{Refactor} Remove unnecessary cli_ctx reference

[jiasli]

Description

Remove unnecessary cli_ctx reference, which makes pytest --capture=no fail:

RecursionError: maximum recursion depth exceeded

Root cause

When pytest captures stdout,

1. pytest uses io.FileIO to patch sys.stdout
2. When initializing CLI, CLI.out_file points to io.FileIO object
   

   knack/knack/cli.py

   Line 33 in 0d0308b

   out_file=sys.stdout,

3. tests.util.redirect_io uses io.StringIO to patch sys.stdout, but this doesn't affect the existing CLI.out_file

Since CLI.out_file doesn't equal sys.__stdout__ (the original stdout), it won't be replaced with a colorama.ansitowin32.StreamWrapper:

knack/knack/cli.py

Lines 195 to 197 in 0d0308b

	if self.out_file == sys.__stdout__:
	# point out_file to the new sys.stdout which is overwritten by colorama
	self.out_file = sys.stdout

As PreviewItem (same for ExperimentalItem and Deprecated) keeps a reference to cli_ctx, during invocation

knack/knack/commands.py

Line 353 in fe3bf5d

command_kwargs = copy.deepcopy(self.group_kwargs)

1. PreviewItem is deepcopied ->
2. cli_ctx is deepcopied ->
3. CLI.out_file is deepcopied

Because io.FileIO can't be pickled, copy.deepcopy fails and reaches

knack/knack/util.py

Lines 78 to 82 in 5f0bcc2

	except TypeError:
	if k == 'cli_ctx':
	setattr(result, k, self.cli_ctx)
	else:
	raise

This makes cli_ctx not being deepcopied.

However, when pytest is called with pytest --capture=no, it doesn't patch sys.stdout,

1. When initializing CLI, CLI.out_file equals sys.__stdout__
2. tests.util.redirect_io uses io.StringIO to patch sys.stdout, but this doesn't affect the existing CLI.out_file

Since CLI.out_file equals sys.__stdout__ (the original stdout), it will be replaced with a colorama.ansitowin32.StreamWrapper and be deepcopied.

Because of a circular reference in AnsiToWin32

https://github.com/tartley/colorama/blob/3d8d48a95de10be25b161c914f274ec6c41d3129/colorama/ansitowin32.py#L28-L29

    def __getattr__(self, name):
        return getattr(self.__wrapped, name)

and io.StringIO can be pickled, when self.__wrapped is not set, deepcopy fails with exception RecursionError: maximum recursion depth exceeded.

To repro, use this simple script:

import colorama
import copy
import sys
import io

sys.stdout = io.StringIO()
colorama.init()
copy.deepcopy(sys.stdout)

Or

class StreamWrapper(object):
    def __init__(self, wrapped, converter):
        # self.__wrapped = wrapped
        self.__convertor = converter

    def __getattr__(self, name):
        return getattr(self.__wrapped, name)


sr = StreamWrapper("a", "b")
hasattr(sr, '__setstate__')