name"]
+            # The deepcopy is necessary to avoid modifying the boundaries in the MACHINES dict.
+            self.values["BOUNDARIES"] = copy.deepcopy(machine["boundaries"])
 
             if args.boundaries:  # may override machine boundaries, which is expected
                 self.values["BOUNDARIES"] = args.boundaries