Fix cache memory leaks

- `@cache` is stored in the Class, not in the Object. So when multiple `Safe` objects were created, and `get_contract()` was called, cache only increased (also if the same Safe was created multiple times)
- Use now `@cached_property`, which is binded to the object, so when the object is destroyed, so is the cached value
- Closes #322
- Related to #325

gnosis/safe/safe.py

@@ -42,11 +42,9 @@
 from .safe_tx import SafeTx
 
 try:
-    from functools import cache
+    from functools import cached_property
 except ImportError:
-    from functools import lru_cache
-
-    cache = lru_cache(maxsize=None)
+    from cached_property import cached_property
 
 
 logger = getLogger(__name__)
@@ -502,6 +500,15 @@ def build_safe_create2_tx(
 
         return safe_creation_tx
 
+    @cached_property
+    def contract(self) -> Contract:
+        v_1_3_0_contract = get_safe_V1_3_0_contract(self.w3, address=self.address)
+        version = v_1_3_0_contract.functions.VERSION().call()
+        if version == "1.3.0":
+            return v_1_3_0_contract
+        else:
+            return get_safe_V1_1_1_contract(self.w3, address=self.address)
+
     def check_funds_for_tx_gas(
         self, safe_tx_gas: int, base_gas: int, gas_price: int, gas_token: str
     ) -> bool:
@@ -542,7 +549,7 @@ def estimate_tx_base_gas(
         :return:
         """
         data = data or b""
-        safe_contract = self.get_contract()
+        safe_contract = self.contract
         threshold = self.retrieve_threshold()
         nonce = self.retrieve_nonce()
 
@@ -651,16 +658,14 @@ def parse_revert_data(result: bytes) -> int:
 
             return int(gas_estimation.hex(), 16)
 
-        tx = (
-            self.get_contract()
-            .functions.requiredTxGas(to, value, data, operation)
-            .build_transaction(
-                {
-                    "from": safe_address,
-                    "gas": 0,  # Don't call estimate
-                    "gasPrice": 0,  # Don't get gas price
-                }
-            )
+        tx = self.contract.functions.requiredTxGas(
+            to, value, data, operation
+        ).build_transaction(
+            {
+                "from": safe_address,
+                "gas": 0,  # Don't call estimate
+                "gasPrice": 0,  # Don't get gas price
+            }
         )
 
         tx_params = {
@@ -822,15 +827,6 @@ def estimate_tx_operational_gas(self, data_bytes_length: int):
         threshold = self.retrieve_threshold()
         return 15000 + data_bytes_length // 32 * 100 + 5000 * threshold
 
-    @cache
-    def get_contract(self) -> Contract:
-        v_1_3_0_contract = get_safe_V1_3_0_contract(self.w3, address=self.address)
-        version = v_1_3_0_contract.functions.VERSION().call()
-        if version == "1.3.0":
-            return v_1_3_0_contract
-        else:
-            return get_safe_V1_1_1_contract(self.w3, address=self.address)
-
     def retrieve_all_info(
         self, block_identifier: Optional[BlockIdentifier] = "latest"
     ) -> SafeInfo:
@@ -842,7 +838,7 @@ def retrieve_all_info(
         :raises: CannotRetrieveSafeInfoException
         """
         try:
-            contract = self.get_contract()
+            contract = self.contract
             master_copy = self.retrieve_master_copy_address()
             fallback_handler = self.retrieve_fallback_handler()
             guard = self.retrieve_guard()
@@ -938,7 +934,7 @@ def retrieve_modules(
         except BadFunctionCallOutput:
             pass
 
-        contract = self.get_contract()
+        contract = self.contract
         address = SENTINEL_ADDRESS
         all_modules: List[str] = []
         while True:
@@ -960,9 +956,9 @@ def retrieve_is_hash_approved(
         block_identifier: Optional[BlockIdentifier] = "latest",
     ) -> bool:
         return (
-            self.get_contract()
-            .functions.approvedHashes(owner, safe_hash)
-            .call(block_identifier=block_identifier)
+            self.contract.functions.approvedHashes(owner, safe_hash).call(
+                block_identifier=block_identifier
+            )
             == 1
         )
 
