Lua on each mapgen thread (#13092)

games/devtest/mods/unittests/inside_mapgen_env.lua

@@ -0,0 +1,32 @@
+core.log("info", "Hello World")
+
+local function do_tests()
+	assert(core == minetest)
+	-- stuff that should not be here
+	assert(not core.get_player_by_name)
+	assert(not core.object_refs)
+	-- stuff that should be here
+	assert(core.register_on_generated)
+	assert(core.get_node)
+	assert(core.spawn_tree)
+	assert(ItemStack)
+	local meta = ItemStack():get_meta()
+	assert(type(meta) == "userdata")
+	assert(type(meta.set_tool_capabilities) == "function")
+	assert(core.registered_items[""])
+	assert(core.save_gen_notify)
+	-- alias handling
+	assert(core.registered_items["unittests:steel_ingot_alias"].name ==
+		"unittests:steel_ingot")
+	-- fallback to item defaults
+	assert(core.registered_items["unittests:description_test"].on_place == true)
+end
+
+-- there's no (usable) communcation path between mapgen and the regular env
+-- so we just run the test unconditionally
+do_tests()
+
+core.register_on_generated(function(vm, pos1, pos2, blockseed)
+	local n = tonumber(core.get_mapgen_setting("chunksize")) * 16 - 1
+	assert(pos2:subtract(pos1) == vector.new(n, n, n))
+end)