Add warnings for unresolved markers

docs/wiring.rst

@@ -251,6 +251,32 @@ To inject a container use special identifier ``<container>``:
    def foo(container: Container = Provide["<container>"]) -> None:
        ...
 
+Caveats
+~~~~~~~
+
+While using string identifiers you may not notice a typo in the identifier until the code is executed.
+In order to aid with catching such errors early, you may pass `warn_unresolved=True` to the ``wire`` method and/or :class:`WiringConfiguration`:
+
+.. code-block:: python
+   :emphasize-lines: 4
+
+   class Container(containers.DeclarativeContainer):
+       wiring_config = containers.WiringConfiguration(
+           modules=["yourapp.module"],
+           warn_unresolved=True,
+       )
+
+Or:
+
+.. code-block:: python
+   :emphasize-lines: 4
+
+   container = Container()
+   container.wire(
+       modules=["yourapp.module"],
+       warn_unresolved=True,
+   )
+
 
 Making injections into modules and class attributes
 ---------------------------------------------------

pyproject.toml

@@ -54,7 +54,7 @@ classifiers = [
 dynamic = ["version"]
 dependencies = [
     # typing.Annotated since v3.9
-    # typing.Self since v3.11
+    # typing.Self and typing.assert_never since v3.11
     "typing-extensions; python_version<'3.11'",
 ]
 

src/dependency_injector/containers.pyi

@@ -72,6 +72,7 @@ class Container:
         modules: Optional[Iterable[Any]] = None,
         packages: Optional[Iterable[Any]] = None,
         from_package: Optional[str] = None,
+        warn_unresolved: bool = False,
     ) -> None: ...
     def unwire(self) -> None: ...
     def init_resources(self, resource_type: Type[Resource[Any]] = Resource) -> Optional[Awaitable[None]]: ...

src/dependency_injector/containers.pyx

@@ -20,15 +20,31 @@ from .wiring import wire, unwire
 class WiringConfiguration:
     """Container wiring configuration."""
 
-    def __init__(self, modules=None, packages=None, from_package=None, auto_wire=True, keep_cache=False):
+    def __init__(
+        self,
+        modules=None,
+        packages=None,
+        from_package=None,
+        auto_wire=True,
+        keep_cache=False,
+        warn_unresolved=False,
+    ):
         self.modules = [*modules] if modules else []
         self.packages = [*packages] if packages else []
         self.from_package = from_package
         self.auto_wire = auto_wire
         self.keep_cache = keep_cache
+        self.warn_unresolved = warn_unresolved
 
     def __deepcopy__(self, memo=None):
-        return self.__class__(self.modules, self.packages, self.from_package, self.auto_wire, self.keep_cache)
+        return self.__class__(
+            self.modules,
+            self.packages,
+            self.from_package,
+            self.auto_wire,
+            self.keep_cache,
+            self.warn_unresolved,
+        )
 
 
 class Container:
@@ -259,7 +275,14 @@ class DynamicContainer(Container):
         """Check if auto wiring is needed."""
         return self.wiring_config.auto_wire is True
 
-    def wire(self, modules=None, packages=None, from_package=None, keep_cache=None):
+    def wire(
+        self,
+        modules=None,
+        packages=None,
+        from_package=None,
+        keep_cache=None,
+        warn_unresolved=False,
+    ):
         """Wire container providers with provided packages and modules.
 
         :rtype: None
@@ -298,6 +321,7 @@ class DynamicContainer(Container):
             modules=modules,
             packages=packages,
             keep_cache=keep_cache,
+            warn_unresolved=warn_unresolved,
         )
 
         if modules:

src/dependency_injector/wiring.py

@@ -25,15 +25,14 @@ from typing import (
     Type,
     TypeVar,
     Union,
-    assert_never,
     cast,
 )
 from warnings import warn
 
 try:
-    from typing import Self
+    from typing import Self, assert_never
 except ImportError:
-    from typing_extensions import Self
+    from typing_extensions import Self, assert_never
 
 try:
     from functools import cache
@@ -140,6 +139,10 @@ class DIWiringWarning(RuntimeWarning):
     """Base class for all warnings raised by the wiring module."""
 
