feat: add warnings mode for import/export handlers, commands

can now specify `--warn` for import/export CLI, to get diff email when
changes occur.

this also adds `get_import_handler()` and friends, via app provider.

also declare email settings for the 2 existing importers

tests/test_app.py

@@ -0,0 +1,126 @@
+# -*- coding: utf-8; -*-
+
+from wuttjamaican.testing import ConfigTestCase
+
+from wuttasync import app as mod
+from wuttasync.importing import ImportHandler
+from wuttasync.importing.csv import FromCsvToWutta
+
+
+class FromFooToBar(ImportHandler):
+    source_key = "foo"
+    target_key = "bar"
+
+
+class FromCsvToPoser(FromCsvToWutta):
+    pass
+
+
+class TestWuttaSyncAppProvider(ConfigTestCase):
+
+    def test_get_all_import_handlers(self):
+
+        # by default our custom handler is not found
+        handlers = self.app.get_all_import_handlers()
+        self.assertIn(FromCsvToWutta, handlers)
+        self.assertNotIn(FromFooToBar, handlers)
+
+        # make sure if we configure a custom handler, it is found
+        self.config.setdefault(
+            "wuttasync.importing.import.to_wutta.from_csv.handler",
+            "tests.test_app:FromFooToBar",
+        )
+        handlers = self.app.get_all_import_handlers()
+        self.assertIn(FromCsvToWutta, handlers)
+        self.assertIn(FromFooToBar, handlers)
+
+    def test_get_designated_import_handler_spec(self):
+
+        # fetch of unknown key returns none
+        spec = self.app.get_designated_import_handler_spec("test01")
+        self.assertIsNone(spec)
+
+        # unless we require it, in which case, error
+        self.assertRaises(
+            ValueError,
+            self.app.get_designated_import_handler_spec,
+            "test01",
+            require=True,
+        )
+
+        # we configure one for whatever key we like
+        self.config.setdefault(
+            "wuttasync.importing.test02.handler", "tests.test_app:FromBarToFoo"
+        )
+        spec = self.app.get_designated_import_handler_spec("test02")
+        self.assertEqual(spec, "tests.test_app:FromBarToFoo")
+
+        # we can also define a "default" designated handler
+        self.config.setdefault(
+            "wuttasync.importing.test03.default_handler",
+            "tests.test_app:FromBarToFoo",
+        )
+        spec = self.app.get_designated_import_handler_spec("test03")
+        self.assertEqual(spec, "tests.test_app:FromBarToFoo")
+
+    def test_get_designated_import_handlers(self):
+
+        # some designated handlers exist, but not our custom handler
+        handlers = self.app.get_designated_import_handlers()
+        csv_handlers = [
+            h for h in handlers if h.get_key() == "import.to_wutta.from_csv"
+        ]
+        self.assertEqual(len(csv_handlers), 1)
+        csv_handler = csv_handlers[0]
+        self.assertIsInstance(csv_handler, FromCsvToWutta)
+        self.assertFalse(isinstance(csv_handler, FromCsvToPoser))
+        self.assertFalse(
+            any([h.get_key() == "import.to_bar.from_foo" for h in handlers])
+        )
+        self.assertFalse(any([isinstance(h, FromFooToBar) for h in handlers]))
+        self.assertFalse(any([isinstance(h, FromCsvToPoser) for h in handlers]))
+        self.assertTrue(
+            any([h.get_key() == "import.to_versions.from_wutta" for h in handlers])
+        )
+
+        # but we can make custom designated
+        self.config.setdefault(
+            "wuttasync.importing.import.to_wutta.from_csv.handler",
+            "tests.test_app:FromCsvToPoser",
+        )
+        handlers = self.app.get_designated_import_handlers()
+        csv_handlers = [
+            h for h in handlers if h.get_key() == "import.to_wutta.from_csv"
+        ]
+        self.assertEqual(len(csv_handlers), 1)
+        csv_handler = csv_handlers[0]
+        self.assertIsInstance(csv_handler, FromCsvToWutta)
+        self.assertIsInstance(csv_handler, FromCsvToPoser)
+        self.assertTrue(
+            any([h.get_key() == "import.to_versions.from_wutta" for h in handlers])
+        )
+
+    def test_get_import_handler(self):
+
+        # make sure a basic fetch works
+        handler = self.app.get_import_handler("import.to_wutta.from_csv")
+        self.assertIsInstance(handler, FromCsvToWutta)
+        self.assertFalse(isinstance(handler, FromCsvToPoser))
+
+        # and make sure custom override works
+        self.config.setdefault(
+            "wuttasync.importing.import.to_wutta.from_csv.handler",
+            "tests.test_app:FromCsvToPoser",
+        )
+        handler = self.app.get_import_handler("import.to_wutta.from_csv")
+        self.assertIsInstance(handler, FromCsvToWutta)
+        self.assertIsInstance(handler, FromCsvToPoser)
+
+        # unknown importer cannot be found
+        handler = self.app.get_import_handler("bogus")
+        self.assertIsNone(handler)
+
+        # and if we require it, error will raise
+        self.assertRaises(
+            ValueError, self.app.get_import_handler, "bogus", require=True
+        )