lint: ignore W503 instead of W504 (line break before/after binary ope…

…rator).

PEP8 says it's nicer to have line breaks before binary operators:

> Following the tradition from mathematics usually results in
> more readable code:
> ...

eth/_utils/transactions.py

@@ -136,8 +136,8 @@ def calculate_intrinsic_gas(
     else:
         create_cost = 0
     return (
-        gas_schedule.gas_tx +
-        num_zero_bytes * gas_schedule.gas_txdatazero +
-        num_non_zero_bytes * gas_schedule.gas_txdatanonzero +
-        create_cost
+        gas_schedule.gas_tx
+        + num_zero_bytes * gas_schedule.gas_txdatazero
+        + num_non_zero_bytes * gas_schedule.gas_txdatanonzero
+        + create_cost
     )

eth/consensus/clique/snapshot_manager.py

@@ -225,16 +225,16 @@ def get_snapshot(self, block_number: int, block_hash: Hash32) -> Snapshot:
                 # Otherwise, we can retrieve it on the fly
                 header = self._chain_db.get_block_header_by_hash(block_hash)
             except HeaderNotFound:
-                raise SnapshotNotFound(f"Can not get snapshot for {block_hash!r} at {block_number}")
+                raise SnapshotNotFound(f"Can not get snapshot for {block_hash} at {block_number}")
             else:
                 if header.block_number != block_number:
                     raise SnapshotNotFound(
-                        f"Can not get snapshot for {block_hash!r} at {block_number}"
+                        f"Can not get snapshot for {block_hash} at {block_number}"
                     )
                 else:
                     return self._create_snapshot_from_checkpoint_header(header)
 
-        raise SnapshotNotFound(f"Can not get snapshot for {block_hash!r} at {block_number}")
+        raise SnapshotNotFound(f"Can not get snapshot for {block_hash} at {block_number}")
 
     def add_snapshot(self, mutable_snapshot: MutableSnapshot) -> Snapshot:
         """
@@ -261,8 +261,8 @@ def get_snapshot_from_db(self, block_hash: Hash32) -> Snapshot:
             encoded_key = self._chain_db.db[key]
         except KeyError as e:
             raise SnapshotNotFound(
-                f"Can not get on-disk snapshot for {block_hash!r}"
-            ) from e
+                f"Can not get on-disk snapshot for {block_hash}"
+            )
         else:
             return decode_snapshot(encoded_key)
 

eth/precompiles/modexp.py

@@ -34,8 +34,8 @@ def _compute_adjusted_exponent_length(exponent_length: int,
     else:
         first_32_bytes_as_int = big_endian_to_int(first_32_exponent_bytes)
         return (
-            8 * (exponent_length - 32) +
-            get_highest_bit_index(first_32_bytes_as_int)
+            8 * (exponent_length - 32)
+            + get_highest_bit_index(first_32_bytes_as_int)
         )
 
 
@@ -78,9 +78,9 @@ def _compute_modexp_gas_fee(data: bytes) -> int:
     complexity = _compute_complexity(max(modulus_length, base_length))
 
     gas_fee = (
-        complexity *
-        max(adjusted_exponent_length, 1) //
-        constants.GAS_MOD_EXP_QUADRATIC_DENOMINATOR
+        complexity
+        * max(adjusted_exponent_length, 1)
+        // constants.GAS_MOD_EXP_QUADRATIC_DENOMINATOR
     )
     return gas_fee
 

eth/vm/forks/byzantium/headers.py

@@ -50,8 +50,8 @@ def compute_difficulty(
     has_uncles = parent_header.uncles_hash != EMPTY_UNCLE_HASH
     adj_factor = max(
         (
-            (2 if has_uncles else 1) -
-            ((timestamp - parent_timestamp) // BYZANTIUM_DIFFICULTY_ADJUSTMENT_CUTOFF)
+            (2 if has_uncles else 1)
+            - ((timestamp - parent_timestamp) // BYZANTIUM_DIFFICULTY_ADJUSTMENT_CUTOFF)
         ),
         -99,
     )

eth/vm/forks/spurious_dragon/state.py

@@ -31,8 +31,8 @@ def finalize_computation(self,
 
         for account in touched_accounts:
             should_delete = (
-                self.vm_state.account_exists(account) and
-                self.vm_state.account_is_empty(account)
+                self.vm_state.account_exists(account)
+                and self.vm_state.account_is_empty(account)
             )
             if should_delete:
                 self.vm_state.logger.debug2(

