From 8fabdecb556354559f9dcc280c75001f3df8aaa8 Mon Sep 17 00:00:00 2001
From: Sebastian Berg <sebastian@sipsolutions.net>
Date: Fri, 10 Jun 2022 18:49:06 -0700
Subject: ENH: Ensure dispatcher TypeErrors report original name

This replaces the name in the TypeError with the actually raised
name.  In principle we could add one more check, because a
signature related TypeError must have a traceback with exactly
one entry (so `sys.exc_info()[2].tb_next is None`).
In practice this seems unnecessary though.

This ensures the following message:

    >>> np.histogram(asdf=3)
    TypeError: histogram() got an unexpected keyword argument 'asdf'

Closes gh-21647
---
 numpy/core/overrides.py            | 23 +++++++++++++++++++++-
 numpy/core/tests/test_overrides.py | 39 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)

(limited to 'numpy')

diff --git a/numpy/core/overrides.py b/numpy/core/overrides.py
index cb550152e..663436a4c 100644
--- a/numpy/core/overrides.py
+++ b/numpy/core/overrides.py
@@ -2,6 +2,7 @@
 import collections
 import functools
 import os
+import sys
 
 from numpy.core._multiarray_umath import (
     add_docstring, implement_array_function, _get_implementing_args)
@@ -176,7 +177,27 @@ def array_function_dispatch(dispatcher, module=None, verify=True,
 
         @functools.wraps(implementation)
         def public_api(*args, **kwargs):
-            relevant_args = dispatcher(*args, **kwargs)
+            try:
+                relevant_args = dispatcher(*args, **kwargs)
+            except TypeError as exc:
+                # Try to clean up a signature related TypeError.  Such an
+                # error will be something like:
+                #     dispatcher.__name__() got an unexpected keyword argument
+                #
+                # So replace the dispatcher name in this case.  In principle
+                # TypeErrors may be raised from _within_ the dispatcher, so
+                # we check that the traceback contains a string that starts
+                # with the name.  (In principle we could also check the
+                # traceback length, as it would be deeper.)
+                msg = exc.args[0]
+                disp_name = dispatcher.__name__
+                if not isinstance(msg, str) or not msg.startswith(disp_name):
+                    raise
+
+                # Replace with the correct name and re-raise:
+                new_msg = msg.replace(disp_name, public_api.__name__)
+                raise TypeError(new_msg) from None
+
             return implement_array_function(
                 implementation, public_api, relevant_args, args, kwargs)
 
diff --git a/numpy/core/tests/test_overrides.py b/numpy/core/tests/test_overrides.py
index 36970dbc0..e68406ebd 100644
--- a/numpy/core/tests/test_overrides.py
+++ b/numpy/core/tests/test_overrides.py
@@ -355,6 +355,45 @@ class TestArrayFunctionImplementation:
                 TypeError, "no implementation found for 'my.func'"):
             func(MyArray())
 
+    def test_signature_error_message(self):
+        # The lambda function will be named "<lambda>", but the TypeError
+        # should show the name as "func"
+        def _dispatcher():
+            return ()
+
+        @array_function_dispatch(_dispatcher)
+        def func():
+            pass
+
+        try:
+            func(bad_arg=3)
+        except TypeError as e:
+            expected_exception = e
+
+        try:
+            func(bad_arg=3)
+            raise AssertionError("must fail")
+        except TypeError as exc:
+            assert exc.args == expected_exception.args
+
+    @pytest.mark.parametrize("value", [234, "this func is not replaced"])
+    def test_dispatcher_error(self, value):
+        # If the dispatcher raises an error, we must not attempt to mutate it
+        error = TypeError(value)
+
+        def dispatcher():
+            raise error
+
+        @array_function_dispatch(dispatcher)
+        def func():
+            return 3
+
+        try:
+            func()
+            raise AssertionError("must fail")
+        except TypeError as exc:
+            assert exc is error  # unmodified exception
+
 
 class TestNDArrayMethods:
 
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