Fix lua lint warnings reported by emmylua

The largest source was compat.lua returning the setmetatable call
directly, which made emmylua infer the module type from the metatable
rather than the LibCompat class, hiding every field from consumers.

The remaining fixes are nil guards on gui element and character
accesses, type annotations for research_sync's script data and
player_auth's rcon arguments, casts where the api's read/write union
types are wider than the values at runtime, and scoped diagnostic
disables for the vendored json.lua and the version fallback code that
touches apis removed from the current typedefs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/host/lua/export/control.lua

@@ -1,3 +1,6 @@
+--- Undefined fields are expected, the typedefs only cover the latest version
+--- @diagnostic disable: undefined-field
+
 local function send_json(channel, data)
 	data = helpers and helpers.table_to_json(data) or game.table_to_json(data)
 	print("\f$ipc:" .. channel .. "?j" .. data)

packages/host/modules/clusterio/compat.lua

@@ -10,7 +10,8 @@ Implementation Guidelines
 
 local lib_json = require("json")
 
---- @diagnostic disable: deprecated
+--- Undefined fields are expected, the typedefs only cover the latest version
+--- @diagnostic disable: deprecated, undefined-field
 
 --- @class LibCompat
 --- @field script_data table
@@ -238,4 +239,6 @@ set_script_data()
 compat.on_init = set_script_data --- @package
 compat.on_load = set_script_data --- @package
 
-return setmetatable(compat, compat_mt)
+-- Not returned directly because that would infer the metatable type rather than LibCompat
+setmetatable(compat, compat_mt)
+return compat

packages/host/modules/clusterio/json.lua

@@ -22,6 +22,9 @@
 -- SOFTWARE.
 --
 
+--- Vendored file, the forward declared recursion is not worth annotating
+--- @diagnostic disable: need-check-nil
+
 local json = { _version = "0.1.2" }
 
 -------------------------------------------------------------------------------

plugins/inventory_sync/module/restore_position.lua

@@ -21,9 +21,10 @@ return function(player, record)
 		player.driving = true
 
 		-- Teleport to safe location if unable to enter vehicle
-		if not player.driving and player.controller_type == defines.controllers.character then
+		local character = player.character
+		if not player.driving and character and player.controller_type == defines.controllers.character then
 			local safe_position = record.vehicle.surface.find_non_colliding_position(
-				player.character.name, player.position, 32, 1/8
+				character.name, player.position, 32, 1/8
 			)
 			if safe_position then
 				player.teleport(safe_position, player.surface)

plugins/inventory_sync/module/serialize.lua

@@ -207,14 +207,14 @@ end
 --- @return QuickBarSlotEncoded
 local function serialize_filter(filter)
 	if filter.quality == "normal" and filter.comparator == "=" then
-		return filter.name
+		return filter.name --[[@as string]]
 	end
 
 	return {
 		t = "f",
-		n = filter.name,
-		q = filter.quality,
-		c = filter.comparator,
+		n = filter.name --[[@as string]],
+		q = filter.quality --[[@as string]],
+		c = filter.comparator --[[@as string]],
 	}
 end
 
@@ -234,7 +234,7 @@ function serialize.serialize_quick_bar_slot(slot)
 
 	if v2_0_quick_bar_api then
 		-- 2.0 gives us an item filter which supports quality
-		--- @cast slot ItemFilter
+		--- @cast slot -QuickBarSlot, -LuaItemPrototype
 		return serialize_filter(slot)
 	end
 
@@ -267,7 +267,7 @@ function serialize.deserialize_quick_bar_slot(entry)
 					quality = entry.q,
 					comparator = entry.c,
 				},
-			}
+			} --[[@as QuickBarSlot]]
 		end
 
 		print("Warning: Unsupported serialized quick bar slot type '" .. tostring(entry.t) .. "'")
@@ -292,7 +292,7 @@ function serialize.deserialize_quick_bar_slot(entry)
 
