[python/pyre.vim] Fix pyre persistent behavior

[oliverralbertini]

It's necessary to provide a -l option to pyre with the closest parent
directory containing a .pyre_configuration.local file, or simply
change directory (cwd) to the root of the pyre project. Thanks to Ken
Verbosky for the code that fixes this.

Error seen when not using such a solution:

1031.473923 on 6: Dropping message 'ƛ Background task unexpectedly quited: Invalid configuration: Cannot find any source files to analyze. Either `source_directories` or `targets` must be specified.

Issue with this approach is that if you are editing files under
different projects, the pyre persistent process is not re-created for
each file. We have to do :ALEStopAlllsps in order for the process to
start with the new working directory.

[oliverralbertini]

I'm seeing a couple of failures, but I'm not sure they're related to my change:

[00:01:44]     (5/6) [EXECUTE] (X) {'line_length': 17, 'conn_id': 347, 'source': 'ale-import', 'column': 7, 'request_id': 1, 'line': 2, 'additional_edits_only': 1, 'completion_filter': function('ale#completion#python#CompletionItemFilter'), 'prefix': 'missingword'} should be equal to {'request_id': 1, 'conn_id': 347, 'source': 'ale-import', 'column': 7, 'line_length': 17, 'line': 2, 'additional_edits_only': 1, 'completion_filter': 'ale#completion#python#CompletionItemFilter', 'prefix': 'missingword'}
[00:01:44]     (6/6) [  GIVEN] Some example Python code
[00:01:44]     (6/6) [EXECUTE] ALEImport should tell the user when no completions were found from a language server
[00:01:44]     (6/6) [EXECUTE] (X) {'line_length': 17, 'conn_id': 347, 'source': 'ale-import', 'column': 7, 'request_id': 1, 'line': 2, 'additional_edits_only': 1, 'completion_filter': function('ale#completion#python#CompletionItemFilter'), 'prefix': 'missingword'} should be equal to {'request_id': 1, 'conn_id': 347, 'source': 'ale-import', 'column': 7, 'line_length': 17, 'line': 2, 'additional_edits_only': 1, 'completion_filter': 'ale#completion#python#CompletionItemFilter', 'prefix': 'missingword'}

[hsanson]

@oliverralbertini you changed the completion_filter value in the linter definition from ale#completion#python#CompletionItemFilter to function('ale#completion#python#CompletionItemFilter') and that is why the test is failing.

Revert the change or update the tests with the new value, whichever makes the linter work properly.

[oliverralbertini]

@oliverralbertini you changed the completion_filter value in the linter definition from ale#completion#python#CompletionItemFilter to function('ale#completion#python#CompletionItemFilter') and that is why the test is failing.

Thanks @hsanson, great catch. I will just revert it, seems from the docs that it can be either a string of funcref:

  `completion_filter`     A |String| or |Funcref| for a callback function
                         accepting a buffer number and a completion item.

                         The completion item will be a |Dictionary| following
                         the Language Server Protocol `CompletionItem`
                         interface as described in the specification,
                         available online here:
                         https://microsoft.github.io/language-server-protocol

[hsanson]

Thanks, looks good.