Housekeeping; expose consensus type (closes #679)

src/ethereum/fork_criteria.py

@@ -14,7 +14,7 @@
 
 import functools
 from abc import ABC, abstractmethod
-from typing import Tuple
+from typing import Final, Tuple
 
 
 # MyPy doesn't support decorators on abstract classes
@@ -25,9 +25,9 @@ class ForkCriteria(ABC):
     Type that represents the condition required for a fork to occur.
     """
 
-    BLOCK_NUMBER = 0
-    TIMESTAMP = 1
-    UNSCHEDULED = 2
+    BLOCK_NUMBER: Final[int] = 0
+    TIMESTAMP: Final[int] = 1
+    UNSCHEDULED: Final[int] = 2
 
     _internal: Tuple[int, int]
 
@@ -61,6 +61,13 @@ def check(self, block_number: int, timestamp: int) -> bool:
         """
         ...
 
+    @abstractmethod
+    def __repr__(self) -> str:
+        """
+        String representation of this object.
+        """
+        raise NotImplementedError()
+
 
 class ByBlockNumber(ForkCriteria):
     """
@@ -79,6 +86,12 @@ def check(self, block_number: int, timestamp: int) -> bool:
         """
         return block_number >= self.block_number
 
+    def __repr__(self) -> str:
+        """
+        String representation of this object.
+        """
+        return f"ByBlockNumber({self.block_number})"
+
 
 class ByTimestamp(ForkCriteria):
     """
@@ -97,6 +110,12 @@ def check(self, block_number: int, timestamp: int) -> bool:
         """
         return timestamp >= self.timestamp
 
+    def __repr__(self) -> str:
+        """
+        String representation of this object.
+        """
+        return f"ByTimestamp({self.timestamp})"
+
 
 class Unscheduled(ForkCriteria):
     """
@@ -111,3 +130,9 @@ def check(self, block_number: int, timestamp: int) -> bool:
         Unscheduled forks never occur.
         """
         return False
+
+    def __repr__(self) -> str:
+        """
+        String representation of this object.
+        """
+        return "Unscheduled()"

src/ethereum_spec_tools/evm_tools/fixture_loader.py

@@ -149,13 +149,10 @@ def network(self) -> str:
     def proof_of_stake(self) -> bool:
         """Whether the fork is proof of stake"""
         forks = Hardfork.discover()
-        merge_fork_found = False
         for fork in forks:
-            if fork.name == "ethereum.paris":
-                merge_fork_found = True
             if fork.name == "ethereum." + self._fork_module:
-                break
-        return merge_fork_found
+                return fork.consensus.is_pos()
+        raise Exception(f"fork {self._fork_module} not discovered")
 
     @property
     def Block(self) -> Any:

src/ethereum_spec_tools/forks.py

@@ -7,13 +7,36 @@
 
 import importlib
 import pkgutil
+from enum import Enum, auto
 from pkgutil import ModuleInfo
 from types import ModuleType
 from typing import Any, Dict, Iterator, List, Optional, Type, TypeVar
 
 import ethereum
 from ethereum.fork_criteria import ByBlockNumber, ByTimestamp, ForkCriteria
 
+
+class ConsensusType(Enum):
+    """
+    How a fork chooses its canonical chain.
+    """
+
+    PROOF_OF_WORK = auto()
+    PROOF_OF_STAKE = auto()
+
+    def is_pow(self) -> bool:
+        """
+        Returns True if self == PROOF_OF_WORK.
+        """
+        return self == ConsensusType.PROOF_OF_WORK
+
+    def is_pos(self) -> bool:
+        """
+        Returns True if self == PROOF_OF_STAKE.
+        """
+        return self == ConsensusType.PROOF_OF_STAKE
+
+
 H = TypeVar("H", bound="Hardfork")
 
 
@@ -98,12 +121,24 @@ def load_from_json(cls: Type[H], json: Any) -> List[H]:
     def __init__(self, mod: ModuleType) -> None:
         self.mod = mod
 
+    @property
+    def consensus(self) -> ConsensusType:
+        """
+        How this fork chooses its canonical chain.
+        """
+        if hasattr(self.module("fork"), "validate_proof_of_work"):
+            return ConsensusType.PROOF_OF_WORK
+        else:
+            return ConsensusType.PROOF_OF_STAKE
+
     @property
     def criteria(self) -> ForkCriteria:
         """
         Criteria to trigger this hardfork.
         """
-        return self.mod.FORK_CRITERIA  # type: ignore
+        criteria = self.mod.FORK_CRITERIA  # type: ignore[attr-defined]
+        assert isinstance(criteria, ForkCriteria)
+        return criteria
 
     @property
     def block(self) -> int:
@@ -167,7 +202,7 @@ def __repr__(self) -> str:
             self.__class__.__name__
             + "("
             + f"name={self.name!r}, "
-            + f"block={self.block}, "
+            + f"criteria={self.criteria}, "
             + "..."
             + ")"
         )