From 9f7501d20a0eda96bbf348a5e4470bc464baccba Mon Sep 17 00:00:00 2001
From: sfan5 <sfan5@live.de>
Date: Sun, 25 May 2025 19:16:58 +0200
Subject: [PATCH] Handle writing to unloaded blocks in MMVManip::blitBackAll()

This could happen before and would just silently discard the data,
but now that Lua can create VManips without loading from map beforehand
we definitely need to handle this case.
---
 src/map.cpp   | 37 ++++++++++++++++++++++---------------
 src/voxel.cpp |  1 -
 src/voxel.h   |  1 -
 3 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/src/map.cpp b/src/map.cpp
index 1c1dfd51c..964d8b5af 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -789,20 +789,10 @@ void MMVManip::initialEmerge(v3s16 p_min, v3s16 p_max, bool load_if_inexistent)
 		if (auto it = had_blocks.find(p); it != had_blocks.end() && it->second)
 			continue;
 
-		MapBlock *block;
-		bool block_data_inexistent = false;
-		{
-			TimeTaker timer2("emerge load", &emerge_load_time);
-
-			block = m_map->getBlockNoCreateNoEx(p);
-			if (!block)
-				block_data_inexistent = true;
-			else
-				block->copyTo(*this);
-		}
-
-		if(block_data_inexistent)
-		{
+		MapBlock *block = m_map->getBlockNoCreateNoEx(p);
+		if (block) {
+			block->copyTo(*this);
+		} else {
 			if (load_if_inexistent && !blockpos_over_max_limit(p)) {
 				block = m_map->emergeBlock(p, true);
 				assert(block);
@@ -862,6 +852,8 @@ void MMVManip::blitBackAll(std::map<v3s16, MapBlock*> *modified_blocks,
 		return;
 	assert(m_map);
 
+	size_t nload = 0;
+
 	// Copy all the blocks with data back to the map
 	const auto loaded_blocks = getCoveredBlocks();
 	for (auto &it : loaded_blocks) {
@@ -869,7 +861,18 @@ void MMVManip::blitBackAll(std::map<v3s16, MapBlock*> *modified_blocks,
 			continue;
 		v3s16 p = it.first;
 		MapBlock *block = m_map->getBlockNoCreateNoEx(p);
-		if (!block || (!overwrite_generated && block->isGenerated()))
+		if (!block) {
+			if (!blockpos_over_max_limit(p)) {
+				block = m_map->emergeBlock(p, true);
+				nload++;
+			}
+		}
+		if (!block) {
+			warningstream << "blitBackAll: Couldn't load block " << p
+				<< " to write data to map" << std::endl;
+			continue;
+		}
+		if (!overwrite_generated && block->isGenerated())
 			continue;
 
 		block->copyFrom(*this);
@@ -879,6 +882,10 @@ void MMVManip::blitBackAll(std::map<v3s16, MapBlock*> *modified_blocks,
 		if(modified_blocks)
 			(*modified_blocks)[p] = block;
 	}
+
+	if (nload > 0) {
+		verbosestream << "blitBackAll: " << nload << " blocks had to be loaded for writing" << std::endl;
+	}
 }
 
 MMVManip *MMVManip::clone() const
diff --git a/src/voxel.cpp b/src/voxel.cpp
index 4d0ce84b7..5a69b0725 100644
--- a/src/voxel.cpp
+++ b/src/voxel.cpp
@@ -15,7 +15,6 @@
 	Debug stuff
 */
 u64 emerge_time = 0;
-u64 emerge_load_time = 0;
 
 VoxelManipulator::~VoxelManipulator()
 {
diff --git a/src/voxel.h b/src/voxel.h
index a1a3784e5..7fbaadc28 100644
--- a/src/voxel.h
+++ b/src/voxel.h
@@ -34,7 +34,6 @@ class NodeDefManager;
 	Debug stuff
 */
 extern u64 emerge_time;
-extern u64 emerge_load_time;
 
 /*
 	This class resembles aabbox3d<s16> a lot, but has inclusive