@@ -971,56 +967,40 @@ def retrieve_is_message_signed(
         message_hash: bytes,
         block_identifier: Optional[BlockIdentifier] = "latest",
     ) -> bool:
-        return (
-            self.get_contract()
-            .functions.signedMessages(message_hash)
-            .call(block_identifier=block_identifier)
+        return self.contract.functions.signedMessages(message_hash).call(
+            block_identifier=block_identifier
         )
 
     def retrieve_is_owner(
         self, owner: str, block_identifier: Optional[BlockIdentifier] = "latest"
     ) -> bool:
-        return (
-            self.get_contract()
-            .functions.isOwner(owner)
-            .call(block_identifier=block_identifier)
+        return self.contract.functions.isOwner(owner).call(
+            block_identifier=block_identifier
         )
 
     def retrieve_nonce(
         self, block_identifier: Optional[BlockIdentifier] = "latest"
     ) -> int:
-        return (
-            self.get_contract()
-            .functions.nonce()
-            .call(block_identifier=block_identifier)
-        )
+        return self.contract.functions.nonce().call(block_identifier=block_identifier)
 
     def retrieve_owners(
         self, block_identifier: Optional[BlockIdentifier] = "latest"
     ) -> List[str]:
-        return (
-            self.get_contract()
-            .functions.getOwners()
-            .call(block_identifier=block_identifier)
+        return self.contract.functions.getOwners().call(
+            block_identifier=block_identifier
         )
 
     def retrieve_threshold(
         self, block_identifier: Optional[BlockIdentifier] = "latest"
     ) -> int:
-        return (
-            self.get_contract()
-            .functions.getThreshold()
-            .call(block_identifier=block_identifier)
+        return self.contract.functions.getThreshold().call(
+            block_identifier=block_identifier
         )
 
     def retrieve_version(
         self, block_identifier: Optional[BlockIdentifier] = "latest"
     ) -> str:
-        return (
-            self.get_contract()
-            .functions.VERSION()
-            .call(block_identifier=block_identifier)
-        )
+        return self.contract.functions.VERSION().call(block_identifier=block_identifier)
 
     def build_multisig_tx(
         self,

gnosis/safe/tests/test_safe.py

@@ -572,9 +572,9 @@ def test_retrieve_guard(self):
 
         guard_address = Account.create().address
         set_guard_data = HexBytes(
-            safe.get_contract()
-            .functions.setGuard(guard_address)
-            .build_transaction({"gas": 1, "gasPrice": 1})["data"]
+            safe.contract.functions.setGuard(guard_address).build_transaction(
+                {"gas": 1, "gasPrice": 1}
+            )["data"]
         )
         set_guard_tx = safe.build_multisig_tx(safe.address, 0, set_guard_data)
         set_guard_tx.sign(owner_account.key)
@@ -629,7 +629,7 @@ def test_retrieve_all_info(self):
 
     def test_retrieve_modules(self):
         safe = self.deploy_test_safe(owners=[self.ethereum_test_account.address])
-        safe_contract = safe.get_contract()
+        safe_contract = safe.contract
         module_address = Account.create().address
         self.assertEqual(safe.retrieve_modules(), [])
 
@@ -663,7 +663,7 @@ def test_retrieve_modules(self):
 
     def test_retrieve_is_hash_approved(self):
         safe = self.deploy_test_safe(owners=[self.ethereum_test_account.address])
-        safe_contract = safe.get_contract()
+        safe_contract = safe.contract
         fake_tx_hash = Web3.keccak(text="Knopfler")
         another_tx_hash = Web3.keccak(text="Marc")
         tx = safe_contract.functions.approveHash(fake_tx_hash).build_transaction(
@@ -686,7 +686,7 @@ def test_retrieve_is_hash_approved(self):
 
     def test_retrieve_is_message_signed(self):
         safe = self.deploy_test_safe_v1_1_1(owners=[self.ethereum_test_account.address])
-        safe_contract = safe.get_contract()
+        safe_contract = safe.contract
         message = b"12345"
         message_hash = safe_contract.functions.getMessageHash(message).call()
         sign_message_data = HexBytes(

gnosis/safe/tests/test_safe_signature.py

@@ -182,7 +182,7 @@ def test_contract_signature(self):
         safe = self.deploy_test_safe_v1_1_1(
             owners=[owner_1.address], initial_funding_wei=Web3.toWei(0.01, "ether")
         )
-        safe_contract = safe.get_contract()
+        safe_contract = safe.contract
         safe_tx_hash = Web3.keccak(text="test")
         signature_r = HexBytes(safe.address.replace("0x", "").rjust(64, "0"))
         signature_s = HexBytes(
@@ -241,7 +241,7 @@ def test_contract_multiple_signatures(self):
         safe = self.deploy_test_safe_v1_1_1(
             owners=[owner_1.address], initial_funding_wei=Web3.toWei(0.01, "ether")
         )
-        safe_contract = safe.get_contract()
+        safe_contract = safe.contract
         safe_tx_hash = Web3.keccak(text="test")
 
         tx = safe_contract.functions.signMessage(safe_tx_hash).build_transaction(

gnosis/safe/tests/test_safe_tx.py

@@ -24,7 +24,7 @@ def test_multi_send_safe_tx(self):
             threshold=threshold,
             initial_funding_wei=self.w3.toWei(0.1, "ether"),
         )
-        safe_contract = safe.get_contract()
+        safe_contract = safe.contract
         to = self.multi_send_contract.address
         value = 0
         safe_tx_gas = 600000
@@ -273,22 +273,18 @@ def test_hash_safe_multisig_tx(self):
 
         safe = self.deploy_test_safe_v1_1_1()
         # Expected hash must be the same calculated by `getTransactionHash` of the contract
-        expected_hash = (
-            safe.get_contract()
-            .functions.getTransactionHash(
-                "0x5AC255889882aaB35A2aa939679E3F3d4Cea221E",
-                5212459,
-                HexBytes(0x00),
-                1,
-                123456,
-                122,
-                12345,
-                "0x" + "2" * 40,
-                "0x" + "2" * 40,
-                10789,
-            )
-            .call()
-        )
+        expected_hash = safe.contract.functions.getTransactionHash(
+            "0x5AC255889882aaB35A2aa939679E3F3d4Cea221E",
+            5212459,
+            HexBytes(0x00),
+            1,
+            123456,
+            122,
+            12345,
+            "0x" + "2" * 40,
+            "0x" + "2" * 40,
+            10789,
+        ).call()
         safe_tx_hash = SafeTx(
             self.ethereum_client,
             safe.address,
@@ -309,22 +305,18 @@ def test_hash_safe_multisig_tx(self):
         # Safe v1.3.0
         safe = self.deploy_test_safe()
         # Expected hash must be the same calculated by `getTransactionHash` of the contract
-        expected_hash = (
-            safe.get_contract()
-            .functions.getTransactionHash(
-                "0x5AC255889882aaB35A2aa939679E3F3d4Cea221E",
-                5212459,
-                HexBytes(0x00),
-                1,
-                123456,
-                122,
-                12345,
-                "0x" + "2" * 40,
-                "0x" + "2" * 40,
-                10789,
-            )
-            .call()
-        )
+        expected_hash = safe.contract.functions.getTransactionHash(
+            "0x5AC255889882aaB35A2aa939679E3F3d4Cea221E",
+            5212459,
+            HexBytes(0x00),
+            1,
+            123456,
+            122,
+            12345,
+            "0x" + "2" * 40,
+            "0x" + "2" * 40,
+            10789,
+        ).call()
         safe_tx_hash = SafeTx(
             self.ethereum_client,
             safe.address,