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Docs and refactoring from discussions on PR ethereum#2457
- Add documentation - Refactor out the provider flag since there is no support for sending transactions w/ CCIP Read support - Refactor some around the way the ``eth_call`` is made, add flag directly to ``eth_call`` and make ``durin_call()`` and internal ``_durin_call()``
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lines changed

‎docs/contracts.rst

+10
Original file line numberDiff line numberDiff line change
@@ -743,6 +743,16 @@ Positional and keyword arguments supplied to the contract function subclass
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will be used to find the contract function by signature,
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and forwarded to the contract function when applicable.
745745

746+
`EIP-3668 <https://eips.ethereum.org/EIPS/eip-3668>`_ introduced support for the ``OffchainLookup`` revert /
747+
CCIP Read support. The ``ccip_read_enabled`` flag is set to ``True`` for calls by default, as recommended in EIP-3668.
748+
If raising the ``OffchainLookup`` revert is preferred, the flag may be set to ``False`` on a per-call basis.
749+
750+
.. code-block:: python
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>>> myContract.functions.revertsWithOffchainLookup(myData).call(ccip_read_enabled=False)
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*** web3.exceptions.OffchainLookup
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746756
Methods
747757
~~~~~~~~~~
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‎docs/examples.rst

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@@ -624,6 +624,42 @@ When someone has an allowance they can transfer those tokens using the
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.. _ERC20: https://github.com/ethereum/EIPs/blob/7f4f0377730f5fc266824084188cc17cf246932e/EIPS/eip-20.md
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CCIP Read support for offchain lookup
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Contract calls support CCIP Read by default via a ``ccip_read_enabled`` flag that is set to a default value of ``True``.
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The following should work by default without raising the ``OffchainLookup`` and instead handling it appropriately as
632+
per the specification outlined in `EIP-3668 <https://eips.ethereum.org/EIPS/eip-3668>`_.
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.. code-block:: python
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myContract.functions.revertsWithOffchainLookup(myData).call()
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If the offchain lookup requires the user to send a transaction rather than make a call, this may be handled
639+
appropriately in the following way:
640+
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.. code-block:: python
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from web3 import Web3, WebsocketProvider
644+
from web3.utils import handle_offchain_lookup
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646+
w3 = Web3(WebsocketProvider(...))
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648+
myContract = w3.eth.contract(address=...)
649+
myData = b'data for offchain lookup function call'
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# preflight with an `eth_call` and handle the exception
652+
try:
653+
myContract.functions.revertsWithOffchainLookup(myData).call(ccip_read_enabled=False)
654+
except OffchainLookup as ocl:
655+
tx = {'to': myContract.address, 'from': my_account}
656+
data_for_callback_function = handle_offchain_lookup(ocl.payload)
657+
tx['data'] = data_for_callback_function
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# send the built transaction with either `eth_sendTransaction` or sign and send with `eth_sendRawTransaction`
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tx_hash = w3.eth.send_transaction(tx)
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662+
627663
Contract Unit Tests in Python
628664
-----------------------------
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‎docs/web3.eth.rst

+8
Original file line numberDiff line numberDiff line change
@@ -1090,6 +1090,14 @@ The following methods are available on the ``web3.eth`` namespace.
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View their `usage documentation <https://geth.ethereum.org/docs/rpc/ns-eth#3-object---state-override-set>`_
10911091
for a list of possible parameters.
10921092

1093+
EIP-3668 introduced support for the ``OffchainLookup`` revert / CCIP Read support. In order to properly handle a
1094+
call to a contract function that reverts with an ``OffchainLookup`` error for offchain data retrieval, the
1095+
``ccip_read_enabled`` flag has been added to the ``eth_call`` method. ``ccip_read_enabled`` is set to ``True`` by
1096+
default for calls, as recommended in `EIP-3668 <https://eips.ethereum.org/EIPS/eip-3668>`_, thus calls to contract
1097+
functions that revert with an ``OffchainLookup`` will be handled appropriately by default. If the
1098+
``ccip_read_enabled`` flag is set to ``False``, the call will raise the ``OffchainLookup`` instead of properly
1099+
handling the exception according to EIP-3668.
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10931101

10941102
.. py:method:: Eth.fee_history(block_count, newest_block, reward_percentiles=None)
10951103

‎tests/core/contracts/test_offchain_lookup.py

+3-3
Original file line numberDiff line numberDiff line change
@@ -12,13 +12,13 @@
1212
from web3._utils.module_testing.utils import (
1313
mock_offchain_lookup_request_response,
1414
)
15-
from web3._utils.type_conversion_utils import (
16-
to_hex_if_bytes,
17-
)
1815
from web3.exceptions import (
1916
TooManyRequests,
2017
ValidationError,
2118
)
19+
from web3.utils import (
20+
to_hex_if_bytes,
