Update rcfile and banner normalization.

Also remove tests for bogus assignment and add type hints instead.

This change moves the normalization from the property setters into
the getters. Doing this makes sure we are checking the data as it
comes in to the application rather than when it leaves the app.

This also means that we are trusting data generated from within
the app. And the type hints have been added to help check that
the implementation is correct.

envlauncher/app.py

@@ -155,8 +155,6 @@ def __init__(self, file_or_path):
         self._parser.read_string(string)
 
         self._terminal_emulator_choices = get_terminal_emulators()
-        self._rcfile = self._parser.get('X-EnvLauncher Options', 'Rcfile', fallback='')
-        self._banner = self._parser.get('X-EnvLauncher Options', 'Banner', fallback='color')
         self._venv_number = itertools.count(1)
         self._app_data_subdir = 'envlauncher'
 
@@ -209,13 +207,11 @@ def rcfile(self) -> str:
         """An "rc" file to execute after activating the environment
         (e.g., ~/.bashrc).
         """
-        return self._rcfile
+        return self._parser.get('X-EnvLauncher Options', 'Rcfile', fallback='')
 
     @rcfile.setter
-    def rcfile(self, value):
-        if not isinstance(value, str):
-            value = ''
-        self._rcfile = value
+    def rcfile(self, value: str):
+        self._parser['X-EnvLauncher Options']['Rcfile'] = value
 
     @property
     def terminal_emulator_choices(self) -> List[str]:
@@ -239,13 +235,14 @@ def terminal_emulator(self, value):
     @property
     def banner(self) -> str:
         """Python logo banner option."""
-        return self._banner
+        value = self._parser.get('X-EnvLauncher Options', 'Banner', fallback='')
+        if value not in {'color', 'plain', 'none'}:
+            return 'color'
+        return value
 
     @banner.setter
-    def banner(self, value):
-        if value not in {'color', 'plain', 'none'}:
-            value = 'color'
-        self._banner = value
+    def banner(self, value: str):
+        self._parser['X-EnvLauncher Options']['Banner'] = value
 
     @property
     def banner_resource(self) -> Optional[Tuple[str, str]]:

tests/test_app.py

@@ -259,10 +259,6 @@ def test_set_value(self):
         self.settings.rcfile = '.venvrc'
         self.assertEqual(self.settings.rcfile, '.venvrc')
 
-    def test_invalid_value(self):
-        self.settings.rcfile = 1234  # <- Bogus value.
-        self.assertEqual(self.settings.rcfile, '')  # <- Empty string.
-
 
 class TestSettingsTerminalEmulator(unittest.TestCase):
     def setUp(self):
@@ -309,17 +305,17 @@ def setUp(self):
     def test_read(self):
         self.assertEqual(self.settings.banner, 'color')
 
+    def test_read_bad_value(self):
+        self.settings.banner = 'some bad value'
+        self.assertEqual(self.settings.banner, 'color')
+
     def test_set_value(self):
         self.settings.banner = 'plain'
         self.assertEqual(self.settings.banner, 'plain')
 
         self.settings.banner = 'none'
         self.assertEqual(self.settings.banner, 'none')
 
-    def test_invalid_value(self):
-        self.settings.banner = 1234  # <- Bogus value.
-        self.assertEqual(self.settings.banner, 'color')  # <- Defaults to color.
-
     def test_banner_resource(self):
         self.assertEqual(self.settings.banner_resource,
                          ('envlauncher', 'banner-color.ascii'))