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

1 files changed, 37 insertions, 33 deletions

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) {