Luau Type Improvements (#76)

This PR makes some improvements to the existing Luau types, including:

Improves reuse of the Action type
Fixes contravariance issue with Store type
Allows thunks to be void returning

Author: jkelaty-rbx

.gitignore

@@ -17,6 +17,10 @@ roblox.toml
 # Darklua
 **/darklua*
 
+# Analysis artifacts
+sourcemap.json
+globalTypes.d.lua
+
 # Misc OS and editor files
 .DS_Store
 .vscode

foreman.toml

@@ -1,6 +1,6 @@
 [tools]
-rojo = { source = "rojo-rbx/rojo", version = "7.2.0" }
-selene = { source = "Kampfkarren/selene", version = "0.21.1" }
-stylua = { source = "JohnnyMorganz/StyLua", version = "0.15.1" }
-luau-lsp = { source = "JohnnyMorganz/luau-lsp", version = "*" }
-wally = { source = "UpliftGames/wally", version = "0.3.1" }
+rojo = { source = "rojo-rbx/rojo", version = "=7.2.1" }
+selene = { source = "Kampfkarren/selene", version = "=0.21.1" }
+stylua = { source = "JohnnyMorganz/StyLua", version = "=0.15.1" }
+luau-lsp = { source = "JohnnyMorganz/luau-lsp", version = "=1.8.1" }
+wally = { source = "UpliftGames/wally", version = "=0.3.1" }

src/loggerMiddleware.lua

@@ -1,4 +1,3 @@
---!strict
 -- We want to be able to override outputFunction in tests, so the shape of this
 -- module is kind of unconventional.
 --

src/makeActionCreator.lua

@@ -5,17 +5,19 @@
 
 local actions = require(script.Parent.types.actions)
 
+export type Action<Type> = actions.Action<Type>
+
 export type ActionCreator<Type, Action, Args...> = actions.ActionCreator<Type, Action, Args...>
 
-local function makeActionCreator<Type, Action, Args...>(name: Type, fn: (Args...) -> Action): ActionCreator<Type, Action, Args...>
+local function makeActionCreator<Type, Payload, Args...>(name: Type, fn: (Args...) -> Payload): ActionCreator<Type, Payload, Args...>
 	assert(type(name) == "string", "Bad argument #1: Expected a string name for the action creator")
 
 	assert(type(fn) == "function", "Bad argument #2: Expected a function that creates action objects")
 
 	return setmetatable({
 		name = name,
 	}, {
-		__call = function(_self: any, ...: Args...): Action & { type: Type }
+		__call = function(_self: any, ...: Args...): Payload & Action<Type>
 			local result = fn(...)
 
 			assert(type(result) == "table", "Invalid action: An action creator must return a table")

src/makeThunkMiddleware.lua

@@ -1,4 +1,3 @@
---!strict
 --[[
 	A middleware that allows for functions to be dispatched with an extra
 	argument for convenience. Functions will receive two arguments:

src/types/actions.lua

@@ -3,13 +3,13 @@ export type Action<Type = any> = {
 	type: Type,
 }
 
-export type AnyAction = Action & {
+export type AnyAction = {
 	[string]: any,
-}
+} & Action
 
-export type ActionCreator<Type, Action, Args...> = typeof(setmetatable(
+export type ActionCreator<Type, Payload, Args...> = typeof(setmetatable(
 	{} :: { name: Type },
-	{} :: { __call: (any, Args...) -> (Action & { type: Type }) }
+	{} :: { __call: (any, Args...) -> (Payload & Action<Type>) }
 ))
 
 return nil

src/types/store.lua

@@ -13,8 +13,15 @@ export type Dispatch<State = any> = IDispatch<Store<State>>
 export type IStore<State, Dispatch> = {
 	dispatch: Dispatch,
 	getState: (self: IStore<State, Dispatch>) -> State,
-	destruct: (self: IStore<State, Dispatch>) -> (),
-	flush: (self: IStore<State, Dispatch>) -> (),
+
+	--[[
+		FIXME LUAU: Typing self as any here is a hack to skirt around
+		variance-related issues with tables. Read-write properties
+		should obviate the need for this workaround.
+	]]
+	destruct: (self: any) -> (),
+	flush: (self: any) -> (),
+
 	changed: RBXScriptSignal,
 }
 export type Store<State = any> = IStore<State, Dispatch<State>>

src/types/thunks.lua

@@ -4,7 +4,7 @@ local store = require(script.Parent.store)
 type IStore<State, Dispatch> = store.IStore<State, Dispatch>
 type IDispatch<Store> = store.IDispatch<Store>
 
-export type IThunkAction<ReturnType, Store> = (store: Store) -> ReturnType
+export type IThunkAction<ReturnType, Store> = ((store: Store) -> ReturnType) | ((store: Store) -> ())
 export type ThunkAction<ReturnType, State = any> = IThunkAction<ReturnType, ThunkfulStore<State>>
 
 export type IThunkDispatch<Store> = <ReturnType>(