DeprecationWarning: ShellWidget._syntax_style_changed is deprecated in traitlets 4.1: use @observe and @unobserve instead

[juliangilbey]

I received the following warning when running the test suite:

spyder/plugins/ipythonconsole/tests/test_ipythonconsole.py::test_banners
  <<<PACKAGEDIR>>>/spyder/plugins/ipythonconsole/widgets/shell.py:789: DeprecationWarning: ShellWidget._syntax_style_changed is deprecated in traitlets 4.1: use @observe and @unobserve instead.
    def _syntax_style_changed(self):

[steff456]

Hi @juliangilbey,

Did you installed all the dependencies for the test suite?

[juliangilbey]

Yes I have, at least as far as I know; and this does not appear to be a dependency warning or error. I have traitlets 5.0.5 installed.

I don't know enough about traitlets or what magic it does to properly diagnose this issue. But spyder/plugins/ipythonconsole/plugin.py imports from traitlets, which presumably has an impact on lots of things. The particular code in traitlets.py that raises this warning is in the function _notify_observers and reads:

        # Now static ones
        magic_name = '_%s_changed' % name
        if event.type == "change" and hasattr(self, magic_name):
            class_value = getattr(self.__class__, magic_name)
            if not isinstance(class_value, ObserveHandler):
                _deprecated_method(class_value, self.__class__, magic_name,
                    "use @observe and @unobserve instead.")

So it seems that the name of this function, _syntax_style_changed is triggering this traitlets warning: if the name of the function is designed to invoke a traitlets behaviour, then it's not been correctly configured or something like that, and if it's not, then the name of the function should be changed.

But I may be talking nonsense.

[steff456]

In my environment I have trailets version 5.0.5, can you update that dependency to see if this fixes the warning?

[juliangilbey]

I too have traitlets version 5.0.5.

[juliangilbey]

FYI: I'm still getting this warning when running the tests in spyder 5.2.0:

spyder/plugins/ipythonconsole/tests/test_ipythonconsole.py::test_conda_env_activation
  /home/jdg/debian/spyder-packages/spyder/build-area/spyder-5.2.0+dfsg1/spyder/plugins/ipythonconsole/widgets/shell.py:931: DeprecationWarning: ShellWidget._syntax_style_changed is deprecated in traitlets 4.1: use @observe and @unobserve instead.
    def _syntax_style_changed(self):

[dalthviz]

Maybe the reimplementation over the Spyder side of _syntax_style_changed (originally defined at QtConsole: https://github.com/jupyter/qtconsole/blob/fa1a7f898e7d402ac9bb64a652db5dc509e1f649/qtconsole/jupyter_widget.py#L594-L595) also needs to be decorated with @observe('syntax_style') (and checking seems like over the Spyder side the kwarg is missing). Could you check if that helps @juliangilbey ? Thanks!

[juliangilbey]

Yes, that fixed it - well done! I'll make a PR for this.