Re-adjust canonical head to parent of block to be inserted (#726)

* Re-adjust canonical head to parent of block to be inserted

why:
  of the failing tests that remain to be solved, 30 of those will succeed
  if the canonical database chain head is cleverly adjusted -- yes, it
  looks like a hack, indeed.

details:
  at the moment, this hack works for the non-hive tests only and is
  triggered by a boolean argument passed on to the chain.persistBlocks()
  method.

* Use parent instead of canonical head for block to be inserted

why:
  side chains need to be inserted typically somewhere before the
  canonical head.

details:
  the previous _hack_ was unnecessary and removed, it was inspired by
  some verification in persistBlocks() which explicitly referenced the
  canonical head (which now might or might not refer to the newly inserted
  header.)

* remove unnecessary code + comment

hive_integration/nodocker/consensus/consensus_sim.nim

@@ -8,8 +8,8 @@
 # those terms.
 
 import
-  std/[os, parseopt, json],
-  eth/[common, p2p, trie/db], stew/byteutils,
+  std/[os, parseopt, strformat, json],
+  eth/[common, trie/db], stew/byteutils,
   ../../../nimbus/db/db_chain,
   ../../../nimbus/[genesis, config, conf_utils],
   ../sim_utils
@@ -42,7 +42,13 @@ proc main() =
                    else:
                      paramStr(1)
 
+  if not caseFolder.dirExists:
+    # Handy early error message and stop directive
+    let progname = getAppFilename().extractFilename
+    quit(&"*** {progname}: Not a case folder: {caseFolder}")
+
   runTest("Consensus", caseFolder):
+    # Variable `fileName` is injected by `runTest()`
     let node = parseFile(fileName)
     processNode(fileName, node["chainfile"].getStr,
       node["lastblockhash"].getStr, testStatusIMPL)

nimbus/conf_utils.nim

@@ -19,7 +19,7 @@ type
   EthHeader = object
     header: BlockHeader
 
-proc importRlpBlock*(importFile: string, chainDB: BasechainDB): bool =
+proc importRlpBlock*(importFile: string; chainDB: BasechainDB): bool =
   let res = io2.readAllBytes(importFile)
   if res.isErr:
     error "failed to import", fileName = importFile

nimbus/p2p/chain.nim

@@ -1,7 +1,17 @@
-import ../db/db_chain, eth/common, chronicles, ../vm_state,
-  stint, nimcrypto,
-  ../utils, eth/trie/db, ./executor, ../chain_config, ../genesis, ../utils,
-  stew/endians2, ./validate, ./validate/epoch_hash_cache
+import
+  ../chain_config,
+  ../db/db_chain,
+  ../genesis,
+  ../utils,
+  ../vm_state,
+  ./executor,
+  ./validate,
+  ./validate/epoch_hash_cache,
+  chronicles,
+  eth/[common, trie/db],
+  nimcrypto,
+  stew/endians2,
+  stint
 
 when not defined(release):
   import ../tracer
@@ -130,7 +140,8 @@ method getAncestorHeader*(c: Chain, h: BlockHeader, output: var BlockHeader, ski
 method getBlockBody*(c: Chain, blockHash: KeccakHash): BlockBodyRef =
   result = nil
 
-method persistBlocks*(c: Chain, headers: openarray[BlockHeader], bodies: openarray[BlockBody]): ValidationResult {.gcsafe.} =
+method persistBlocks*(c: Chain; headers: openarray[BlockHeader];
+                  bodies: openarray[BlockBody]): ValidationResult {.gcsafe.} =
   # Run the VM here
   if headers.len != bodies.len:
     debug "Number of headers not matching number of bodies"
@@ -140,11 +151,15 @@ method persistBlocks*(c: Chain, headers: openarray[BlockHeader], bodies: openarr
   let transaction = c.db.db.beginTransaction()
   defer: transaction.dispose()
 
-  trace "Persisting blocks", fromBlock = headers[0].blockNumber, toBlock = headers[^1].blockNumber
+  trace "Persisting blocks",
+    fromBlock = headers[0].blockNumber,
+    toBlock = headers[^1].blockNumber
+
   for i in 0 ..< headers.len:
-    let head = c.db.getCanonicalHead()
-    let vmState = newBaseVMState(head.stateRoot, headers[i], c.db)
-    let validationResult = processBlock(c.db, headers[i], bodies[i], vmState)
+    let
+      head = c.db.getBlockHeader(headers[i].parentHash)
+      vmState = newBaseVMState(head.stateRoot, headers[i], c.db)
+      validationResult = processBlock(c.db, headers[i], bodies[i], vmState)
 
     when not defined(release):
       if validationResult == ValidationResult.Error and
@@ -167,10 +182,6 @@ method persistBlocks*(c: Chain, headers: openarray[BlockHeader], bodies: openarr
         return ValidationResult.Error
 
     discard c.db.persistHeaderToDb(headers[i])
-    if c.db.getCanonicalHead().blockHash != headers[i].blockHash:
-      debug "Stored block header hash doesn't match declared hash"
-      return ValidationResult.Error
-
     discard c.db.persistTransactions(headers[i].blockNumber, bodies[i].transactions)
     discard c.db.persistReceipts(vmState.receipts)