Return correct error codes in blockchain.cpp.

RPCs in blockchain.cpp were returning misleading or incorrect error
codes (for example getblock() returning RPC_INTERNAL_ERROR when the
block had been pruned). This commit fixes those error codes:

- RPC_INTERNAL_ERROR should not be returned for application-level
  errors, only for genuine internal errors such as corrupted data.
- RPC_METHOD_NOT_FOUND should not be returned in response to a
  JSON request for an existing method.

Those error codes have been replaced with RPC_MISC_ERROR or
RPC_INVALID_PARAMETER as appropriate.

1 files changed, 11 insertions, 6 deletions

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 24ced1a819..43eec9a1fb 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -745,10 +745,15 @@ UniValue getblock(const JSONRPCRequest& request)
     CBlockIndex* pblockindex = mapBlockIndex[hash];
 
     if (fHavePruned && !(pblockindex->nStatus & BLOCK_HAVE_DATA) && pblockindex->nTx > 0)
-        throw JSONRPCError(RPC_INTERNAL_ERROR, "Block not available (pruned data)");
+        throw JSONRPCError(RPC_MISC_ERROR, "Block not available (pruned data)");
 
-    if(!ReadBlockFromDisk(block, pblockindex, Params().GetConsensus()))
-        throw JSONRPCError(RPC_INTERNAL_ERROR, "Can't read block from disk");
+    if (!ReadBlockFromDisk(block, pblockindex, Params().GetConsensus()))
+        // Block not found on disk. This could be because we have the block
+        // header in our index but don't have the block (for example if a
+        // non-whitelisted node sends us an unrequested long chain of valid
+        // blocks, we add the headers to our index, but don't accept the
+        // block).
+        throw JSONRPCError(RPC_MISC_ERROR, "Block not found on disk");
 
     if (!fVerbose)
     {
@@ -830,7 +835,7 @@ UniValue pruneblockchain(const JSONRPCRequest& request)
             + HelpExampleRpc("pruneblockchain", "1000"));
 
     if (!fPruneMode)
-        throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Cannot prune blocks because node is not in prune mode.");
+        throw JSONRPCError(RPC_MISC_ERROR, "Cannot prune blocks because node is not in prune mode.");
 
     LOCK(cs_main);
 
@@ -844,7 +849,7 @@ UniValue pruneblockchain(const JSONRPCRequest& request)
         // Add a 2 hour buffer to include blocks which might have had old timestamps
         CBlockIndex* pindex = chainActive.FindEarliestAtLeast(heightParam - TIMESTAMP_WINDOW);
         if (!pindex) {
-            throw JSONRPCError(RPC_INTERNAL_ERROR, "Could not find block with at least the specified timestamp.");
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Could not find block with at least the specified timestamp.");
         }
         heightParam = pindex->nHeight;
     }
@@ -852,7 +857,7 @@ UniValue pruneblockchain(const JSONRPCRequest& request)
     unsigned int height = (unsigned int) heightParam;
     unsigned int chainHeight = (unsigned int) chainActive.Height();
     if (chainHeight < Params().PruneAfterHeight())
-        throw JSONRPCError(RPC_INTERNAL_ERROR, "Blockchain is too short for pruning.");
+        throw JSONRPCError(RPC_MISC_ERROR, "Blockchain is too short for pruning.");
     else if (height > chainHeight)
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Blockchain is shorter than the attempted prune height.");
     else if (height > chainHeight - MIN_BLOCKS_TO_KEEP) {