Fix incorrect raising of IndexError in RPC

Previously due to the fact that the type of error returned by Bitcoin core
wasn't checked, errors unrelated to missing blocks and txs would result in
false IndexErrors instead.

Additionally, this commit adds some useful subclasses for some of the different
types of RPC errors.

Author: petertodd

bitcoin/rpc.py

@@ -60,14 +60,61 @@
 
 
 class JSONRPCError(Exception):
-    """JSON-RPC protocol error"""
+    """JSON-RPC protocol error base class
+
+    Subclasses of this class also exist for specific types of errors; the set
+    of all subclasses is by no means complete.
+    """
+
+    SUBCLS_BY_CODE = {}
+
+    @classmethod
+    def _register_subcls(cls, subcls):
+        cls.SUBCLS_BY_CODE[subcls.RPC_ERROR_CODE] = subcls
+        return subcls
+
+    def __new__(cls, rpc_error):
+        assert cls is JSONRPCError
+        cls = JSONRPCError.SUBCLS_BY_CODE.get(rpc_error['code'], cls)
+
+        self = Exception.__new__(cls)
 
-    def __init__(self, rpc_error):
         super(JSONRPCError, self).__init__(
             'msg: %r  code: %r' %
             (rpc_error['message'], rpc_error['code']))
         self.error = rpc_error
 
+        return self
+
+@JSONRPCError._register_subcls
+class ForbiddenBySafeModeError(JSONRPCError):
+    RPC_ERROR_CODE = -2
+
+@JSONRPCError._register_subcls
+class InvalidAddressOrKeyError(JSONRPCError):
+    RPC_ERROR_CODE = -5
+
+@JSONRPCError._register_subcls
+class InvalidParameterError(JSONRPCError):
+    RPC_ERROR_CODE = -8
+
+@JSONRPCError._register_subcls
+class VerifyError(JSONRPCError):
+    RPC_ERROR_CODE = -25
+
+@JSONRPCError._register_subcls
+class VerifyRejectedError(JSONRPCError):
+    RPC_ERROR_CODE = -26
+
+@JSONRPCError._register_subcls
+class VerifyAlreadyInChainError(JSONRPCError):
+    RPC_ERROR_CODE = -27
+
+@JSONRPCError._register_subcls
+class InWarmupError(JSONRPCError):
+    RPC_ERROR_CODE = -28
+
+
 class BaseProxy(object):
     """Base JSON-RPC proxy class. Contains only private methods; do not use
     directly."""
@@ -335,7 +382,7 @@ def getblockheader(self, block_hash, verbose=False):
                     (self.__class__.__name__, block_hash.__class__))
         try:
             r = self._call('getblockheader', block_hash, verbose)
-        except JSONRPCError as ex:
+        except InvalidAddressOrKeyError as ex:
             raise IndexError('%s.getblockheader(): %s (%d)' %
                     (self.__class__.__name__, ex.error['message'], ex.error['code']))
 
@@ -364,7 +411,7 @@ def getblock(self, block_hash):
                     (self.__class__.__name__, block_hash.__class__))
         try:
             r = self._call('getblock', block_hash, False)
-        except JSONRPCError as ex:
+        except InvalidAddressOrKeyError as ex:
             raise IndexError('%s.getblock(): %s (%d)' %
                     (self.__class__.__name__, ex.error['message'], ex.error['code']))
         return CBlock.deserialize(unhexlify(r))
@@ -380,7 +427,7 @@ def getblockhash(self, height):
         """
         try:
             return lx(self._call('getblockhash', height))
-        except JSONRPCError as ex:
+        except InvalidParameterError as ex:
             raise IndexError('%s.getblockhash(): %s (%d)' %
                     (self.__class__.__name__, ex.error['message'], ex.error['code']))
 
@@ -442,7 +489,7 @@ def getrawtransaction(self, txid, verbose=False):
         """
         try:
             r = self._call('getrawtransaction', b2lx(txid), 1 if verbose else 0)
-        except JSONRPCError as ex:
+        except InvalidAddressOrKeyError as ex:
             raise IndexError('%s.getrawtransaction(): %s (%d)' %
                     (self.__class__.__name__, ex.error['message'], ex.error['code']))
         if verbose:
@@ -485,7 +532,7 @@ def gettransaction(self, txid):
         """
         try:
             r = self._call('gettransaction', b2lx(txid))
-        except JSONRPCError as ex:
+        except InvalidAddressOrKeyError as ex:
             raise IndexError('%s.getrawtransaction(): %s (%d)' %
                     (self.__class__.__name__, ex.error['message'], ex.error['code']))
         return r
@@ -622,6 +669,13 @@ def removenode(self, node):
 
 __all__ = (
     'JSONRPCError',
+    'ForbiddenBySafeModeError',
+    'InvalidAddressOrKeyError',
+    'InvalidParameterError',
+    'VerifyError',
+    'VerifyRejectedError',
+    'VerifyAlreadyInChainError',
+    'InWarmupError',
     'RawProxy',
     'Proxy',
 )

release-notes.md

@@ -12,6 +12,14 @@ Breaking API changes:
 * The alias `JSONRPCException = JSONRPCError` has been removed. This alias was
   added for compatibility with v0.4.0 of python-bitcoinlib.
 
+* Where appropriate, `RPC_INVALID_ADDRESS_OR_KEY` errors are now caught
+  properly, which means that rather than raising `IndexError`, RPC commands
+  such as `getblock` may raise `JSONRPCError` instead. For instance during
+  initial startup previously python-bitcoinlib would incorrectly raise
+  `IndexError` rather than letting the callee know that RPC was unusable. Along
+  those lines, `JSONRPCError` subclasses have been added for some (but not
+  all!) of the types of RPC errors Bitcoin Core returns.
+
 Bugfixes:
 
 * Fixed a spurious `AttributeError` when `bitcoin.rpc.Proxy()` fails.