feat: Add more details to MissingTargetException error (#189)

* feat: more detailed function target error message

Signed-off-by: Grant Timmerman <744973+grant@users.noreply.github.com>

* feat: more detailed function target error message (2)

Signed-off-by: Grant Timmerman <744973+grant@users.noreply.github.com>

* ci: fix tests

Signed-off-by: Grant Timmerman <744973+grant@users.noreply.github.com>

* ci: fix ci

Signed-off-by: Grant Timmerman <744973+grant@users.noreply.github.com>

Author: grant

src/functions_framework/_function_registry.py

@@ -38,16 +38,21 @@ def get_user_function(source, source_module, target):
     """Returns user function, raises exception for invalid function."""
     # Extract the target function from the source file
     if not hasattr(source_module, target):
+        non_target_functions = ", ".join(
+            "'{attr}'".format(attr=attr)
+            for attr in dir(source_module)
+            if isinstance(getattr(source_module, attr), types.FunctionType)
+        )
         raise MissingTargetException(
-            "File {source} is expected to contain a function named {target}".format(
-                source=source, target=target
+            "File {source} is expected to contain a function named '{target}'. Found: {non_target_functions} instead".format(
+                source=source, target=target, non_target_functions=non_target_functions
             )
         )
     function = getattr(source_module, target)
     # Check that it is a function
     if not isinstance(function, types.FunctionType):
         raise InvalidTargetTypeException(
-            "The function defined in file {source} as {target} needs to be of "
+            "The function defined in file {source} as '{target}' needs to be of "
             "type function. Got: invalid type {target_type}".format(
                 source=source, target=target, target_type=type(function)
             )

tests/test_functions.py

@@ -275,7 +275,8 @@ def test_invalid_function_definition_multiple_entry_points():
         create_app(target, source, "event")
 
     assert re.match(
-        "File .* is expected to contain a function named function", str(excinfo.value)
+        "File .* is expected to contain a function named 'function'. Found: 'fun', 'myFunctionBar', 'myFunctionFoo' instead",
+        str(excinfo.value),
     )
 
 
@@ -287,7 +288,7 @@ def test_invalid_function_definition_multiple_entry_points_invalid_function():
         create_app(target, source, "event")
 
     assert re.match(
-        "File .* is expected to contain a function named invalidFunction",
+        "File .* is expected to contain a function named 'invalidFunction'. Found: 'fun', 'myFunctionBar', 'myFunctionFoo' instead",
         str(excinfo.value),
     )
 
@@ -300,7 +301,7 @@ def test_invalid_function_definition_multiple_entry_points_not_a_function():
         create_app(target, source, "event")
 
     assert re.match(
-        "The function defined in file .* as notAFunction needs to be of type "
+        "The function defined in file .* as 'notAFunction' needs to be of type "
         "function. Got: .*",
         str(excinfo.value),
     )