(bugfix) Use a defined __hash__() for unhashable, unnamed middleware:

Fixes a bug where the middleware which are not hashable, classes or the
``build`` method of builder classes, end up being given the same
identifier when a name is not provided for the middleware in the onion.
This fixes the issue by defining a unique hash for the base
``Web3Middleware`` class and using that hash in the case where the
middleware is unhashable and therefore indistinguishable from another
middleware.

newsfragments/3463.bugfix.rst

@@ -0,0 +1 @@
+Specify a unique ``__hash__()`` for unhashable ``Web3Middleware`` types and use this hash as the middleware onion key when a name is not provided for the middleware. This fixes a bug where different middleware were given the same name and therefore raised errors.

web3/datastructures.py

@@ -182,7 +182,7 @@ def add(self, element: TValue, name: Optional[TKey] = None) -> None:
         if name is None:
             name = cast(TKey, element)
 
-        name = self._repr_if_not_hashable(name)
+        name = self._build_tkey(name)
 
         if name in self._queue:
             if name is element:
@@ -219,7 +219,7 @@ def inject(
             if name is None:
                 name = cast(TKey, element)
 
-            name = self._repr_if_not_hashable(name)
+            name = self._build_tkey(name)
 
             self._queue.move_to_end(name, last=False)
         elif layer == len(self._queue):
@@ -233,7 +233,7 @@ def clear(self) -> None:
         self._queue.clear()
 
     def replace(self, old: TKey, new: TKey) -> TValue:
-        old_name = self._repr_if_not_hashable(old)
+        old_name = self._build_tkey(old)
 
         if old_name not in self._queue:
             raise Web3ValueError(
@@ -248,15 +248,25 @@ def replace(self, old: TKey, new: TKey) -> TValue:
             self._queue[old_name] = new
         return to_be_replaced
 
-    def _repr_if_not_hashable(self, value: TKey) -> TKey:
+    @staticmethod
+    def _build_tkey(value: TKey) -> TKey:
         try:
             value.__hash__()
+            return value
         except TypeError:
-            value = cast(TKey, repr(value))
-        return value
+            # unhashable, unnamed elements
+            if not callable(value):
+                raise Web3TypeError(
+                    f"Expected a callable or hashable type, got {type(value)}"
+                )
+            # This will either be ``Web3Middleware`` class or the ``build`` method of a
+            # ``Web3MiddlewareBuilder``. Instantiate with empty ``Web3`` and use a
+            # unique identifier with the ``__hash__()`` as the TKey.
+            v = value(None)
+            return cast(TKey, f"{v.__class__}<{v.__hash__()}>")
 
     def remove(self, old: TKey) -> None:
-        old_name = self._repr_if_not_hashable(old)
+        old_name = self._build_tkey(old)
         if old_name not in self._queue:
             raise Web3ValueError("You can only remove something that has been added")
         del self._queue[old_name]
@@ -270,8 +280,8 @@ def middleware(self) -> Sequence[Any]:
         return [(val, key) for key, val in reversed(self._queue.items())]
 
     def _replace_with_new_name(self, old: TKey, new: TKey) -> None:
-        old_name = self._repr_if_not_hashable(old)
-        new_name = self._repr_if_not_hashable(new)
+        old_name = self._build_tkey(old)
+        new_name = self._build_tkey(new)
 
         self._queue[new_name] = new
         found_old = False
@@ -293,11 +303,11 @@ def __add__(self, other: Any) -> "NamedElementOnion[TKey, TValue]":
         return NamedElementOnion(cast(List[Any], combined.items()))
 
     def __contains__(self, element: Any) -> bool:
-        element_name = self._repr_if_not_hashable(element)
+        element_name = self._build_tkey(element)
         return element_name in self._queue
 
     def __getitem__(self, element: TKey) -> TValue:
-        element_name = self._repr_if_not_hashable(element)
+        element_name = self._build_tkey(element)
         return self._queue[element_name]
 
     def __len__(self) -> int:

web3/middleware/base.py

@@ -40,6 +40,14 @@ class Web3Middleware:
     def __init__(self, w3: Union["AsyncWeb3", "Web3"]) -> None:
         self._w3 = w3
 
+    def __hash__(self) -> int:
+        return hash(f"{self.__class__.__name__}({str(self.__dict__)})")
+
+    def __eq__(self, other: Any) -> bool:
+        if not isinstance(other, Web3Middleware):
+            return False
+        return self.__hash__() == other.__hash__()
+
     # -- sync -- #
 
     def wrap_make_request(self, make_request: "MakeRequestFn") -> "MakeRequestFn":