Merge pull request 'MISC/mcl_selftests: Do not crash if minetest.find_nodes_in_area() lies' (#214) from fix-selftest-crash into master

Reviewed-on: https://git.minetest.land/Mineclonia/Mineclonia/pulls/214
Reviewed-by: cora <cora@noreply.git.minetest.land>

mods/MISC/mcl_selftests/init.lua

@@ -75,14 +75,22 @@ local test_minetest_find_nodes_in_area_can_count = function(dtime)
 	local nodes_expected = math.pow( 1 + (2 * radius), 3 )
 	local nodes_counted = nnum[nodename]
 	local nodes_difference = nodes_expected - nodes_counted
-	-- Yes, the following line is supposed to crash the game in
-	-- the case that Minetest forgot how to count the number of
-	-- nodes in a three dimensional volume it just filled. This
-	-- function contains an excellent explanation on what not to
-	-- do further up. I strongly suggest to pester Minetest core
-	-- devs about this issue and not the author of the function,
-	-- should this test ever fail.
-	assert ( 0 == nodes_difference )
+	-- Originally, there was an assertion here that made the game
+	-- crash at startup if Minetest forgot how to count. This was
+	-- originally intended to avoid buggy engine releases, but it
+	-- mostly made people upset and hindered debugging. Also, the
+	-- assertion contained no error message hinting at the reason
+	-- for the crash, making it exceptionally user-unfriendly. It
+	-- follows that a game or mod should only assert on behaviour
+	-- of the Lua code, not the underlying implementation, unless
+	-- engine bugs are bad enough to permanently corrupt a world.
+	if ( 0 ~= nodes_difference ) then
+		minetest.debug(
+			"minetest.find_nodes_in_area() failed to find " ..
+			nodes_difference .. " nodes that were placed. " ..
+			"Downgrading to Minetest 5.4.1 might fix this."
+		)
+	end
 end
 
 minetest.after( 0, test_minetest_find_nodes_in_area_can_count )