[Experiment] extending features with addition pip package

dlt/feature/__init__.py

@@ -0,0 +1,10 @@
+try:
+    from dlt_example_plugin.feature import SupportsExtendedFeature as SupportsFeature
+    from dlt_example_plugin.feature import ExtendedFeature as Feature
+except ImportError:
+    from dlt.feature.reference import SupportsSimpleFeature as SupportsFeature
+    from dlt.feature.impl import SimpleFeature as Feature
+
+
+def get_feature() -> SupportsFeature:
+    return Feature()

dlt/feature/impl.py

@@ -0,0 +1,6 @@
+from dlt.feature.reference import SupportsSimpleFeature
+
+
+class SimpleFeature(SupportsSimpleFeature):
+    def calculate(self, a: int, b: int) -> int:
+        return a + b

dlt/feature/reference.py

@@ -0,0 +1,5 @@
+from typing import Protocol
+
+
+class SupportsSimpleFeature(Protocol):
+    def calculate(self, a: int, b: int) -> int: ...

tests/plugins/dlt_example_plugin/dlt_example_plugin/feature/__init__.py

@@ -0,0 +1,21 @@
+from typing import TYPE_CHECKING
+
+from dlt.feature.impl import SimpleFeature
+from dlt.feature.reference import SupportsSimpleFeature
+
+
+# extend interface
+class SupportsExtendedFeature(SupportsSimpleFeature):
+    # add new method
+    def more_calculation(self, a: int, b: int) -> int: ...
+
+
+# extend implementation
+class ExtendedFeature(SupportsExtendedFeature, SimpleFeature):
+    # override a method
+    def calculate(self, a: int, b: int) -> int:
+        return a * b
+
+    # add a new method
+    def more_calculation(self, a: int, b: int) -> int:
+        return a**b

tests/plugins/test_plugin_discovery.py

@@ -45,7 +45,10 @@ def plugin_install():
     sys.path.remove(temp_dir)
     shutil.rmtree(temp_dir)
     importlib.reload(importlib.metadata)
-    del container[plugins.PluginContext]
+    if plugins.PluginContext in container:
+        del container[plugins.PluginContext]
+
+
 
 
 def test_example_plugin() -> None:
@@ -83,3 +86,11 @@ def test_cli_hook(script_runner: ScriptRunner) -> None:
     assert result.returncode == -55
     assert "Plugin overwrote init command" in result.stdout
     assert "INIT_DOCS_URL" in result.stdout
+
+
+def test_extended_feature():
+    from dlt.feature import get_feature
+
+    feature = get_feature()
+    assert feature.calculate(3, 3) == 9
+    assert feature.more_calculation(3, 3) == 27

tests/plugins/test_simple_feature.py

@@ -0,0 +1,5 @@
+def test_simple_feature():
+    from dlt.feature import get_feature
+
+    feature = get_feature()
+    assert feature.calculate(3, 3) == 6