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util/promise.lua @ 12744:e894677359e5
util.iterators: join: Work even with only a single iterator in the chain
author | Matthew Wild <mwild1@gmail.com> |
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date | Thu, 06 Oct 2022 18:34:40 +0100 |
parent | 12589:39ae08180c81 |
child | 12749:eb9814372c54 |
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local promise_methods = {}; local promise_mt = { __name = "promise", __index = promise_methods }; local xpcall = require "util.xpcall".xpcall; local unpack = table.unpack; function promise_mt:__tostring() return "promise (" .. (self._state or "invalid") .. ")"; end local function is_promise(o) local mt = getmetatable(o); return mt == promise_mt; end local function wrap_handler(f, resolve, reject, default) if not f then return default; end return function (param) local ok, ret = xpcall(f, debug.traceback, param); if ok then resolve(ret); else reject(ret); end return true; end; end local function next_pending(self, on_fulfilled, on_rejected, resolve, reject) table.insert(self._pending_on_fulfilled, wrap_handler(on_fulfilled, resolve, reject, resolve)); table.insert(self._pending_on_rejected, wrap_handler(on_rejected, resolve, reject, reject)); end local function next_fulfilled(promise, on_fulfilled, on_rejected, resolve, reject) -- luacheck: ignore 212/on_rejected wrap_handler(on_fulfilled, resolve, reject, resolve)(promise.value); end local function next_rejected(promise, on_fulfilled, on_rejected, resolve, reject) -- luacheck: ignore 212/on_fulfilled wrap_handler(on_rejected, resolve, reject, reject)(promise.reason); end local function promise_settle(promise, new_state, new_next, cbs, value) if promise._state ~= "pending" then return; end promise._state = new_state; promise._next = new_next; for _, cb in ipairs(cbs) do cb(value); end -- No need to keep references to callbacks promise._pending_on_fulfilled = nil; promise._pending_on_rejected = nil; return true; end local function new_resolve_functions(p) local resolved = false; local function _resolve(v) if resolved then return; end resolved = true; if is_promise(v) then v:next(new_resolve_functions(p)); elseif promise_settle(p, "fulfilled", next_fulfilled, p._pending_on_fulfilled, v) then p.value = v; end end local function _reject(e) if resolved then return; end resolved = true; if promise_settle(p, "rejected", next_rejected, p._pending_on_rejected, e) then p.reason = e; end end return _resolve, _reject; end local next_tick = function (f) f(); end local function new(f) local p = setmetatable({ _state = "pending", _next = next_pending, _pending_on_fulfilled = {}, _pending_on_rejected = {} }, promise_mt); if f then next_tick(function() local resolve, reject = new_resolve_functions(p); local ok, ret = xpcall(f, debug.traceback, resolve, reject); if not ok and p._state == "pending" then reject(ret); end end); end return p; end local function all(promises) return new(function (resolve, reject) local settled, results, loop_finished = 0, {}, false; local total = 0; for k, v in pairs(promises) do if is_promise(v) then total = total + 1; v:next(function (value) results[k] = value; settled = settled + 1; if settled == total and loop_finished then resolve(results); end end, reject); else results[k] = v; end end loop_finished = true; if settled == total then resolve(results); end end); end local function all_settled(promises) return new(function (resolve) local settled, results, loop_finished = 0, {}, false; local total = 0; for k, v in pairs(promises) do if is_promise(v) then total = total + 1; v:next(function (value) results[k] = { status = "fulfilled", value = value }; settled = settled + 1; if settled == total and loop_finished then resolve(results); end end, function (e) results[k] = { status = "rejected", reason = e }; settled = settled + 1; if settled == total and loop_finished then resolve(results); end end); else results[k] = v; end end loop_finished = true; if settled == total then resolve(results); end end); end local function join(handler, ...) local promises, n = { ... }, select("#", ...); return all(promises):next(function (results) return handler(unpack(results, 1, n)); end); end local function race(promises) return new(function (resolve, reject) for i = 1, #promises do promises[i]:next(resolve, reject); end end); end local function resolve(v) return new(function (_resolve) _resolve(v); end); end local function reject(v) return new(function (_, _reject) _reject(v); end); end local function try(f) return resolve():next(function () return f(); end); end function promise_methods:next(on_fulfilled, on_rejected) return new(function (resolve, reject) --luacheck: ignore 431/resolve 431/reject self:_next(on_fulfilled, on_rejected, resolve, reject); end); end function promise_methods:catch(on_rejected) return self:next(nil, on_rejected); end function promise_methods:finally(on_finally) local function _on_finally(value) on_finally(); return value; end local function _on_catch_finally(err) on_finally(); return reject(err); end return self:next(_on_finally, _on_catch_finally); end return { new = new; resolve = resolve; join = join; reject = reject; all = all; all_settled = all_settled; race = race; try = try; is_promise = is_promise; set_nexttick = function(new_next_tick) next_tick = new_next_tick; end; }