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.

qa/rpc-tests/p2p-acceptblock.py

@@ -197,11 +197,8 @@ class AcceptBlockTest(BitcoinTestFramework):
                 assert_equal(x['status'], "headers-only")
 
         # But this block should be accepted by node0 since it has more work.
-        try:
         self.nodes[0].getblock(blocks_h3[0].hash)
         print("Unrequested more-work block accepted from non-whitelisted peer")
-        except:
-            raise AssertionError("Unrequested more work block was not processed")
 
         # Node1 should have accepted and reorged.
         assert_equal(self.nodes[1].getblockcount(), 3)
@@ -225,26 +222,17 @@ class AcceptBlockTest(BitcoinTestFramework):
                 tips[j] = next_block
 
         time.sleep(2)
-        for x in all_blocks:
+        # Blocks 1-287 should be accepted, block 288 should be ignored because it's too far ahead
-            try:
+        for x in all_blocks[:-1]:
             self.nodes[0].getblock(x.hash)
-                if x == all_blocks[287]:
+        assert_raises_jsonrpc(-1, "Block not found on disk", self.nodes[0].getblock, all_blocks[-1].hash)
-                    raise AssertionError("Unrequested block too far-ahead should have been ignored")
-            except:
-                if x == all_blocks[287]:
-                    print("Unrequested block too far-ahead not processed")
-                else:
-                    raise AssertionError("Unrequested block with more work should have been accepted")
 
         headers_message.headers.pop() # Ensure the last block is unrequested
         white_node.send_message(headers_message) # Send headers leading to tip
         white_node.send_message(msg_block(tips[1]))  # Now deliver the tip
-        try:
         white_node.sync_with_ping()
         self.nodes[1].getblock(tips[1].hash)
         print("Unrequested block far ahead of tip accepted from whitelisted peer")
-        except:
-            raise AssertionError("Unrequested block from whitelisted peer not accepted")
 
         # 5. Test handling of unrequested block on the node that didn't process
         # Should still not be processed (even though it has a child that has more

qa/rpc-tests/pruning.py

@@ -184,10 +184,7 @@ class PruneTest(BitcoinTestFramework):
 
     def reorg_back(self):
         # Verify that a block on the old main chain fork has been pruned away
-        try:
+        assert_raises_jsonrpc(-1, "Block not available (pruned data)", self.nodes[2].getblock, self.forkhash)
-            self.nodes[2].getblock(self.forkhash)
-            raise AssertionError("Old block wasn't pruned so can't test redownload")
-        except JSONRPCException as e:
         print("Will need to redownload block",self.forkheight)
 
         # Verify that we have enough history to reorg back to the fork point
@@ -233,7 +230,7 @@ class PruneTest(BitcoinTestFramework):
         # at this point, node has 995 blocks and has not yet run in prune mode
         node = self.nodes[node_number] = start_node(node_number, self.options.tmpdir, ["-debug=0"], timewait=900)
         assert_equal(node.getblockcount(), 995)
-        assert_raises_message(JSONRPCException, "not in prune mode", node.pruneblockchain, 500)
+        assert_raises_jsonrpc(-1, "not in prune mode", node.pruneblockchain, 500)
         self.stop_node(node_number)
 
         # now re-start in manual pruning mode
@@ -265,14 +262,14 @@ class PruneTest(BitcoinTestFramework):
             return os.path.isfile(self.options.tmpdir + "/node{}/regtest/blocks/blk{:05}.dat".format(node_number, index))
 
         # should not prune because chain tip of node 3 (995) < PruneAfterHeight (1000)
-        assert_raises_message(JSONRPCException, "Blockchain is too short for pruning", node.pruneblockchain, height(500))
+        assert_raises_jsonrpc(-1, "Blockchain is too short for pruning", node.pruneblockchain, height(500))
 
         # mine 6 blocks so we are at height 1001 (i.e., above PruneAfterHeight)
         node.generate(6)
         assert_equal(node.getblockchaininfo()["blocks"], 1001)
 
         # negative heights should raise an exception
-        assert_raises_message(JSONRPCException, "Negative", node.pruneblockchain, -10)
+        assert_raises_jsonrpc(-8, "Negative", node.pruneblockchain, -10)
 
         # height=100 too low to prune first block file so this is a no-op
         prune(100)
@@ -318,12 +315,9 @@ class PruneTest(BitcoinTestFramework):
     def wallet_test(self):
         # check that the pruning node's wallet is still in good shape
         print("Stop and start pruning node to trigger wallet rescan")
-        try:
         self.stop_node(2)
         start_node(2, self.options.tmpdir, ["-debug=1","-prune=550"])
         print("Success")
-        except Exception as detail:
-            raise AssertionError("Wallet test: unable to re-start the pruning node")
 
         # check that wallet loads loads successfully when restarting a pruned node after IBD.
         # this was reported to fail in #7494.
@@ -331,12 +325,9 @@ class PruneTest(BitcoinTestFramework):
         connect_nodes(self.nodes[0], 5)
         nds = [self.nodes[0], self.nodes[5]]
         sync_blocks(nds, wait=5, timeout=300)
-        try:
         self.stop_node(5) #stop and start to trigger rescan
         start_node(5, self.options.tmpdir, ["-debug=1","-prune=550"])
         print ("Success")
-        except Exception as detail:
-            raise AssertionError("Wallet test: unable to re-start node5")
 
     def run_test(self):
         print("Warning! This test requires 4GB of disk space and takes over 30 mins (up to 2 hours)")

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()))
+    if (!ReadBlockFromDisk(block, pblockindex, Params().GetConsensus()))
-        throw JSONRPCError(RPC_INTERNAL_ERROR, "Can't read block from disk");
+        // 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) {