Only try to resolve ENS names on mainnet

docs/middleware.rst

@@ -40,6 +40,11 @@ AttributeDict
     address that the name points to. For example :meth:`~web3.Eth.sendTransaction` will
     accept .eth names in the 'from' and 'to' fields.
 
+.. note::
+    This middleware only converts ENS names if invoked with the mainnet
+    (where the ENS contract is deployed), for all other cases will result in an
+    ``InvalidAddress`` error
+
 Pythonic
 ~~~~~~~~~~~~
 

tests/core/middleware/test_name_to_address_middleware.py

@@ -0,0 +1,56 @@
+import pytest
+
+from web3 import Web3
+from web3.exceptions import (
+    InvalidAddress,
+)
+from web3.middleware import (  # noqa: F401
+    construct_fixture_middleware,
+    name_to_address_middleware,
+)
+from web3.providers.base import (
+    BaseProvider,
+)
+
+NAME = "dump.eth"
+ADDRESS = "0x0000000000000000000000000000000000000000"
+BALANCE = 0
+
+
+class TempENS():
+    def __init__(self, name_addr_pairs):
+        self.registry = dict(name_addr_pairs)
+
+    def address(self, name, guess_tld=True):
+        # no automated web3 usages should be guessing the TLD
+        assert not guess_tld
+        return self.registry.get(name, None)
+
+
+@pytest.fixture
+def w3():
+    w3 = Web3(providers=[BaseProvider()], middlewares=[])
+    w3.ens = TempENS({NAME: ADDRESS})
+    w3.middleware_stack.add(name_to_address_middleware(w3))
+    return w3
+
+
+def test_pass_name_resolver(w3):
+    return_chain_on_mainnet = construct_fixture_middleware({
+        'net_version': '1',
+    })
+    return_balance = construct_fixture_middleware({
+        'eth_getBalance': BALANCE
+    })
+    w3.middleware_stack.inject(return_chain_on_mainnet, layer=0)
+    w3.middleware_stack.inject(return_balance, layer=0)
+    assert w3.eth.getBalance(NAME) == BALANCE
+
+
+def test_fail_name_resolver(w3):
+    return_chain_on_mainnet = construct_fixture_middleware({
+        'net_version': '2',
+    })
+    w3.middleware_stack.inject(return_chain_on_mainnet, layer=0)
+    with pytest.raises(InvalidAddress, match='.*ethereum\.eth.*'):
+        w3.eth.getBalance("ethereum.eth")

web3/utils/normalizers.py

@@ -31,6 +31,7 @@
     to_text,
 )
 from web3.utils.ens import (
+    StaticENS,
     is_ens_name,
     validate_name_has_address,
 )
@@ -134,9 +135,20 @@ def abi_address_to_hex(abi_type, data):
 def abi_ens_resolver(w3, abi_type, val):
     if abi_type == 'address' and is_ens_name(val):
         if w3 is None:
-            raise InvalidAddress("Could not look up name, because no web3 connection available")
+            raise InvalidAddress(
+                "Could not look up name %r because no web3"
+                " connection available" % (val)
+            )
         elif w3.ens is None:
-            raise InvalidAddress("Could not look up name, because ENS is set to None")
+            raise InvalidAddress(
+                "Could not look up name %r because ENS is"
+                " set to None" % (val)
+            )
+        elif int(w3.net.version) is not 1 and not isinstance(w3.ens, StaticENS):
+            raise InvalidAddress(
+                "Could not look up name %r because web3 is"
+                " not connected to mainnet" % (val)
+            )
         else:
             return (abi_type, validate_name_has_address(w3.ens, val))
     else: