PR: Refactor Spyder configuration system to use an observer pattern

[andfoy]

Description of Changes

This PR enables the Spyder configuration system to use an observer pattern in order to propagate changes across all the application actions/options/etc. This PR will supersede the current API configuration propagation logic

• Wrote at least one-line docstrings (for any new functions)
• Added unit test(s) covering the changes (if testable)

• Included a screenshot or animation (if affecting the UI, see Licecap)

Issue(s) Resolved

Fixes #

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct: @andfoy

[jitseniesen]

Thanks on tackling this area because I found the old API hard to work with. Where is the new design explained? I am lazy and don't want to search through 100+ commits and files changed. 😄

[andfoy]

@jitseniesen Basically the idea is to register any object that requires updates on a configuration option of a section via CONF.observe_configuration(observer, section, option). If the option is None, the object is notified on any change on the section. Likewise, since now we support tuple options to access nested dictionary keys, an object can subscribe to a partial tuple key. A registered object will be notified via the on_configuration_change(option, section, value) method each time a registered option/section changes via CONF.set.

This PR also introduces a decorator spyder.api.decorators.on_conf_change to register automatically methods that receive changes on specific keys, e.g.,

from spyder.config.manager import CONF
from spyder.api.decorators import on_conf_change

class ConfObserver:
    def __init__(self):
        # Register class to listen for changes in all the registered options
        for section in self._configuration_listeners:
            observed_options = self._configuration_listeners[section]
            for option in observed_options:
                CONF.observe_configuration(self, section, option)

    def on_configuration_change(self, option, section, value):
        section_recievers = self._configuration_listeners.get(section, {})
        option_recievers = section_recievers.get(option, [])
        for receiver in option_recievers:
            method = getattr(self, receiver)
            method(value)

    @on_conf_change(section='editor')
    def section_change_reciever(self, section):
          # section contains the new values of the editor section
          ...
    
    @on_conf_change(section='main_interpreter', option='custom_interpreter')
    def on_interpreter_change(self, interpreter):
          # interpreter contains the value of main_interpreter
          ...

Furthermore, to simplify things, this PR adds a new class mixin spyder.api.mixins.SpyderConfigurationObserver that already implements the aforementioned protocol. By inheriting from this mixin, the previous example can be simplified to

from spyder.api.mixins import SpyderConfigurationObserver

class ConfObserver(SpyderConfigurationObserver):
    @on_conf_change
    def this_section_change(self, value):
          # Listen for all changes in the widget `CONF_SECTION`
          # value contains the section options as a dictionary.
          ...

    @on_conf_change(section='editor')
    def section_change_reciever(self, section):
          # section contains the new values of the editor section
          ...

    @on_conf_change(option='opt')
    def on_opt_change(self, value):
          # value contains the new value of `opt` in the widget `CONF_SECTION`.
          ...

    @on_conf_change(option=['opt1', 'opt2', 'opt3'])
    def on_opts_change(self, option, value):
          # Receive multiple option change. Option will contain the option name and value, its corresponding value.
         ...

    @on_conf_change(section='section', option=['opt2', 'opt3', 'opt4', ('opt', 'nested_dict', 'value')])
    def on_section_multiple_option_change(self, option, value):
          # Recieve multiple option change from section `section`.
          ...
    
    @on_conf_change(section='main_interpreter', option='custom_interpreter')
    def on_interpreter_change(self, interpreter):
          # interpreter contains the value of main_interpreter
          ...

By default, SpyderPluginV2 and SpyderWidgetMixin classes will inherit from SpyderConfigurationObserver, making all of the new API plugins compatible with this new design. Also, all SpyderWidgetMixin will inherit its parent CONF_SECTION value, thus enabling on_conf_change to omit the section parameter to fallback to the value of CONF_SECTION.

FInally, all new actions created using self.create_action of the new API now can specify a section and option that is read and written to, thus they are also subject to the new observer pattern, where they will change their state if a change is done on the configuration option observed.

I hope this explanation is clear enough, otherwise, feel free to ask any question

[pep8speaks]

Hello @andfoy! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file spyder/api/decorators.py:

Line 26:80: E501 line too long (80 > 79 characters)

• In the file spyder/api/widgets/mixins.py:

Line 340:13: E731 do not assign a lambda expression, use a def

• In the file spyder/plugins/completion/api.py:

Line 658:1: E302 expected 2 blank lines, found 1

• In the file spyder/plugins/editor/widgets/tests/test_editor_and_outline.py:

Line 57:25: E127 continuation line over-indented for visual indent

Comment last updated at 2021-03-16 00:19:43 UTC

[ccordoba12]

Thanks @andfoy! I left an initial review for you.

[ccordoba12]

@andfoy, this is a more in-depth review for you.

[ccordoba12]

Thanks a lot @andfoy! Fantastic job with this refactoring!!