From 3f00c1d1cb3823f405558b2bd23465813580d5e3 Mon Sep 17 00:00:00 2001
From: HybridDog <ovvv@web.de>
Date: Tue, 9 Feb 2016 11:32:09 +0100
Subject: [PATCH 1/2] fix pistons not working in every buildable_to node

---
 mesecons_mvps/init.lua | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/mesecons_mvps/init.lua b/mesecons_mvps/init.lua
index beec94b..6f455f7 100644
--- a/mesecons_mvps/init.lua
+++ b/mesecons_mvps/init.lua
@@ -47,6 +47,17 @@ function mesecon.mvps_process_stack(stack)
 	end
 end
 
+-- tests if the node can't be pushed
+local replaceable_cache = {air = true, ignore = false}
+local function node_replaceable(name)
+	if replaceable_cache[name] ~= nil then
+		return replaceable_cache[name]
+	end
+	local replaceable = not minetest.registered_nodes[name] or minetest.registered_nodes[name].buildable_to or false
+	replaceable_cache[name] = replaceable
+	return replaceable
+end
+
 function mesecon.mvps_get_stack(pos, dir, maximum, all_pull_sticky)
 	-- determine the number of nodes to be pushed
 	local nodes = {}
@@ -56,9 +67,7 @@ function mesecon.mvps_get_stack(pos, dir, maximum, all_pull_sticky)
 		local np = frontiers[1]
 		local nn = minetest.get_node(np)
 
-		if nn.name ~= "air"
-		and minetest.registered_nodes[nn.name]
-		and minetest.registered_nodes[nn.name].liquidtype == "none" then
+		if not node_replaceable(nn.name) then
 			table.insert(nodes, {node = nn, pos = np})
 			if #nodes > maximum then return nil end
 

From cf45e24c57306450215b27d9bcbca43084d57d32 Mon Sep 17 00:00:00 2001
From: HybridDog <ovvv@web.de>
Date: Tue, 9 Feb 2016 16:58:49 +0100
Subject: [PATCH 2/2] this way it works better because unknown nodes may not
 stay unknown

---
 mesecons_mvps/init.lua | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mesecons_mvps/init.lua b/mesecons_mvps/init.lua
index 6f455f7..bfbd774 100644
--- a/mesecons_mvps/init.lua
+++ b/mesecons_mvps/init.lua
@@ -19,6 +19,12 @@ function mesecon.is_mvps_stopper(node, pushdir, stack, stackid)
 	if type (get_stopper) == "function" then
 		get_stopper = get_stopper(node, pushdir, stack, stackid)
 	end
+	if get_stopper == nil
+	and not minetest.registered_nodes[node.name] then
+		-- unknown nodes must be stoppers
+		mesecon.mvps_stoppers[node.name] = true
+		get_stopper = true
+	end
 	return get_stopper
 end
 
@@ -53,7 +59,8 @@ local function node_replaceable(name)
 	if replaceable_cache[name] ~= nil then
 		return replaceable_cache[name]
 	end
-	local replaceable = not minetest.registered_nodes[name] or minetest.registered_nodes[name].buildable_to or false
+	--local replaceable = not minetest.registered_nodes[name] or minetest.registered_nodes[name].buildable_to or false
+	local replaceable = (minetest.registered_nodes[name] and minetest.registered_nodes[name].buildable_to) or false
 	replaceable_cache[name] = replaceable
 	return replaceable
 end