Merge #10275: [rpc] Allow fetching tx directly from specified block in getrawtransaction

434526a [test] Add tests for getrawtransaction with block hash. (Karl-Johan Alm)
b167951 [rpc] Allow getrawtransaction to take optional blockhash to fetch transaction from a block directly. (Karl-Johan Alm)
a5f5a2c [rpc] Fix fVerbose parsing (remove excess if cases). (Karl-Johan Alm)

Pull request description:

  [Reviewer hint: use [?w=1](https://github.com/bitcoin/bitcoin/pull/10275/files?w=1) to avoid seeing a bunch of indentation changes.]

  Presuming a user knows the block hash of the block containing a given transaction, this PR allows them to fetch the raw transaction, even without `-txindex`. It also enables support for getting transactions that are in orphaned blocks.

  Note that supplying a block hash will override mempool and txindex support in `GetTransaction`. The rationale behind this is that a transaction may be in multiple places (orphaned blocks) and if the user supplies an explicit block hash it should be adhered to.

  ```Bash
  $ # a41.. is a tx inside an orphan block ..3c6f.. -- first try getting it normally
  $ ./bitcoin-cli getrawtransaction a41e66ee1341aa9fb9475b98cfdc1fe1261faa56c0a49254f33065ec90f7cd79 1
  error code: -5
  error message:
  No such mempool transaction. Use -txindex to enable blockchain transaction queries. Use gettransaction for wallet transactions.
  $ # now try with block hash
  $ ./bitcoin-cli getrawtransaction a41e66ee1341aa9fb9475b98cfdc1fe1261faa56c0a49254f33065ec90f7cd79 1 0000000000000000003c6fe479122bfa4a9187493937af1734e1e5cd9f198ec7
  {
    "hex": "01000000014e7e81144e42f6d65550e59b715d470c9301fd7ac189[...]90488ac00000000",
    "inMainChain": false,
    "txid": "a41e66ee1341aa9fb9475b98cfdc1fe1261faa56c0a49254f33065ec90f7cd79",
    "hash": "a41e66ee1341aa9fb9475b98cfdc1fe1261faa56c0a49254f33065ec90f7cd79",
    "size": 225,
  [...]
  }
  $ # another tx 6c66... in block 462000
  $ ./bitcoin-cli getrawtransaction 6c66b98191e9d6cc671f6817142152ebf6c5cab2ef008397b5a71ac13255a735 1 00000000000000000217f2c12922e321f6d4aa933ce88005a9a493c503054a40
  {
    "hex": "0200000004d157[...]88acaf0c0700",
    "inMainChain": true,
    "txid": "6c66b98191e9d6cc671f6817142152ebf6c5cab2ef008397b5a71ac13255a735",
    "hash": "6c66b98191e9d6cc671f6817142152ebf6c5cab2ef008397b5a71ac13255a735",
    "size": 666,
  [...]
  }
  $
  ```

Tree-SHA512: 279be3818141edd3cc194a9ee65929331920afb30297ab2d6da07293a2d7311afee5c8b00c6457477d9f1f86e86786a9b56878ea3ee19fa2629b829d042d0cda

3 files changed, 82 insertions, 57 deletions

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 3aff1e9fbf..b26f10e476 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -64,12 +64,15 @@ void TxToJSON(const CTransaction& tx, const uint256 hashBlock, UniValue& entry)
 
 UniValue getrawtransaction(const JSONRPCRequest& request)
 {
-    if (request.fHelp || request.params.size() < 1 || request.params.size() > 2)
+    if (request.fHelp || request.params.size() < 1 || request.params.size() > 3)
         throw std::runtime_error(
-            "getrawtransaction \"txid\" ( verbose )\n"
+            "getrawtransaction \"txid\" ( verbose \"blockhash\" )\n"
 
             "\nNOTE: By default this function only works for mempool transactions. If the -txindex option is\n"
-            "enabled, it also works for blockchain transactions.\n"
+            "enabled, it also works for blockchain transactions. If the block which contains the transaction\n"
+            "is known, its hash can be provided even for nodes without -txindex. Note that if a blockhash is\n"
+            "provided, only that block will be searched and if the transaction is in the mempool or other\n"
+            "blocks, or if this node does not have the given block available, the transaction will not be found.\n"
             "DEPRECATED: for now, it also works for transactions with unspent outputs.\n"
 
             "\nReturn the raw transaction data.\n"
@@ -78,13 +81,15 @@ UniValue getrawtransaction(const JSONRPCRequest& request)
 
             "\nArguments:\n"
             "1. \"txid\"      (string, required) The transaction id\n"
-            "2. verbose       (bool, optional, default=false) If false, return a string, otherwise return a json object\n"
+            "2. verbose     (bool, optional, default=false) If false, return a string, otherwise return a json object\n"
+            "3. \"blockhash\" (string, optional) The block in which to look for the transaction\n"
 
