Fix bug where active layer list can become empty

* Fix bug where active layer list can become empty by combining MO and
  TO,
* add missing debug hook to `_to_pressed`,
* add some unit tests for the layer module,
* fix unit test result for empty reports.

kmk/modules/layers.py

@@ -126,7 +126,7 @@ def _to_pressed(self, key, keyboard, *args, **kwargs):
         '''
         self._active_combo = None
         keyboard.active_layers.clear()
-        keyboard.active_layers.insert(0, key.meta.layer)
+        self.activate_layer(keyboard, key.meta.layer)
 
     def _print_debug(self, keyboard):
         if debug.enabled:
@@ -150,15 +150,16 @@ def deactivate_layer(self, keyboard, layer):
         # This also resolves an issue where using DF() on a layer
         # triggered by MO() and then defaulting to the MO()'s layer
         # would result in no layers active.
-        try:
-            del_idx = keyboard.active_layers.index(layer)
-            del keyboard.active_layers[del_idx]
-        except ValueError:
-            if debug.enabled:
-                debug(f'_mo_released: layer {layer} not active')
-
-        if self.combo_layers:
-            self._deactivate_combo_layer(keyboard, layer)
+        if len(keyboard.active_layers) > 1:
+            try:
+                idx = keyboard.active_layers.index(layer)
+                del keyboard.active_layers[idx]
+            except ValueError:
+                if debug.enabled:
+                    debug(f'_mo_released: layer {layer} not active')
+
+            if self.combo_layers:
+                self._deactivate_combo_layer(keyboard, layer)
 
         self._print_debug(keyboard)
 

tests/keyboard_test.py

@@ -94,8 +94,8 @@ def test(self, testname, key_events, assert_reports, hid_send):
             try:
                 hid_report = hid_reports[i]
             except IndexError:
-                report_mods = None
-                report_keys = [None]
+                report_mods = 0
+                report_keys = set()
             else:
                 report_mods = hid_report[0]
                 report_keys = {code for code in hid_report[2:] if code != 0}

tests/test_layers.py

@@ -5,7 +5,7 @@
 from tests.keyboard_test import KeyboardTest
 
 
-class TestLayers(unittest.TestCase):
+class TestHoldTapLayers(unittest.TestCase):
     def setUp(self):
         self.kb = KeyboardTest(
             [Layers()],
@@ -48,5 +48,102 @@ def test_layertap(self):
         )
 
 
+class TestLayers(unittest.TestCase):
+    def setUp(self):
+        self.kb = KeyboardTest(
+            [Layers()],
+            [
+                [
+                    KC.N0,
+                    KC.DF(2),
+                    KC.MO(1),
+                    KC.TG(1),
+                    KC.TO(2),
+                ],
+                [KC.N1, KC.DF(0), None, KC.TRNS, KC.TO(1)],
+                [KC.N2, KC.DF(0)],
+            ],
+            debug_enabled=False,
+        )
+
+    def test_df_layer(self):
+        self.kb.test(
+            '',
+            [(1, True), (0, True)],
+            [{KC.N2}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [2])
+        self.kb.test(
+            '',
+            [(1, False), (0, False)],
+            [{}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [2])
+        self.kb.test('', [(1, True), (1, False)], [{}])
+
+    def test_mo_layer(self):
+        self.assertEqual(self.kb.keyboard.active_layers, [0])
+        self.kb.test(
+            '',
+            [(2, True), (0, True)],
+            [{KC.N1}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [1, 0])
+        self.kb.test(
+            '',
+            [(2, False), (0, False)],
+            [{}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [0])
+        self.kb.test(
+            '',
+            [(2, True), (4, True)],
+            [{}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [1])
+        self.kb.test(
+            '',
+            [(2, False), (4, False)],
+            [{}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [1])
+        self.kb.test('', [(1, True), (1, False)], [{}])
+
+    def test_tg_layer(self):
+        self.kb.test(
+            '',
+            [(3, True), (0, True)],
+            [{KC.N1}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [1, 0])
+        self.kb.test(
+            '',
+            [(3, False), (0, False)],
+            [{}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [1, 0])
+        self.kb.test(
+            '',
+            [(3, True)],
+            [{}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [0])
+
+    def test_to_layer(self):
+        self.kb.test(
+            '',
+            [(4, True), (0, True)],
+            [{KC.N2}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [2])
+        self.kb.test(
+            '',
+            [(4, False), (0, False)],
+            [{}],
+        )
+        self.assertEqual(self.kb.keyboard.active_layers, [2])
+        self.kb.test('', [(1, True), (1, False)], [{}])
+
+
 if __name__ == '__main__':
     unittest.main()