 	-- Return a string (member of ItemPrototypeIdentification)
 	-- Pre 2.0 this was the only method of encoding used
-	return entry
+	return entry --[[@as string]]
 end
 
 --- @param player LuaPlayer
@@ -709,7 +709,8 @@ local function ensure_character(player)
 	local surface = player.surface
 	if v2_space_platform and surface.platform then
 		local planet_surface = find_planet_surface(surface.platform)
-		player.teleport(player.force.get_spawn_position(planet_surface), planet_surface)
+		local force = player.force --[[@as LuaForce]]
+		player.teleport(force.get_spawn_position(planet_surface), planet_surface)
 	end
 
 	-- Create and return the character
@@ -721,7 +722,7 @@ local function ensure_character(player)
 			player.surface.name, tostring(player.connected), tostring(player.driving)
 		))
 	end
-	return player.character
+	return assert(player.character)
 end
 
 --- @class FailedDeserializationPlayerData

plugins/player_auth/module/auth.lua

@@ -132,6 +132,7 @@ function auth.add_commands()
 		end
 
 		if event.parameter then
+			--- @type string[]
 			local args = {}
 			for w in string.gmatch(event.parameter, "[^ ]+") do
 				args[#args + 1] = w
@@ -149,7 +150,7 @@ function auth.add_commands()
 				end
 
 				local player_name, url, code = table.unpack(args)
-				local player = game.players[player_name]
+				local player = game.get_player(player_name)
 				if not player then
 					rcon.print("Player " .. player_name .. " does not exist")
 					return
@@ -159,7 +160,7 @@ function auth.add_commands()
 
 			elseif command == "code_set" then
 				local player_name = args[1]
-				local player = game.players[player_name]
+				local player = game.get_player(player_name)
 				if not player then
 					rcon.print("Player " .. player_name .. " does not exist")
 					return
@@ -171,7 +172,7 @@ function auth.add_commands()
 
 			elseif command == "error" then
 				local player_name = table.remove(args, 1)
-				local player = game.players[player_name]
+				local player = game.get_player(player_name)
 				if not player then
 					rcon.print("Player " .. player_name .. " does not exist")
 					return
@@ -192,10 +193,12 @@ auth.events[defines.events.on_gui_click] = function(event)
 	end
 
 	if event.element.name == "player_auth_dialog_close_button" then
-		event.element.parent.parent.destroy()
+		local parent = assert(event.element.parent)
+		assert(parent.parent).destroy()
 
 	elseif event.element.name == "player_auth_verify_code_button" then
-		local verify_code = event.element.parent.player_auth_verify_code_input.text
+		local parent = assert(event.element.parent)
+		local verify_code = assert(parent.player_auth_verify_code_input).text
 		local player_name = game.players[event.player_index].name
 		clusterio_api.send_json("player_auth", {
 			type = "set_verify_code",

plugins/research_sync/module/sync.lua

@@ -30,8 +30,17 @@ local function set_technology_progress(tech, progress)
 	end
 end
 
+--- @class ResearchSyncTechnology
+--- @field level uint
+--- @field researched boolean?
+--- @field progress double?
+
+--- @class ResearchSyncData
+--- @field technologies table<string, ResearchSyncTechnology>
+--- @field ignore_research_finished boolean
+
 --- @param no_early_return boolean?
---- @return table
+--- @return ResearchSyncData
 local function get_script_data(no_early_return)
 	local research_sync = compat.script_data.research_sync
 	if research_sync and not no_early_return then

plugins/statistics_exporter/module/export.lua

@@ -32,6 +32,7 @@ function statistics_exporter.export()
 		for _, force in pairs(game.forces) do
 			local flow_statistics = {}
 			for _, statName in pairs(statistics) do
+				--- @type LuaFlowStatistics
 				local stat = v2_stats and force["get_" .. statName](surface.index) or force[statName]
 				flow_statistics[statName] = {
 					input = stat.input_counts,