Question

在Transcrypt Python to JavaScript编译器中实现协同程序时，我遇到了以下奇怪的问题。

Transcrypt使用CPython 3.6的本机解析器生成AST。对于异步全局函数defs，它会生成AsyncFunctionDef节点。但对于异步方法，它没有！然而，CPython本身似乎正确地编译了异步方法。

所以下面的一段代码与CPython一起运行，但是Transcrypt无法运行它，因为CPython的AST模块生成的AST似乎缺少方法的AsyncFunctionDef节点（而不是全局函数）。

所以下面的代码不会生成AsyncFunctionDef节点：

from org.transcrypt.stubs.browser import __pragma__, __envir__

# Note that CPython will ignore all pragma's



# Provide waitAWhile for Transcrypt

__pragma__ ('js', '{}', '''
    function waitAWhile (aTime, asio) {
      return new Promise (resolve => {
        setTimeout (() => {
          resolve (aTime);
        }, 1000 * aTime);
      });
    }
''')



# Provide waitAWhile for CPython

__pragma__ ('skip') # Compile time, needed because import is done compile time

import asyncio

def waitAWhile (aTime, asio):
    return asio.sleep (aTime)

__pragma__ ('noskip')



# Actual code to be tested    

async def f (waw, asio):
    print ('f0')
    await waw (2, asio)
    print ('f1')

class C:
    def __init__ (self):
        self.aTime = 2

    async def g (self, waw, asio):
        print ('g0')
        await waw (self.aTime, asio)
        print ('g1')

c = C ()


# Just call async functions for Transcrypt, since in the browser JavaScript is event driven by default

if __envir__.executor_name == __envir__.transpiler_name:
    f (waitAWhile, None)
    c.g (waitAWhile, None)
    c.g (waitAWhile, None)
    f (waitAWhile, None)



# Create event loop and tasks for CPython, since it isn't event driven by default

else:
    eventLoop = asyncio.get_event_loop ()
    tasks = [
        eventLoop.create_task (f (waitAWhile, asyncio)),
        eventLoop.create_task (c.g (waitAWhile, asyncio)),
        eventLoop.create_task (c.g (waitAWhile, asyncio)),
        eventLoop.create_task (f (waitAWhile, asyncio)),
    ]

    waitingTasks = asyncio.wait (tasks)
    eventLoop.run_until_complete (waitingTasks)
    eventLoop.close ()

我错过了什么？异步方法是官方支持的，不是吗？在PEP 492中找不到任何具体内容。

示例的完整代码是：

mysql_fetch_assoc()

Answer 1

Eventually I got the parser to work properly. I must have blocked the parse somewhere else initially. Probably I forgot to call visit from a node higher up the tree. Unfortunaly I can't reproduce the problem anymore.

For those interested, the parser code is at:

https://github.com/QQuick/Transcrypt/blob/master/transcrypt/modules/org/transcrypt/compiler.py

line 2045.

Most important: Python's ast module works fine, although it could do with a bit more documentation.

There's a (quite compact but useable) 3rd party doc at:

https://greentreesnakes.readthedocs.io/en/latest/

Python 3.6 AST模块无法识别异步方法

1 个答案: