Implement eth_chainId endpoint

docs/web3.eth.rst

@@ -153,6 +153,18 @@ The following properties are available on the ``web3.eth`` namespace.
        '63'
 
 
+.. py:attribute:: Eth.chainId
+
+    * Delegates to ``eth_chainId`` RPC Method
+
+    Returns a hex-encoded integer value for the currently configured "Chain Id" value introduced in `EIP-155 <https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md>`_. Returns ``None`` if no Chain Id is available.
+
+    .. code-block:: python
+
+       >>> web3.eth.chainId
+       '0x3d'
+
+
 Methods
 -------
 

tests/core/eth-module/test_eth_protocolVersion.py → tests/core/eth-module/test_eth_properties.py

@@ -1,2 +1,6 @@
 def test_eth_protocolVersion(web3):
     assert web3.eth.protocolVersion == '63'
+
+
+def test_eth_chainId(web3):
+    assert web3.eth.chainId == '0x3d'

tests/integration/go_ethereum/common.py

@@ -65,6 +65,11 @@ def test_eth_submitHashrate(self, web3):
             pytest.xfail('eth_submitHashrate depracated in 1.8.22 for ethash_submitHashRate')
         super().test_eth_submitHashrate(web3)
 
+    def test_eth_chainId(self, web3):
+        if 'v1.7.2' in web3.clientVersion:
+            pytest.xfail('eth_chainId not implemented in geth 1.7.2')
+        super().test_eth_chainId(web3)
+
 
 class GoEthereumVersionModuleTest(VersionModuleTest):
     pass

tests/integration/parity/common.py

@@ -24,6 +24,11 @@ def _check_web3_clientVersion(self, client_version):
 
 
 class ParityEthModuleTest(EthModuleTest):
+    def test_eth_chainId(self, web3):
+        # Parity will return null if chainId is not available
+        chain_id = web3.eth.chainId
+        assert chain_id is None
+
     def test_eth_getBlockByNumber_pending(self, web3):
         pytest.xfail('Parity dropped "pending" option in 1.11.1')
         super().test_eth_getBlockByNumber_pending(web3)

tests/integration/test_ethereum_tester.py

@@ -7,9 +7,13 @@
 from eth_utils import (
     is_checksum_address,
     is_dict,
+    is_hex,
 )
 
 from web3 import Web3
+from web3._utils.formatters import (
+    hex_to_integer,
+)
 from web3._utils.module_testing import (
     EthModuleTest,
     GoEthereumPersonalModuleTest,
@@ -291,6 +295,11 @@ def test_eth_estimateGas_with_block(self,
             web3, unlocked_account_dual_type
         )
 
+    def test_eth_chainId(self, web3):
+        chain_id = web3.eth.chainId
+        assert is_hex(chain_id)
+        assert hex_to_integer(chain_id) is 61
+
 
 class TestEthereumTesterVersionModule(VersionModuleTest):
     pass

web3/_utils/module_testing/eth_module.py

@@ -14,6 +14,7 @@
     is_list_like,
     is_same_address,
     is_string,
+    to_int,
 )
 from hexbytes import (
     HexBytes,
@@ -65,6 +66,11 @@ def test_eth_hashrate(self, web3):
         assert is_integer(hashrate)
         assert hashrate >= 0
 
+    def test_eth_chainId(self, web3):
+        chain_id = web3.eth.chainId
+        # chain id value from geth fixture genesis file
+        assert to_int(hexstr=chain_id) == 131277322940537
+
     def test_eth_gasPrice(self, web3):
         gas_price = web3.eth.gasPrice
         assert is_integer(gas_price)

web3/eth.py

@@ -101,6 +101,10 @@ def accounts(self):
     def blockNumber(self):
         return self.web3.manager.request_blocking("eth_blockNumber", [])
 
+    @property
+    def chainId(self):
+        return self.web3.manager.request_blocking("eth_chainId", [])
+
     def getBalance(self, account, block_identifier=None):
         if block_identifier is None:
             block_identifier = self.defaultBlock

web3/providers/eth_tester/defaults.py

@@ -170,6 +170,7 @@ def personal_send_transaction(eth_tester, params):
         ),
         'mining': static_return(False),
         'hashrate': static_return(0),
+        'chainId': static_return('0x3d'),
         'gasPrice': static_return(1),
         'accounts': call_eth_tester('get_accounts'),
         'blockNumber': compose(