Ignore parameters with default values, closes #1

README.md

@@ -72,6 +72,21 @@ combined = await FetchWithParams().both(
 )
 print(combined)
 ```
+### Parameters with default values are ignored
+
+You can opt a parameter out of the dependency injection mechanism by assigning it a default value:
+
+```python
+class IgnoreDefaultParameters(AsyncInjectAll):
+    async def go(self, calc1, x=5):
+        return calc1 + x
+
+    async def calc1(self):
+        return 5
+
+print(await IgnoreDefaultParameters().go())
+# Prints 10
+```
 
 ### AsyncInject and @inject
 

asyncinject/__init__.py

@@ -48,12 +48,21 @@ def __new__(cls, name, bases, attrs):
 
 
 def _make_method(method):
-    parameters = inspect.signature(method).parameters.keys()
+    parameters = inspect.signature(method).parameters
 
     @wraps(method)
     async def inner(self, **kwargs):
         # Any parameters not provided by kwargs are resolved from registry
-        to_resolve = [p for p in parameters if p not in kwargs and p != "self"]
+        to_resolve = [
+            p
+            for p in parameters
+            # Not already provided
+            if p not in kwargs
+            # Not self
+            and p != "self"
+            # Doesn't have a default value
+            and parameters[p].default is inspect._empty
+        ]
         missing = [p for p in to_resolve if p not in self._registry]
         assert (
             not missing

tests/test_asyncinject.py

@@ -66,6 +66,14 @@ async def calc2(self, param1):
         return 6 + param1
 
 
+class IgnoreDefaultParameters(AsyncInjectAll):
+    async def go(self, calc1, x=5):
+        return calc1 + x
+
+    async def calc1(self):
+        return 5
+
+
 @pytest.mark.asyncio
 async def test_simple():
     assert await Simple().one() == ["two", "one"]
@@ -103,6 +111,12 @@ async def test_parameters_passed_through():
     assert result == 12
 
 
+@pytest.mark.asyncio
+async def test_ignore_default_parameters():
+    result = await IgnoreDefaultParameters().go()
+    assert result == 10
+
+
 @pytest.mark.asyncio
 async def test_resolve():
     object = WithParameters()