 
+class UnresolvedMarkerWarning(DIWiringWarning):
+    """Warning raised when a marker with string identifier cannot be resolved against container."""
+
+
 class PatchedRegistry:
 
     def __init__(self) -> None:
@@ -434,6 +437,7 @@ def wire(  # noqa: C901
     modules: Optional[Iterable[ModuleType]] = None,
     packages: Optional[Iterable[ModuleType]] = None,
     keep_cache: bool = False,
+    warn_unresolved: bool = False,
 ) -> None:
     """Wire container providers with provided packages and modules."""
     modules = [*modules] if modules else []
@@ -450,9 +454,23 @@ def wire(  # noqa: C901
                 continue
 
             if _is_marker(member):
-                _patch_attribute(module, member_name, member, providers_map)
+                _patch_attribute(
+                    module,
+                    member_name,
+                    member,
+                    providers_map,
+                    warn_unresolved=warn_unresolved,
+                    warn_unresolved_stacklevel=1,
+                )
             elif inspect.isfunction(member):
-                _patch_fn(module, member_name, member, providers_map)
+                _patch_fn(
+                    module,
+                    member_name,
+                    member,
+                    providers_map,
+                    warn_unresolved=warn_unresolved,
+                    warn_unresolved_stacklevel=1,
+                )
             elif inspect.isclass(member):
                 cls = member
                 try:
@@ -464,15 +482,30 @@ def wire(  # noqa: C901
                     for cls_member_name, cls_member in cls_members:
                         if _is_marker(cls_member):
                             _patch_attribute(
-                                cls, cls_member_name, cls_member, providers_map
+                                cls,
+                                cls_member_name,
+                                cls_member,
+                                providers_map,
+                                warn_unresolved=warn_unresolved,
+                                warn_unresolved_stacklevel=1,
                             )
                         elif _is_method(cls_member):
                             _patch_method(
-                                cls, cls_member_name, cls_member, providers_map
+                                cls,
+                                cls_member_name,
+                                cls_member,
+                                providers_map,
+                                warn_unresolved=warn_unresolved,
+                                warn_unresolved_stacklevel=1,
                             )
 
         for patched in _patched_registry.get_callables_from_module(module):
-            _bind_injections(patched, providers_map)
+            _bind_injections(
+                patched,
+                providers_map,
+                warn_unresolved=warn_unresolved,
+                warn_unresolved_stacklevel=1,
+            )
 
     if not keep_cache:
         clear_cache()
@@ -525,6 +558,8 @@ def _patch_fn(
     name: str,
     fn: Callable[..., Any],
     providers_map: ProvidersMap,
+    warn_unresolved: bool = False,
+    warn_unresolved_stacklevel: int = 0,
 ) -> None:
     if not _is_patched(fn):
         reference_injections, reference_closing = _fetch_reference_injections(fn)
@@ -532,7 +567,12 @@ def _patch_fn(
             return
         fn = _get_patched(fn, reference_injections, reference_closing)
 
-    _bind_injections(fn, providers_map)
+    _bind_injections(
+        fn,
+        providers_map,
+        warn_unresolved=warn_unresolved,
+        warn_unresolved_stacklevel=warn_unresolved_stacklevel + 1,
+    )
 
     setattr(module, name, fn)
 
@@ -542,6 +582,8 @@ def _patch_method(
     name: str,
     method: Callable[..., Any],
     providers_map: ProvidersMap,
+    warn_unresolved: bool = False,
+    warn_unresolved_stacklevel: int = 0,
 ) -> None:
     if (
         hasattr(cls, "__dict__")
@@ -559,7 +601,12 @@ def _patch_method(
             return
         fn = _get_patched(fn, reference_injections, reference_closing)
 
-    _bind_injections(fn, providers_map)
+    _bind_injections(
+        fn,
+        providers_map,
+        warn_unresolved=warn_unresolved,
+        warn_unresolved_stacklevel=warn_unresolved_stacklevel + 1,
+    )
 
     if fn is method:
         # Hotfix, see: https://github.com/ets-labs/python-dependency-injector/issues/884
@@ -595,9 +642,17 @@ def _patch_attribute(
     name: str,
     marker: "_Marker",
     providers_map: ProvidersMap,
+    warn_unresolved: bool = False,
+    warn_unresolved_stacklevel: int = 0,
 ) -> None:
     provider = providers_map.resolve_provider(marker.provider, marker.modifier)
     if provider is None:
+        if warn_unresolved:
+            warn(
+                f"Unresolved marker {name} in {member!r}",
+                UnresolvedMarkerWarning,
+                stacklevel=warn_unresolved_stacklevel + 2,
+            )
         return
 
     _patched_registry.register_attribute(PatchedAttribute(member, name, marker))
@@ -674,7 +729,12 @@ def _fetch_reference_injections(  # noqa: C901
     return injections, closing
 
 
-def _bind_injections(fn: Callable[..., Any], providers_map: ProvidersMap) -> None:
+def _bind_injections(
+    fn: Callable[..., Any],
+    providers_map: ProvidersMap,
+    warn_unresolved: bool = False,
+    warn_unresolved_stacklevel: int = 0,
+) -> None:
     patched_callable = _patched_registry.get_callable(fn)
     if patched_callable is None:
         return
@@ -683,6 +743,12 @@ def _bind_injections(fn: Callable[..., Any], providers_map: ProvidersMap) -> Non
         provider = providers_map.resolve_provider(marker.provider, marker.modifier)
 
         if provider is None:
+            if warn_unresolved:
+                warn(
+                    f"Unresolved marker {injection} in {fn.__qualname__}",
+                    UnresolvedMarkerWarning,
+                    stacklevel=warn_unresolved_stacklevel + 2,
+                )
             continue
 
         if isinstance(marker, Provide):

tests/unit/samples/wiringstringids/missing.py

@@ -0,0 +1,15 @@
+from dependency_injector.wiring import Provide, inject
+
+missing_obj: object = Provide["missing"]
+
+
+class TestMissingClass:
+    obj: object = Provide["missing"]
+
+    def method(self, obj: object = Provide["missing"]) -> object:
+        return obj
+
+
+@inject
+def test_missing_function(obj: object = Provide["missing"]):
+    return obj

tests/unit/wiring/string_ids/test_main_py36.py

@@ -3,13 +3,19 @@
 import re
 from decimal import Decimal
 
-from pytest import fixture, mark, raises
+from pytest import fixture, mark, raises, warns
 from samples.wiringstringids import module, package, resourceclosing
 from samples.wiringstringids.container import Container, SubContainer
 from samples.wiringstringids.service import Service
 
 from dependency_injector import errors
-from dependency_injector.wiring import Closing, Provide, Provider, wire
+from dependency_injector.wiring import (
+    Closing,
+    Provide,
+    Provider,
+    UnresolvedMarkerWarning,
+    wire,
+)
 
 
 @fixture(autouse=True)
@@ -73,6 +79,16 @@ def test_module_attribute_wiring_with_invalid_marker(container: Container):
         container.wire(modules=[module_invalid_attr_injection])
 
 
+def test_warn_unresolved_marker(container: Container):
+    from samples.wiringstringids import missing
+
+    with warns(
+        UnresolvedMarkerWarning,
+        match=r"^Unresolved marker .+ in .+$",
+    ):
+        container.wire(modules=[missing], warn_unresolved=True)
+
+
 def test_class_wiring():
     test_class_object = module.TestClass()
     assert isinstance(test_class_object.service, Service)