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Somewhat working version of promise_tech
Now with tests in a block comment at the bottom!
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@ -20,6 +20,7 @@ Promise.new = function(fn)
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local result = {
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state = "pending",
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force_reject = false,
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fn = fn
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}
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setmetatable(result, Promise)
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@ -34,17 +35,22 @@ end
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*************************
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--]]
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--- A dummy function
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local f = function(val) end
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--- Then function for promises
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-- @param onFulfilled <function>: The function to call if the promise is fulfilled
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-- @param onRejected <function>: The function to call if the promise is rejected
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-- @return A promise object
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-- @return A promise object containing a table of results
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Promise.then_ = function(self, onFulfilled, onRejected)
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-- onFulfilled must be a function
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if type(onFulfilled) ~= "function" and onRejected ~= nil then
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-- onFulfilled must be a function or nil
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if onFulfilled == nil then onFulfilled = f
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elseif type(onFulfilled) ~= "function" then
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error("Error (Promise.then_): First argument (onFulfilled) must be a function or nil")
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end
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-- onRejected must be a function or nil
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if type(onRejected) ~= "function" and onRejected ~= nil then
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if onRejected == nil then onRejected = f
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elseif type(onRejected) ~= "function" then
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error("Error (Promise.then_): Second argument (onRejected) must be a function or nil")
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end
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-- If self.state is not "pending" then error
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@ -52,20 +58,27 @@ Promise.then_ = function(self, onFulfilled, onRejected)
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error("Error (Promise.then_): Promise is already " .. self.state)
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end
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local result = function()
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local success, value = pcall(self.fn, onFulfilled, onRejected)
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return Promise.new(function(resolve, reject)
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if success then
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resolve(value)
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self.state = "fulfilled"
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else
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reject(value)
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self.state = "rejected"
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end
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end)
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-- Make locals to collect the results of self.fn
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local result, force_reject = {nil}, self.force_reject
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-- Local resolve and reject functions
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local _resolve = function(value) result[1] = value end
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local _reject = function(value)
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result[1] = value
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force_reject = true
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end
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return result()
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-- Call self.fn
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local success, err = pcall(self.fn, _resolve, _reject)
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-- Return a new promise with the results
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if success and not force_reject then
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onFulfilled(result[1])
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return Promise.resolve(result[1])
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else
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onRejected(result[1])
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return Promise.reject(success and result[1] or err)
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end
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end
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--- Catch function for promises
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@ -107,9 +120,50 @@ end
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-- @param value <any>: The value to reject the promise with
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-- @return A promise object
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Promise.reject = function(value)
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return Promise.new(function(resolve, reject)
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local promise = Promise.new(function(resolve, reject)
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reject(value)
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end)
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promise.force_reject = true
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return promise
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end
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-- TODO: Implement static methods (all, any, race etc.)
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return Promise
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--- TESTS
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--[[
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Promise = require "promise_tech"
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tmp = Promise.resolve(5)
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tmp:then_(print, nil)
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tmp = Promise.reject(7)
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tmp:then_(nil, print)
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--- BIG TESTS
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function test()
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return Promise.new(function(resolve, reject)
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local value = math.random() -- imagine this was async
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if value > 0.5 then
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reject(value)
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else
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resolve(value)
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end
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end)
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end
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function do_if_passes(val)
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print("I passed!")
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print("My value was " .. tostring(val))
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end
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function do_if_fails(err)
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print("I failed!")
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print("My error was " .. tostring(err))
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end
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test():then_(do_if_passes, do_if_fails)
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]]
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