feat: improve error messages for annotation issues in command parameters

changelog/1411.feature.rst

@@ -0,0 +1 @@
+Improve error messaging when a command parameter's annotation cannot be resolved at runtime.

disnake/ext/commands/core.py

@@ -391,7 +391,16 @@ def callback(self, function: CommandCallback[CogT, Any, P, T]) -> None:
         except AttributeError:
             globalns = {}
 
-        params = get_signature_parameters(function, globalns, skip_standard_params=True)
+        try:
+            params = get_signature_parameters(function, globalns, skip_standard_params=True)
+        except NameError as e:
+            msg = (
+                str(e)
+                + ", please check all annotations are defined outside of TYPE_CHECKING blocks."
+            )
+            # todo: add name kw only argument once we use py310+
+            raise NameError(msg) from None
+
         for param in params.values():
             if param.annotation is Greedy:
                 msg = "Unparameterized Greedy[...] is disallowed in signature."

disnake/ext/commands/slash_core.py

@@ -306,7 +306,15 @@ def __init__(
         )
 
         if options is None:
-            options = expand_params(self)
+            try:
+                options = expand_params(self)
+            except NameError as e:
+                msg = (
+                    str(e)
+                    + ", please check all annotations are defined outside of TYPE_CHECKING blocks."
+                )
+                # todo: add name kw only argument once we use py310+
+                raise NameError(msg) from None
 
         self.docstring = utils.parse_docstring(func)
         desc_loc = Localized._cast(description, False)
@@ -473,7 +481,15 @@ def __init__(
         )
 
         if options is None:
-            options = expand_params(self)
+            try:
+                options = expand_params(self)
+            except NameError as e:
+                msg = (
+                    str(e)
+                    + ", please check all annotations are defined outside of TYPE_CHECKING blocks."
+                )
+                # todo: add name kw only argument once we use py310+
+                raise NameError(msg) from None
 
         self.docstring = utils.parse_docstring(func)
         desc_loc = Localized._cast(description, False)