eth/vm/logic/call.py

@@ -365,8 +365,8 @@ def compute_msg_extra_gas(self,
                               to: Address,
                               value: int) -> int:
         account_is_dead = (
-            not computation.state.account_exists(to) or
-            computation.state.account_is_empty(to)
+            not computation.state.account_exists(to)
+            or computation.state.account_is_empty(to)
         )
 
         transfer_gas_fee = constants.GAS_CALLVALUE if value else 0

eth/vm/logic/system.py

@@ -65,8 +65,8 @@ def selfdestruct_eip150(computation: ComputationAPI) -> None:
 def selfdestruct_eip161(computation: ComputationAPI) -> None:
     beneficiary = force_bytes_to_address(computation.stack_pop1_bytes())
     is_dead = (
-        not computation.state.account_exists(beneficiary) or
-        computation.state.account_is_empty(beneficiary)
+        not computation.state.account_exists(beneficiary)
+        or computation.state.account_is_empty(beneficiary)
     )
     if is_dead and computation.state.get_balance(computation.msg.storage_address):
         computation.consume_gas(

eth/vm/state.py

@@ -188,9 +188,9 @@ def persist(self) -> MetaWitnessAPI:
     def get_ancestor_hash(self, block_number: int) -> Hash32:
         ancestor_depth = self.block_number - block_number - 1
         is_ancestor_depth_out_of_range = (
-            ancestor_depth >= MAX_PREV_HEADER_DEPTH or
-            ancestor_depth < 0 or
-            block_number < 0
+            ancestor_depth >= MAX_PREV_HEADER_DEPTH
+            or ancestor_depth < 0
+            or block_number < 0
         )
         if is_ancestor_depth_out_of_range:
             return Hash32(b'')

tests/core/vm/test_rewards.py

@@ -78,9 +78,9 @@ def test_rewards(vm_fn, miner_1_balance, miner_2_balance):
 
     # We first test if the balance matches what we would determine
     # if we made all the API calls involved ourselves.
-    assert coinbase_balance == (vm.get_block_reward() *
-                                TOTAL_BLOCKS_CANONICAL_CHAIN +
-                                vm.get_nephew_reward())
+    assert coinbase_balance == (vm.get_block_reward()
+                                * TOTAL_BLOCKS_CANONICAL_CHAIN
+                                + vm.get_nephew_reward())
     assert other_miner_balance == vm.get_uncle_reward(block.number, uncle)
 
     # But we also ensure the balance matches the numbers that we calculated on paper
@@ -181,9 +181,9 @@ def test_rewards_uncle_created_at_different_generations(
 
     # We first test if the balance matches what we would determine
     # if we made all the API calls involved ourselves.
-    assert coinbase_balance == (vm.get_block_reward() *
-                                TOTAL_BLOCKS_CANONICAL_CHAIN +
-                                vm.get_nephew_reward())
+    assert coinbase_balance == (vm.get_block_reward()
+                                * TOTAL_BLOCKS_CANONICAL_CHAIN
+                                + vm.get_nephew_reward())
 
     assert other_miner_balance == vm.get_uncle_reward(block.number, uncle)
 
@@ -298,9 +298,9 @@ def test_rewards_nephew_uncle_different_vm(
     # We first test if the balance matches what we would determine
     # if we made all the API calls involved ourselves.
     assert coinbase_balance == (
-        uncle_vm.get_block_reward() * 3 +
-        nephew_vm.get_block_reward() * (TOTAL_BLOCKS_CANONICAL_CHAIN - 3) +
-        vm.get_nephew_reward()
+        uncle_vm.get_block_reward() * 3
+        + nephew_vm.get_block_reward() * (TOTAL_BLOCKS_CANONICAL_CHAIN - 3)
+        + vm.get_nephew_reward()
     )
     assert other_miner_balance == vm.get_uncle_reward(block.number, uncle)
 

tox.ini

@@ -13,9 +13,11 @@ ignore =
     # E252 missing whitespace around parameter equals
     # Already used too much in the codebase at the point of introduction.
     E252,
-    # W504 line break after binary operator
-    # It's either this or W503 (line break _before_ binary operator), pick your poison
-    W504
+    # W503 line break before binary operator
+    # It's either this or W504 (line break _after_ binary operator), pick your poison.
+    # W503 gets enabled when E252 gets ignored, see:
+    # https://github.com/ethereum/py-evm/pull/1940#discussion_r432606845
+    W503
 
 [testenv]
 usedevelop=True