Review: Async.Promise

README.md

@@ -22,6 +22,7 @@ If you are a Vim plugin author, please check this out.
 Module						 | Description
 ------------------------------------------------ | ------------------------------
 [Assertion](doc/vital/Assertion.txt)		 | assertion library
+[Async.Promise](doc/vital/Async/Promise.txt)	 | An asynchronous operation like ES6 Promise
 [Bitwise](doc/vital/Bitwise.txt)		 | bitwise operators
 [ConcurrentProcess](doc/vital/ConcurrentProcess.txt)	 | manages processes concurrently with vimproc
 [Data.Base64](doc/vital/Data/Base64.txt)	 | base64 utilities library

autoload/vital/__vital__/Async/Promise.vim

@@ -0,0 +1,257 @@
+" ECMAScript like Promise library for asynchronous operations.
+"   Spec: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise
+" This implementation is based upon es6-promise npm package.
+"   Repo: https://github.com/stefanpenner/es6-promise
+
+" States of promise
+let s:PENDING = 0
+let s:FULFILLED = 1
+let s:REJECTED = 2
+
+let s:DICT_T = type({})
+
+" @vimlint(EVL103, 1, a:resolve)
+" @vimlint(EVL103, 1, a:reject)
+function! s:noop(resolve, reject) abort
+endfunction
+" @vimlint(EVL103, 0, a:resolve)
+" @vimlint(EVL103, 0, a:reject)
+let s:NOOP = function('s:noop')
+
+" Internal APIs
+
+let s:PROMISE = {
+    \   '_state': s:PENDING,
+    \   '_children': [],
+    \   '_fulfillments': [],
+    \   '_rejections': [],
+    \   '_result': v:null,
+    \ }
+
+let s:id = -1
+function! s:_next_id() abort
+  let s:id += 1
+  return s:id
+endfunction
+
+" ... is added to use this function as a callback of timer_start()
+function! s:_invoke_callback(settled, promise, callback, result, ...) abort
+  let has_callback = a:callback isnot v:null
+  let success = 1
+  let err = v:null
+  if has_callback
+    try
+      let l:Result = a:callback(a:result)
+    catch
+      let err = {
+      \   'exception' : v:exception,
+      \   'throwpoint' : v:throwpoint,
+      \ }
+      let success = 0
+    endtry
+  else
+    let l:Result = a:result
+  endif
+
+  if a:promise._state != s:PENDING
+    " Do nothing
+  elseif has_callback && success
+    call s:_resolve(a:promise, Result)
+  elseif !success
+    call s:_reject(a:promise, err)
+  elseif a:settled == s:FULFILLED
+    call s:_fulfill(a:promise, Result)
+  elseif a:settled == s:REJECTED
+    call s:_reject(a:promise, Result)
+  endif
+endfunction
+
+" ... is added to use this function as a callback of timer_start()
+function! s:_publish(promise, ...) abort
+  let settled = a:promise._state
+  if settled == s:PENDING
+    throw 'vital: Async.Promise: Cannot publish a pending promise'
+  endif
+
+  if empty(a:promise._children)
+    return
+  endif
+
+  for i in range(len(a:promise._children))
+    if settled == s:FULFILLED
+      let l:CB = a:promise._fulfillments[i]
+    else
+      " When rejected
+      let l:CB = a:promise._rejections[i]
+    endif
+    let child = a:promise._children[i]
+    if child isnot v:null
+      call s:_invoke_callback(settled, child, l:CB, a:promise._result)
+    else
+      call l:CB(a:promise._result)
+    endif
+  endfor
+
+  let a:promise._children = []
+  let a:promise._fulfillments = []
+  let a:promise._rejections = []
+endfunction
+
+function! s:_subscribe(parent, child, on_fulfilled, on_rejected) abort
+  let a:parent._children += [ a:child ]
+  let a:parent._fulfillments += [ a:on_fulfilled ]
+  let a:parent._rejections += [ a:on_rejected ]
+endfunction
+
+function! s:_handle_thenable(promise, thenable) abort
+  if a:thenable._state == s:FULFILLED
+    call s:_fulfill(a:promise, a:thenable._result)
+  elseif a:thenable._state == s:REJECTED
+    call s:_reject(a:promise, a:thenable._result)
+  else
+    call s:_subscribe(
+         \   a:thenable,
+         \   v:null,
+         \   function('s:_resolve', [a:promise]),
+         \   function('s:_reject', [a:promise]),
+         \ )
+  endif
+endfunction
+
+function! s:_resolve(promise, ...) abort
+  let l:Result = a:0 > 0 ? a:1 : v:null
+  if s:is_promise(Result)