             "\nResult (if verbose is not set or set to false):\n"
             "\"data\"      (string) The serialized, hex-encoded data for 'txid'\n"
 
             "\nResult (if verbose is set to true):\n"
             "{\n"
+            "  \"in_active_chain\": b, (bool) Whether specified block is in the active chain or not (only present with explicit \"blockhash\" argument)\n"
             "  \"hex\" : \"data\",       (string) The serialized, hex-encoded data for 'txid'\n"
             "  \"txid\" : \"id\",        (string) The transaction id (same as provided)\n"
             "  \"hash\" : \"id\",        (string) The transaction hash (differs from txid for witness transactions)\n"
@@ -132,42 +137,58 @@ UniValue getrawtransaction(const JSONRPCRequest& request)
             + HelpExampleCli("getrawtransaction", "\"mytxid\"")
             + HelpExampleCli("getrawtransaction", "\"mytxid\" true")
             + HelpExampleRpc("getrawtransaction", "\"mytxid\", true")
+            + HelpExampleCli("getrawtransaction", "\"mytxid\" false \"myblockhash\"")
+            + HelpExampleCli("getrawtransaction", "\"mytxid\" true \"myblockhash\"")
         );
 
     LOCK(cs_main);
 
+    bool in_active_chain = true;
     uint256 hash = ParseHashV(request.params[0], "parameter 1");
+    CBlockIndex* blockindex = nullptr;
 
     // Accept either a bool (true) or a num (>=1) to indicate verbose output.
     bool fVerbose = false;
     if (!request.params[1].isNull()) {
-        if (request.params[1].isNum()) {
-            if (request.params[1].get_int() != 0) {
-                fVerbose = true;
-            }
-        }
-        else if(request.params[1].isBool()) {
-            if(request.params[1].isTrue()) {
-                fVerbose = true;
+        fVerbose = request.params[1].isNum() ? (request.params[1].get_int() != 0) : request.params[1].get_bool();
+    }
+
+    if (!request.params[2].isNull()) {
+        uint256 blockhash = ParseHashV(request.params[2], "parameter 3");
+        if (!blockhash.IsNull()) {
+            BlockMap::iterator it = mapBlockIndex.find(blockhash);
+            if (it == mapBlockIndex.end()) {
+                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block hash not found");
             }
-        }
-        else {
-            throw JSONRPCError(RPC_TYPE_ERROR, "Invalid type provided. Verbose parameter must be a boolean.");
+            blockindex = it->second;
+            in_active_chain = chainActive.Contains(blockindex);
         }
     }
 
     CTransactionRef tx;
-    uint256 hashBlock;
-    if (!GetTransaction(hash, tx, Params().GetConsensus(), hashBlock, true))
-        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, std::string(fTxIndex ? "No such mempool or blockchain transaction"
-            : "No such mempool transaction. Use -txindex to enable blockchain transaction queries") +
-            ". Use gettransaction for wallet transactions.");
+    uint256 hash_block;
+    if (!GetTransaction(hash, tx, Params().GetConsensus(), hash_block, true, blockindex)) {
+        std::string errmsg;
+        if (blockindex) {
+            if (!(blockindex->nStatus & BLOCK_HAVE_DATA)) {
+                throw JSONRPCError(RPC_MISC_ERROR, "Block not available");
+            }
+            errmsg = "No such transaction found in the provided block";
+        } else {
+            errmsg = fTxIndex
+              ? "No such mempool or blockchain transaction"
+              : "No such mempool transaction. Use -txindex to enable blockchain transaction queries";
+        }
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, errmsg + ". Use gettransaction for wallet transactions.");
+    }
 
-    if (!fVerbose)
+    if (!fVerbose) {
         return EncodeHexTx(*tx, RPCSerializationFlags());
+    }
 
     UniValue result(UniValue::VOBJ);
-    TxToJSON(*tx, hashBlock, result);
+    if (blockindex) result.push_back(Pair("in_active_chain", in_active_chain));
+    TxToJSON(*tx, hash_block, result);
     return result;
 }
 
@@ -995,7 +1016,7 @@ UniValue sendrawtransaction(const JSONRPCRequest& request)
 static const CRPCCommand commands[] =
 { //  category              name                      actor (function)         argNames
   //  --------------------- ------------------------  -----------------------  ----------
-    { "rawtransactions",    "getrawtransaction",      &getrawtransaction,      {"txid","verbose"} },
+    { "rawtransactions",    "getrawtransaction",      &getrawtransaction,      {"txid","verbose","blockhash"} },
     { "rawtransactions",    "createrawtransaction",   &createrawtransaction,   {"inputs","outputs","locktime","replaceable"} },
     { "rawtransactions",    "decoderawtransaction",   &decoderawtransaction,   {"hexstring"} },
     { "rawtransactions",    "decodescript",           &decodescript,           {"hexstring"} },
diff --git a/src/validation.cpp b/src/validation.cpp
index 98db699566..986052771c 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -926,47 +926,51 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
     return AcceptToMemoryPoolWithTime(chainparams, pool, state, tx, pfMissingInputs, GetTime(), plTxnReplaced, bypass_limits, nAbsurdFee);
 }
 
