Stop using config at import

[leotrs]

Context

This PR belongs to the ongoing refactor of the config system (#337).

Main change

The main goal here is to use the config dict as little as possible during library initialization. After this PR, config is only being used by a class/instance after the library has been imported (and thus after all other classes/functions/variables are already defined).

The motivation

The current state of the codebase contains a lot of CONFIG dictionaries as class attributes. Some of these have keys that are set using the value of the global config dict. Since all classes (and therefore all class attributes) are defined as soon as the library is being imported, all of the CONFIG attributes contain keys that are set to the values of config at the time when the library is first imported. This means that if a user/dev tries to change the config in the middle of a python session (for example, to perform tests), the CONFIG attributes will not reflect those changes. This is Bad. This PR changes the Bad to Good.

List of changes

• Most of the changes involve moving some keys from CONFIG to the __init__ method of the class.
• I also added the tests/test_coordinate_system.py tests. I chose the CoordinateSystem class to be tested because its CONFIG is being changed by this PR in a way that interacts with inheritance in non-trivial ways. The tests pass so I'm happy.

Future work

I believe this will be fine in terms of moving to attrs. Most of the attributes now defined in __init__ can easily be defined in __post__init__ or whatever it is.

NOTE: whoever merges this, please make sure to squash and delete all of the "merge X into Y" messages from the final commit....

[leotrs]

@huguesdevimeux @Aathish04 the tests/test_coordinate_system.py contains an example of how to use tempconfig to change the config for tests. What do you think about this? This does not yet mean we can choose a config file from the test suite, but it's getting closer. I think the next PR in this series (or the one after it...) will allow us to do so.

[Aathish04]

the tests/test_coordinate_system.py contains an example of how to use tempconfig to change the config for tests. What do you think about this? This does not yet mean we can choose a config file from the test suite, but it's getting closer. I think the next PR in this series (or the one after it...) will allow us to do so.

I think this'll clear up a lot of confusion regarding exactly what config is used for which test. Eagerly awaiting the PR!

[huguesdevimeux]

Very good. One step more against CONFIG !