From 45c0b2b82b648d9e7a0d42eceb09df6cf7ba2e6e Mon Sep 17 00:00:00 2001
From: William Berman <wlbberman@gmail.com>
Date: Mon, 11 Jan 2021 13:00:44 -0800
Subject: [PATCH] Transactions in unsynced blocks no-longer assumed pruned

---
 storage/modules/block_storage.go      | 16 +++++++++++++---
 storage/modules/block_storage_test.go | 17 +++++++++++++++--
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/storage/modules/block_storage.go b/storage/modules/block_storage.go
index 8875921a..5b18ba0b 100644
--- a/storage/modules/block_storage.go
+++ b/storage/modules/block_storage.go
@@ -1063,25 +1063,35 @@ func (b *BlockStorage) FindTransaction(
 
 	var newestBlock *types.BlockIdentifier
 	var newestTransaction *types.Transaction
+	var transactionUnsequenced bool
 	for _, blockTransaction := range blockTransactions {
 		if newestBlock == nil || blockTransaction.BlockIdentifier.Index > newestBlock.Index {
 			// Now that we are optimistically storing data, there is a chance
 			// we may fetch a transaction from a seen but unsequenced block.
 			if head != nil && blockTransaction.BlockIdentifier.Index > head.Index {
+				// We have seen a transaction, but it's in a block that is not yet
+				// sequenced.
+				transactionUnsequenced = true
 				continue
 			}
 
 			newestBlock = blockTransaction.BlockIdentifier
+			// When `blockTransaction` is pruned, `blockTransaction.Transaction` is set to nil
 			newestTransaction = blockTransaction.Transaction
 		}
 	}
 
-	// If the transaction has been pruned, it will be nil.
-	if newestTransaction == nil {
+	if newestTransaction != nil {
+		return newestBlock, newestTransaction, nil
+	}
+
+	if !transactionUnsequenced {
+		// All matching transaction have been pruned
 		return nil, nil, storageErrs.ErrCannotAccessPrunedData
 	}
 
-	return newestBlock, newestTransaction, nil
+	// A transaction exists but we have not yet sequenced the block it is in
+	return nil, nil, nil
 }
 
 func (b *BlockStorage) findBlockTransaction(
diff --git a/storage/modules/block_storage_test.go b/storage/modules/block_storage_test.go
index 08c92ce6..2c0cafed 100644
--- a/storage/modules/block_storage_test.go
+++ b/storage/modules/block_storage_test.go
@@ -356,12 +356,25 @@ func TestBlock(t *testing.T) {
 		err = storage.SeeBlock(ctx, newBlock)
 		assert.NoError(t, err)
 
+		// Attempt to find transaction before it's synced
+		transaction := storage.db.ReadTransaction(ctx)
+		newestBlock, newestTransaction, err := storage.FindTransaction(
+			ctx,
+			newBlock.Transactions[0].TransactionIdentifier,
+			transaction,
+		)
+		assert.NoError(t, err)
+		assert.Nil(t, newestBlock)
+		assert.Nil(t, newestTransaction)
+		transaction.Discard(ctx)
+
 		// Ensure we can FindTransaction in add block transaction.
-		transaction := storage.db.WriteTransaction(ctx, blockSyncIdentifier, true)
+		transaction = storage.db.WriteTransaction(ctx, blockSyncIdentifier, true)
+		// Sequence the block so the transaction can be found
 		err = storage.storeBlock(ctx, transaction, newBlock.BlockIdentifier)
 		assert.NoError(t, err)
 
-		newestBlock, newestTransaction, err := storage.FindTransaction(
+		newestBlock, newestTransaction, err = storage.FindTransaction(
 			ctx,
 			newBlock.Transactions[0].TransactionIdentifier,
 			transaction,