-/** Return transaction in txOut, and if it was found inside a block, its hash is placed in hashBlock */
-bool GetTransaction(const uint256 &hash, CTransactionRef &txOut, const Consensus::Params& consensusParams, uint256 &hashBlock, bool fAllowSlow)
+/**
+ * Return transaction in txOut, and if it was found inside a block, its hash is placed in hashBlock.
+ * If blockIndex is provided, the transaction is fetched from the corresponding block.
+ */
+bool GetTransaction(const uint256& hash, CTransactionRef& txOut, const Consensus::Params& consensusParams, uint256& hashBlock, bool fAllowSlow, CBlockIndex* blockIndex)
 {
-    CBlockIndex *pindexSlow = nullptr;
+    CBlockIndex* pindexSlow = blockIndex;
 
     LOCK(cs_main);
 
-    CTransactionRef ptx = mempool.get(hash);
-    if (ptx)
-    {
-        txOut = ptx;
-        return true;
-    }
-
-    if (fTxIndex) {
-        CDiskTxPos postx;
-        if (pblocktree->ReadTxIndex(hash, postx)) {
-            CAutoFile file(OpenBlockFile(postx, true), SER_DISK, CLIENT_VERSION);
-            if (file.IsNull())
-                return error("%s: OpenBlockFile failed", __func__);
-            CBlockHeader header;
-            try {
-                file >> header;
-                fseek(file.Get(), postx.nTxOffset, SEEK_CUR);
-                file >> txOut;
-            } catch (const std::exception& e) {
-                return error("%s: Deserialize or I/O error - %s", __func__, e.what());
-            }
-            hashBlock = header.GetHash();
-            if (txOut->GetHash() != hash)
-                return error("%s: txid mismatch", __func__);
+    if (!blockIndex) {
+        CTransactionRef ptx = mempool.get(hash);
+        if (ptx) {
+            txOut = ptx;
             return true;
         }
 
-        // transaction not found in index, nothing more can be done
-        return false;
-    }
+        if (fTxIndex) {
+            CDiskTxPos postx;
+            if (pblocktree->ReadTxIndex(hash, postx)) {
+                CAutoFile file(OpenBlockFile(postx, true), SER_DISK, CLIENT_VERSION);
+                if (file.IsNull())
+                    return error("%s: OpenBlockFile failed", __func__);
+                CBlockHeader header;
+                try {
+                    file >> header;
+                    fseek(file.Get(), postx.nTxOffset, SEEK_CUR);
+                    file >> txOut;
+                } catch (const std::exception& e) {
+                    return error("%s: Deserialize or I/O error - %s", __func__, e.what());
+                }
+                hashBlock = header.GetHash();
+                if (txOut->GetHash() != hash)
+                    return error("%s: txid mismatch", __func__);
+                return true;
+            }
 
-    if (fAllowSlow) { // use coin database to locate block that contains transaction, and scan it
-        const Coin& coin = AccessByTxid(*pcoinsTip, hash);
-        if (!coin.IsSpent()) pindexSlow = chainActive[coin.nHeight];
+            // transaction not found in index, nothing more can be done
+            return false;
+        }
+
+        if (fAllowSlow) { // use coin database to locate block that contains transaction, and scan it
+            const Coin& coin = AccessByTxid(*pcoinsTip, hash);
+            if (!coin.IsSpent()) pindexSlow = chainActive[coin.nHeight];
+        }
     }
 
     if (pindexSlow) {
diff --git a/src/validation.h b/src/validation.h
index 254f3e0754..ec17d0d92d 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -273,7 +273,7 @@ void ThreadScriptCheck();
 /** Check whether we are doing an initial block download (synchronizing from disk or network) */
 bool IsInitialBlockDownload();
 /** Retrieve a transaction (from memory pool, or from disk, if possible) */
-bool GetTransaction(const uint256 &hash, CTransactionRef &tx, const Consensus::Params& params, uint256 &hashBlock, bool fAllowSlow = false);
+bool GetTransaction(const uint256& hash, CTransactionRef& tx, const Consensus::Params& params, uint256& hashBlock, bool fAllowSlow = false, CBlockIndex* blockIndex = nullptr);
 /** Find the best known block, and make it the tip of the block chain */
 bool ActivateBestChain(CValidationState& state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>());
 CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams);