AttributeError: 'Promise' object has no attribute 'exited'

[shvechikov]

I'm trying to run a trivial example of asynchronous execution:
run("sleep 1", asynchronous=True)

I'm getting the following traceback:

[ins] In [2]: run("sleep 1", asynchronous=True)
Out[2]: ---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
/usr/local/lib/python3.7/site-packages/IPython/core/formatters.py in __call__(self, obj)
    700                 type_pprinters=self.type_printers,
    701                 deferred_pprinters=self.deferred_printers)
--> 702             printer.pretty(obj)
    703             printer.flush()
    704             return stream.getvalue()

/usr/local/lib/python3.7/site-packages/IPython/lib/pretty.py in pretty(self, obj)
    400                         if cls is not object \
    401                                 and callable(cls.__dict__.get('__repr__')):
--> 402                             return _repr_pprint(obj, self, cycle)
    403
    404             return _default_pprint(obj, self, cycle)

/usr/local/lib/python3.7/site-packages/IPython/lib/pretty.py in _repr_pprint(obj, p, cycle)
    695     """A pprint that just redirects to the normal repr function."""
    696     # Find newlines and replace them with p.break_()
--> 697     output = repr(obj)
    698     for idx,output_line in enumerate(output.splitlines()):
    699         if idx:

/usr/local/lib/python3.7/site-packages/invoke/runners.py in __repr__(self)
   1466         # represents
   1467         template = "<Result cmd={!r} exited={}>"
-> 1468         return template.format(self.command, self.exited)
   1469
   1470     @property

AttributeError: 'Promise' object has no attribute 'exited'

I'm able to reproduce it on both MacOS 10.15.4 + Python 3.7.5 and Ubuntu 16.04.4 + Python 3.7.1

(Relates to #682 feature).

[shvechikov]

After a quick debug session I see that execution itself works fine. The issue relates to an API inconsistency:

• Promise is a Result subclass
• it doesn't call super().__init__() so self.exited is never initialized
• base __repr__() method still relies on self.exited

@bitprophet I would able to propose a fix for the issue but I don't have enough context on your plans about this API. I would drop direct inheritance here and replace it with wrapped properties (for attributes like .exited) with an explicit check that Promise is already resolved. What do you think?

[razvanioan]

No news on this yet ? It still cannot be used asynchronously ...

[elspacedoge]

I am having this issue as well...

No news on this yet ? It still cannot be used asynchronously ...

You should be able to use asynchonously, you just wont be able to display/print the returned Promise...

[Krystofee]

Printing or displaying would not be a problem, the problem is that it cannot be even waited for.

[aunsbjerg]

Just ran into this problem myself. My use case is that I have an application which consists of multiple processes that must be started individually. I want to be able to It looks something like this:

@task
def run(ctx):
    processes = []

    def _run_service(service):
        process = ctx.run(
            f"./{service}",
            asynchronous=True,
            out_stream=sys.stdout,
            err_stream=sys.stderr,
            pty=True,
        )

        if not process.ok:
            sys.exit(process.return_code)

        processes.append(process)

    for service in services:
        _run_service(service, log_level)

    for process in processes:
        process.join()

The problem is as has been mentioned before in this thread, that Promise inherits from Result but does not call the init function of Result so exited is never initialized and the code cannot run.

[Hermanoid]

Putting the workaround in clearer terms for the populace:

The failing reference to self.exited only exists under Result.__repr__, which is only called when an interactive python session asks for a nice representation of the Promise object. If you avoid asking for it, everything works.

For example, this breaks (at least if you run it in an interactive REPR session):

connection.run("sleep 1", asynchronous=True)

But this works just fine:

result = connection.run("sleep 1", asynchronous=True)
print(result.join())