v5 backport - Add chain_id setter

newsfragments/2207.feature.rst

@@ -0,0 +1 @@
+Add setter for the Eth.chain_id property

tests/core/eth-module/test_eth_properties.py

@@ -1,8 +1,27 @@
 import pytest
 
+from web3 import Web3
+from web3.eth import (
+    AsyncEth,
+)
+from web3.providers.eth_tester.main import (
+    AsyncEthereumTesterProvider,
+)
+
+
+@pytest.fixture
+def async_w3():
+    return Web3(
+        AsyncEthereumTesterProvider(),
+        middlewares=[],
+        modules={
+            'eth': (AsyncEth,),
+        })
+
 
 def test_eth_protocol_version(web3):
-    assert web3.eth.protocol_version == '63'
+    with pytest.warns(DeprecationWarning):
+        assert web3.eth.protocol_version == '63'
 
 
 def test_eth_protocolVersion(web3):
@@ -17,3 +36,24 @@ def test_eth_chain_id(web3):
 def test_eth_chainId(web3):
     with pytest.warns(DeprecationWarning):
         assert web3.eth.chainId == 61
+
+
+def test_set_chain_id(web3):
+    assert web3.eth.chain_id == 61
+
+    web3.eth.chain_id = 72
+    assert web3.eth.chain_id == 72
+
+    web3.eth.chain_id = None
+    assert web3.eth.chain_id == 61
+
+
+@pytest.mark.asyncio
+async def test_async_set_chain_id(async_w3):
+    assert await async_w3.eth.chain_id == 61
+
+    async_w3.eth.chain_id = 72
+    assert await async_w3.eth.chain_id == 72
+
+    async_w3.eth.chain_id = None
+    assert await async_w3.eth.chain_id == 61

web3/eth.py

@@ -114,6 +114,7 @@
 class BaseEth(Module):
     _default_account: Union[ChecksumAddress, Empty] = empty
     _default_block: BlockIdentifier = "latest"
+    _default_chain_id: Optional[int] = None
     gasPriceStrategy = None
 
     _gas_price: Method[Callable[[], Wei]] = Method(
@@ -357,7 +358,14 @@ async def block_number(self) -> BlockNumber:
 
     @property
     async def chain_id(self) -> int:
-        return await self._chain_id()  # type: ignore
+        if self._default_chain_id is None:
+            return await self._chain_id()  # type: ignore
+        else:
+            return self._default_chain_id
+
+    @chain_id.setter
+    def chain_id(self, value: int) -> None:
+        self._default_chain_id = value
 
     @property
     async def coinbase(self) -> ChecksumAddress:
@@ -629,7 +637,14 @@ def blockNumber(self) -> BlockNumber:
 
     @property
     def chain_id(self) -> int:
-        return self._chain_id()
+        if self._default_chain_id is None:
+            return self._chain_id()
+        else:
+            return self._default_chain_id
+
+    @chain_id.setter
+    def chain_id(self, value: int) -> None:
+        self._default_chain_id = value
 
     @property
     def chainId(self) -> int: