Merge pull request #1594 from realjohnward/issue1560

Issue1560

Author: kclowes

newsfragments/1594.bugfix.rst

@@ -0,0 +1,9 @@
+Fixed hasattr overloader method in the web3.ContractEvent, web3.ContractFunction,
+and web3.ContractCaller classes by implementing a try/except handler
+that returns False if an exception is raised in the __getattr__ overloader method
+(since __getattr__ HAS to be called in every __hasattr__ call).
+
+Created two new Exception classes, 'ABIEventFunctionNotFound' and 'ABIFunctionNotFound',
+which inherit from both AttributeError and MismatchedABI, and replaced the MismatchedABI
+raises in ContractEvent, ContractFunction, and ContractCaller with a raise to the created class
+in the __getattr__ overloader method of the object.

tests/core/contracts/test_contract_attributes.py

@@ -0,0 +1,48 @@
+import pytest
+
+from web3.exceptions import (
+    ABIEventFunctionNotFound,
+    ABIFunctionNotFound,
+)
+
+
+@pytest.fixture()
+def abi():
+    return '''[{"anonymous":false,"inputs":[{"indexed":false,"name":"value","type":"uint256"}],"name":"Increased","type":"function"}, {"anonymous":false,"inputs":[{"indexed":false,"name":"value","type":"uint256"}],"name":"Increased","type":"event"}]'''  # noqa: E501
+
+
+@pytest.mark.parametrize(
+    'attribute',
+    ('functions', 'events', 'caller')
+)
+def test_getattr(web3, abi, attribute):
+    contract = web3.eth.contract(abi=abi)
+    contract_attribute = getattr(contract, attribute)
+    assert getattr(contract_attribute, "Increased")
+
+
+@pytest.mark.parametrize(
+    'attribute,error', (
+        ('functions', ABIFunctionNotFound),
+        ('events', ABIEventFunctionNotFound),
+        ('caller', ABIFunctionNotFound),
+    )
+)
+def test_getattr_raises_error(web3, abi, attribute, error):
+    contract = web3.eth.contract(abi=abi)
+    contract_attribute = getattr(contract, attribute)
+
+    with pytest.raises(error):
+        getattr(contract_attribute, "Decreased")
+
+
+@pytest.mark.parametrize(
+    'attribute',
+    ('functions', 'events', 'caller')
+)
+def test_hasattr(web3, abi, attribute):
+    contract = web3.eth.contract(abi=abi)
+    contract_attribute = getattr(contract, attribute)
+
+    assert hasattr(contract_attribute, "Increased") is True
+    assert hasattr(contract_attribute, "Decreased") is False

web3/contract.py

@@ -110,6 +110,8 @@
     MutableAttributeDict,
 )
 from web3.exceptions import (
+    ABIEventFunctionNotFound,
+    ABIFunctionNotFound,
     BadFunctionCallOutput,
     BlockNumberOutofRange,
     FallbackNotFound,
@@ -185,7 +187,7 @@ def __getattr__(self, function_name: str) -> "ContractFunction":
                 "Are you sure you provided the correct contract abi?"
             )
         elif function_name not in self.__dict__['_functions']:
-            raise MismatchedABI(
+            raise ABIFunctionNotFound(
                 "The function '{}' was not found in this contract's abi. ".format(function_name),
                 "Are you sure you provided the correct contract abi?"
             )
@@ -195,6 +197,12 @@ def __getattr__(self, function_name: str) -> "ContractFunction":
     def __getitem__(self, function_name: str) -> ABIFunction:
         return getattr(self, function_name)
 
+    def __hasattr__(self, event_name: str) -> bool:
+        try:
+            return event_name in self.__dict__['_events']
+        except ABIFunctionNotFound:
+            return False
+
 
 class ContractEvents:
     """Class containing contract event objects
@@ -239,7 +247,7 @@ def __getattr__(self, event_name: str) -> "ContractEvent":
                 "Are you sure you provided the correct contract abi?"
             )
         elif event_name not in self.__dict__['_events']:
-            raise MismatchedABI(
+            raise ABIEventFunctionNotFound(
                 "The event '{}' was not found in this contract's abi. ".format(event_name),
                 "Are you sure you provided the correct contract abi?"
             )
@@ -257,6 +265,12 @@ def __iter__(self) -> Iterable["ContractEvent"]:
         for event in self._events:
             yield self[event['name']]
 
+    def __hasattr__(self, event_name: str) -> bool:
+        try:
+            return event_name in self.__dict__['_events']
+        except ABIEventFunctionNotFound:
+            return False
+
 
 class Contract:
     """Base class for Contract proxy classes.
@@ -1357,7 +1371,7 @@ def __getattr__(self, function_name: str) -> Any:
             )
         elif function_name not in set(fn['name'] for fn in self._functions):
             functions_available = ', '.join([fn['name'] for fn in self._functions])
-            raise MismatchedABI(
+            raise ABIFunctionNotFound(
                 "The function '{}' was not found in this contract's ABI. ".format(function_name),
                 "Here is a list of all of the function names found: ",
                 "{}. ".format(functions_available),
@@ -1366,6 +1380,12 @@ def __getattr__(self, function_name: str) -> Any:
         else:
             return super().__getattribute__(function_name)
 
+    def __hasattr__(self, event_name: str) -> bool:
+        try:
+            return event_name in self.__dict__['_events']
+        except ABIFunctionNotFound:
+            return False
+
     def __call__(
         self, transaction: TxParams=None, block_identifier: BlockIdentifier='latest'
     ) -> 'ContractCaller':

web3/exceptions.py

@@ -70,6 +70,22 @@ class MismatchedABI(Exception):
     pass
 
 
+class ABIEventFunctionNotFound(AttributeError, MismatchedABI):
+    """
+    Raised when an attempt is made to access an event
+    that does not exist in the ABI.
+    """
+    pass
+
+
+class ABIFunctionNotFound(AttributeError, MismatchedABI):
+    """
+    Raised when an attempt is made to access a function
+    that does not exist in the ABI.
+    """
+    pass
+
+
 class FallbackNotFound(Exception):
     """
     Raised when fallback function doesn't exist in contract.