+    call s:_handle_thenable(a:promise, Result)
+  else
+    call s:_fulfill(a:promise, Result)
+  endif
+endfunction
+
+function! s:_fulfill(promise, value) abort
+  if a:promise._state != s:PENDING
+    return
+  endif
+  let a:promise._result = a:value
+  let a:promise._state = s:FULFILLED
+  if !empty(a:promise._children)
+    call timer_start(0, function('s:_publish', [a:promise]))
+  endif
+endfunction
+
+function! s:_reject(promise, ...) abort
+  if a:promise._state != s:PENDING
+    return
+  endif
+  let a:promise._result = a:0 > 0 ? a:1 : v:null
+  let a:promise._state = s:REJECTED
+  call timer_start(0, function('s:_publish', [a:promise]))
+endfunction
+
+function! s:_notify_done(wg, index, value) abort
+  let a:wg.results[a:index] = a:value
+  let a:wg.remaining -= 1
+  if a:wg.remaining == 0
+    call a:wg.resolve(a:wg.results)
+  endif
+endfunction
+
+function! s:_all(promises, resolve, reject) abort
+  let total = len(a:promises)
+  if total == 0
+    call a:resolve([])
+    return
+  endif
+
+  let wait_group = {
+      \   'results': repeat([v:null], total),
+      \   'resolve': a:resolve,
+      \   'remaining': total,
+      \ }
+
+  " 'for' statement is not available here because iteration variable is captured into lambda
+  " expression by **reference**.
+  call map(
+       \   copy(a:promises),
+       \   {i, p -> p.then({v -> s:_notify_done(wait_group, i, v)}, a:reject)},
+       \ )
+endfunction
+
+function! s:_race(promises, resolve, reject) abort
+  for p in a:promises
+    call p.then(a:resolve, a:reject)
+  endfor
+endfunction
+
+" Public APIs
+
+function! s:new(resolver) abort
+  let promise = deepcopy(s:PROMISE)
+  let promise._vital_promise = s:_next_id()
+  try
+    if a:resolver != s:NOOP
+      call a:resolver(
+      \   function('s:_resolve', [promise]),
+      \   function('s:_reject', [promise]),
+      \ )
+    endif
+  catch
+    call s:_reject(promise, {
+    \   'exception' : v:exception,
+    \   'throwpoint' : v:throwpoint,
+    \ })
+  endtry
+  return promise
+endfunction
+
+function! s:all(promises) abort
+  return s:new(function('s:_all', [a:promises]))
+endfunction
+
+function! s:race(promises) abort
+  return s:new(function('s:_race', [a:promises]))
+endfunction
+
+function! s:resolve(...) abort
+  let promise = s:new(s:NOOP)
+  call s:_resolve(promise, a:0 > 0 ? a:1 : v:null)
+  return promise
+endfunction
+
+function! s:reject(...) abort
+  let promise = s:new(s:NOOP)
+  call s:_reject(promise, a:0 > 0 ? a:1 : v:null)
+  return promise
+endfunction
+
+function! s:is_available() abort
+  return has('lambda') && has('timers')
+endfunction
+
+function! s:is_promise(maybe_promise) abort
+  return type(a:maybe_promise) == s:DICT_T && has_key(a:maybe_promise, '_vital_promise')
+endfunction
+
+function! s:_promise_then(...) dict abort
+  let parent = self
+  let state = parent._state
+  let child = s:new(s:NOOP)
+  let l:Res = a:0 > 0 ? a:1 : v:null
+  let l:Rej = a:0 > 1 ? a:2 : v:null
+  if state == s:FULFILLED
+    call timer_start(0, function('s:_invoke_callback', [state, child, Res, parent._result]))
+  elseif state == s:REJECTED
+    call timer_start(0, function('s:_invoke_callback', [state, child, Rej, parent._result]))
+  else
+    call s:_subscribe(parent, child, Res, Rej)
+  endif
+  return child
+endfunction
+let s:PROMISE.then = function('s:_promise_then')
+
+" .catch() is just a syntax sugar of .then()
+function! s:_promise_catch(...) dict abort
+  return self.then(v:null, a:0 > 0 ? a:1 : v:null)
+endfunction
+let s:PROMISE.catch = function('s:_promise_catch')
+
+" vim:set et ts=2 sts=2 sw=2 tw=0:

doc/vital.txt

@@ -160,6 +160,7 @@ LINKS					*Vital-links*
 
  Vital modules				*Vital-modules*
   |vital/Assertion.txt|		assertion library.
+  |vital/Async/Promise.txt|	An asynchronous operation like ES6 Promise
   |vital/Bitwise.txt|		bitwise operators.
   |vital/ConcurrentProcess.txt|	Manages processes concurrently with vimproc.
   |vital/Data/Base64.txt|	base64 utilities library.