A Python x-callback-url client for bi-directional communication with x-callback-url enabled macOS applications. python-xcall supports callbacks from appplications. It wraps the handy xcall command line tool.

• macOS
• Python 3
• Uses xcall (included).
• Needs pytest for testing

Check it out:

$ git clone https://github.com/robwalton/python-xcall.git
Cloning into 'python-xcall'...

Call a scheme (ulysses) with an action (get-version):

>>> import xcall
>>> xcall.xcall('ulysses', 'get-version')
{u'apiVersion': u'2', u'buildNumber': u'33542'}

An x-success reply will be utf-8 un-encoded, then url unquoted, and then un-marshaled using json into Python objects and returned.

A dictionary of action parameters can also be provided (each value is utf-8 encoded and then url quoted before sending):

>>> xcall.xcall('ulysses', 'new-sheet', {'text':'My new sheet', 'index':'2'})

If the application calls back with an x-error, an XCallbackError will be raised:

>>> xcall.xcall('ulysses', 'an-invalid-action')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
...
XCallbackError: x-error callback: '{
  "errorMessage" : "Invalid Action",
  "errorCode" : "100"
}
' (in response to url: 'ulysses://x-callback-url/an-invalid-action')

For more control create an instance of xcall.XCallClient, specifying the scheme to use, whether responses should be un-marshaled using json, and an x-error handler. For example:

class UlyssesError(XCallbackError):
    pass

def ulysses_xerror_handler(xerror, requested_url):
    error_message = eval(xerror)['errorMessage']
    error_code = eval(xerror)['errorCode']
    raise UlyssesError(
        ("%(error_message)s. Code=%(error_code)s. "
         "In response to sending the url '%(requested_url)s'") % locals())

ulysses_client = XCallClient(
    'ulysses', on_xerror_handler=ulysses_xerror_handler,  json_decode_success=True)

Make calls using:

>>> ulysses_client.xcall('get-version')

or just:

>>> ulysses_client('get-version')

As logger output just goes directly to the terminal, it is disabled by default. To enable more verbose logging use:

>>> import xcall
>>> xcall.enable_verbose_logging()

An attempt is made to ensure that xcall is not already running, but there is 20-30ms window in which multiple calls to this module will result in multiple xcall processes running and the chance of replies being mixed up.

Running the tests requires the pytest package. Some optional integration tests currently require Ulysses. Code your access-token into the top of test_calls.py. Obtain the access token string by removing the @skip marker from test_authorise() in test_calls.py and running the tests.

From the root package folder call:

$ pytest
...

The code and the documentation are released under the MIT and Creative Commons Attribution-NonCommercial licences, respectively.

Thanks to:

• Martin Finke for his handy xcall application
• Dean Jackson for suggestions
• @robwalton for the upstream, Python 2.7 version of this library