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)
2222

2323
# "test offchain lookup" as an abi-encoded string
2424
OFFCHAIN_LOOKUP_TEST_DATA = '0x0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000001474657374206f6666636861696e206c6f6f6b7570000000000000000000000000' # noqa: E501

‎tests/core/web3-module/test_providers.py

+1-2
Original file line numberDiff line numberDiff line change
@@ -25,6 +25,5 @@ def test_auto_provider_none():
2525
type(w3.provider) == AutoProvider
2626

2727

28-
def test_provider_default_values_for_ccip_read(w3):
29-
assert w3.provider.ccip_read_enabled
28+
def test_provider_default_value_for_ccip_read_redirect(w3):
3029
assert w3.provider.ccip_read_max_redirects == 4

‎tests/ens/test_offchain_resolution.py

+8-32
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,5 @@
11
import pytest
22

3-
from eth_abi.abi import (
4-
decode_abi,
5-
)
6-
from eth_utils import (
7-
to_checksum_address,
8-
)
93
import requests
104

115
from ens.utils import (
@@ -113,37 +107,19 @@ def mock_get(*args, **_):
113107
ens.address('offchainexample.eth')
114108

115109

116-
def test_offchain_resolver_function_call_with_ccip_read_enabled(ens, monkeypatch):
117-
def mock_get(*args, **kwargs):
118-
return MockHttpSuccessResponse('get', *args, **kwargs)
119-
120-
monkeypatch.setattr(requests.Session, 'get', mock_get)
121-
110+
def test_offchain_resolver_function_call_raises_with_ccip_read_disabled(ens, monkeypatch):
122111
offchain_resolver = ens.resolver('offchainexample.eth')
123112

124-
# set global ccip_read_enabled flag on provider to False
125-
ens.w3.provider.ccip_read_enabled = False
126-
127-
# should fail here with global provider flag set to False
113+
# should fail here with `ccip_read_enabled` flag set to False
128114
with pytest.raises(OffchainLookup):
129115
offchain_resolver.functions.resolve(
130116
ens_encode_name('offchainexample.eth'),
131117
ENCODED_ADDR_CALLDATA,
132-
).call()
133-
134-
# pass flag on specific call should work
135-
resolved_via_function_call = offchain_resolver.functions.resolve(
136-
ens_encode_name('offchainexample.eth'),
137-
ENCODED_ADDR_CALLDATA,
138-
).call(ccip_read_enabled=True)
118+
).call(ccip_read_enabled=False)
139119

140120
# pass flag on specific call via ContractCaller is also an option
141-
resolved_via_caller = offchain_resolver.caller(ccip_read_enabled=True).resolve(
142-
ens_encode_name('offchainexample.eth'),
143-
ENCODED_ADDR_CALLDATA,
144-
)
145-
146-
assert resolved_via_caller == resolved_via_function_call
147-
148-
decoded_result = decode_abi(['address'], resolved_via_caller)[0]
149-
assert to_checksum_address(decoded_result) == EXPECTED_RESOLVED_ADDRESS
121+
with pytest.raises(OffchainLookup):
122+
offchain_resolver.caller(ccip_read_enabled=False).resolve(
123+
ens_encode_name('offchainexample.eth'),
124+
ENCODED_ADDR_CALLDATA,
125+
)

‎web3/_utils/async_transactions.py

-85
Original file line numberDiff line numberDiff line change
@@ -1,30 +1,9 @@
11
from typing import (
22
TYPE_CHECKING,
3-
Any,
4-
Dict,
53
Optional,
64
cast,
75
)
86

9-
from eth_abi import (
10-
encode_abi,
11-
)
12-
from eth_typing import (
13-
URI,
14-
)
15-
16-
from web3._utils.request import (
17-
async_get_json_from_client_response,
18-
async_get_response_from_get_request,
19-
async_get_response_from_post_request,
20-
)
21-
from web3._utils.type_conversion_utils import (
22-
to_bytes_if_hex,
23-
to_hex_if_bytes,
24-
)
25-
from web3.exceptions import (
26-
ValidationError,
27-
)
287
from web3.types import (
298
BlockIdentifier,
309
TxParams,
@@ -61,67 +40,3 @@ async def get_buffered_gas_estimate(
6140
)
6241

6342
return min(gas_limit, gas_estimate + gas_buffer)
64-
65-
66-
async def async_handle_offchain_lookup(
67-
offchain_lookup_payload: Dict[str, Any],
68-
transaction: TxParams,
69-
) -> bytes:
70-
formatted_sender = to_hex_if_bytes(offchain_lookup_payload['sender']).lower()
71-
formatted_data = to_hex_if_bytes(offchain_lookup_payload['callData']).lower()
72-
73-
if formatted_sender != to_hex_if_bytes(transaction['to']).lower():
74-
raise ValidationError(
75-
'Cannot handle OffchainLookup raised inside nested call. Returned `sender` '
76-
'value does not equal `to` address in transaction.'
77-
)
78-
79-
for url in offchain_lookup_payload['urls']:
80-
formatted_url = URI(
81-
str(url)
82-
.replace('{sender}', str(formatted_sender))
83-
.replace('{data}', str(formatted_data))
84-
)
85-
86-
try:
87-
if '{data}' in url and '{sender}' in url:
88-
response = await async_get_response_from_get_request(formatted_url)
89-
elif '{sender}' in url:
90-
response = await async_get_response_from_post_request(formatted_url, data={
91-
"data": formatted_data,
92-
"sender": formatted_sender
93-
})
94-
else:
95-
raise ValidationError('url not formatted properly.')
96-
except Exception:
97-
continue # try next url if timeout or issues making the request
98-
99-
if 400 <= response.status <= 499: # if request returns 400 error, raise exception
100-
response.raise_for_status()
101-
if not 200 <= response.status <= 299: # if not 400 error, try next url
102-
continue
103-
104-
result = await async_get_json_from_client_response(response)
105-
106-
if 'data' not in result.keys():
107-
raise ValidationError(
108-
"Improperly formatted response for offchain lookup HTTP request - missing 'data' "
109-
"field."
110-
)
111-
112-
encoded_data_with_function_selector = b''.join([
113-
# 4-byte callback function selector
114-
to_bytes_if_hex(offchain_lookup_payload['callbackFunction']),
115-
116-
# encode the `data` from the result and the `extraData` as bytes
117-
encode_abi(
118-
['bytes', 'bytes'],
119-
[
120-
to_bytes_if_hex(result['data']),
121-
to_bytes_if_hex(offchain_lookup_payload['extraData']),
122-
]
123-
)
124-
])
125-
126-
return encoded_data_with_function_selector
127-
raise Exception("Offchain lookup failed for supplied urls.")

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