Use a consistent effective gas price lookup in VM

Author: carver

eth/vm/forks/frontier/state.py

@@ -50,8 +50,13 @@ def validate_transaction(self, transaction: SignedTransactionAPI) -> None:
         self.vm_state.validate_transaction(transaction)
 
     def build_evm_message(self, transaction: SignedTransactionAPI) -> MessageAPI:
-
-        gas_fee = transaction.gas * transaction.gas_price
+        # Use vm_state.get_gas_price instead of transaction_context.gas_price so
+        #   that we can run get_transaction_result (aka~ eth_call) and estimate_gas.
+        #   Both work better if the GASPRICE opcode returns the original real price,
+        #   but the sender's balance doesn't actually deduct the gas. This get_gas_price()
+        #   will return 0 for eth_call, but transaction_context.gas_price will return
+        #   the same value as the GASPRICE opcode.
+        gas_fee = transaction.gas * self.vm_state.get_gas_price(transaction)
 
         # Buy Gas
         self.vm_state.delta_balance(transaction.sender, -1 * gas_fee)

eth/vm/forks/london/state.py

@@ -39,10 +39,13 @@
 
 
 class LondonTransactionExecutor(BerlinTransactionExecutor):
-    def build_evm_message(
-        self,
-        transaction: SignedTransactionAPI,
-    ) -> MessageAPI:
+    def build_evm_message(self, transaction: SignedTransactionAPI) -> MessageAPI:
+        # Use vm_state.get_gas_price instead of transaction_context.gas_price so
+        #   that we can run get_transaction_result (aka~ eth_call) and estimate_gas.
+        #   Both work better if the GASPRICE opcode returns the original real price,
+        #   but the sender's balance doesn't actually deduct the gas. This get_gas_price()
+        #   will return 0 for eth_call, but transaction_context.gas_price will return
+        #   the same value as the GASPRICE opcode.
         gas_fee = transaction.gas * self.vm_state.get_gas_price(transaction)
 
         # Buy Gas

eth/vm/state.py

@@ -89,12 +89,17 @@ def gas_limit(self) -> int:
         return self.execution_context.gas_limit
 
     def get_gas_price(self, transaction: SignedTransactionAPI) -> int:
-        base_gas_price = self.execution_context.base_fee_per_gas
-        priority_fee_per_gas = min(
-            transaction.max_priority_fee_per_gas,
-            transaction.max_fee_per_gas - base_gas_price,
-        )
-        return priority_fee_per_gas + base_gas_price
+        execution_context = self.execution_context
+        try:
+            base_gas_price = execution_context.base_fee_per_gas
+        except AttributeError:
+            return transaction.gas_price
+        else:
+            effective_price = min(
+                transaction.max_fee_per_gas,
+                transaction.max_priority_fee_per_gas + base_gas_price,
+            )
+            return effective_price
 
     #
     # Access to account db