chore(internal): add reflection helper function

src/finch/_utils/__init__.py

@@ -49,4 +49,7 @@
     maybe_transform as maybe_transform,
     async_maybe_transform as async_maybe_transform,
 )
-from ._reflection import function_has_argument as function_has_argument
+from ._reflection import (
+    function_has_argument as function_has_argument,
+    assert_signatures_in_sync as assert_signatures_in_sync,
+)

src/finch/_utils/_reflection.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import inspect
 from typing import Any, Callable
 
@@ -6,3 +8,35 @@ def function_has_argument(func: Callable[..., Any], arg_name: str) -> bool:
     """Returns whether or not the given function has a specific parameter"""
     sig = inspect.signature(func)
     return arg_name in sig.parameters
+
+
+def assert_signatures_in_sync(
+    source_func: Callable[..., Any],
+    check_func: Callable[..., Any],
+    *,
+    exclude_params: set[str] = set(),
+) -> None:
+    """Ensure that the signature of the second function matches the first."""
+
+    check_sig = inspect.signature(check_func)
+    source_sig = inspect.signature(source_func)
+
+    errors: list[str] = []
+
+    for name, source_param in source_sig.parameters.items():
+        if name in exclude_params:
+            continue
+
+        custom_param = check_sig.parameters.get(name)
+        if not custom_param:
+            errors.append(f"the `{name}` param is missing")
+            continue
+
+        if custom_param.annotation != source_param.annotation:
+            errors.append(
+                f"types for the `{name}` param are do not match; source={repr(source_param.annotation)} checking={repr(source_param.annotation)}"
+            )
+            continue
+
+    if errors:
+        raise AssertionError(f"{len(errors)} errors encountered when comparing signatures:\n\n" + "\n\n".join(errors))