From b22c4296f70ea9bf59cc1c8e6c34346489046338 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Thu, 8 Aug 2024 10:40:37 +0200
Subject: [PATCH] Verbose error handling for non-valid duckarrays (#9314)

* Add helpful error for non-duckarrays

* Add proof of concept

* Update test_namedarray.py

* Update test_namedarray.py

* Update test_namedarray.py

* remove test

* Update test_namedarray.py
---
 xarray/tests/test_namedarray.py | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/xarray/tests/test_namedarray.py b/xarray/tests/test_namedarray.py
index 7687765e659..8ccf8c541b7 100644
--- a/xarray/tests/test_namedarray.py
+++ b/xarray/tests/test_namedarray.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import copy
+import sys
 from abc import abstractmethod
 from collections.abc import Mapping
 from typing import TYPE_CHECKING, Any, Generic, cast, overload
@@ -86,7 +87,29 @@ def check_duck_array_typevar(a: duckarray[Any, _DType]) -> duckarray[Any, _DType
     if isinstance(b, _arrayfunction_or_api):
         return b
     else:
-        raise TypeError(f"a ({type(a)}) is not a valid _arrayfunction or _arrayapi")
+        missing_attrs = ""
+        actual_attrs = set(dir(b))
+        for t in _arrayfunction_or_api:
+            if sys.version_info >= (3, 13):
+                # https://github.com/python/cpython/issues/104873
+                from typing import get_protocol_members
+
+                expected_attrs = get_protocol_members(t)
+            elif sys.version_info >= (3, 12):
+                expected_attrs = t.__protocol_attrs__
+            else:
+                from typing import _get_protocol_attrs  # type: ignore[attr-defined]
+
+                expected_attrs = _get_protocol_attrs(t)
+
+            missing_attrs_ = expected_attrs - actual_attrs
+            if missing_attrs_:
+                missing_attrs += f"{t.__name__} - {missing_attrs_}\n"
+        raise TypeError(
+            f"a ({type(a)}) is not a valid _arrayfunction or _arrayapi. "
+            "Missing following attrs:\n"
+            f"{missing_attrs}"
+        )
 
 
 class NamedArraySubclassobjects: