Behavior of OmegaConf.update changed in 2.0.2rc1

[JackEngelmann]

Hi,

the behavior of update seems to have changed. When replacing a dictionary, values aren't deleted anymore.

Minimal example in 2.0.1: (property "c" is removed)

>>> conf = omegaconf.OmegaConf.create({ "a": 2, "b": { "c": 3 }})
>>> omegaconf.OmegaConf.update(conf, "b", { "d": 4 })
>>> conf
{'a': 2, 'b': {'d': 4}}

The same example in 2.0.2rc1: (property "c" is not removed)

>>> conf = omegaconf.OmegaConf.create({ "a": 2, "b": { "c": 3 } })
>>> omegaconf.OmegaConf.update(conf, "b", { "d": 4 })
>>> conf
{'a': 2, 'b': {'c': 3, 'd': 4}}

Is this a bug or an intended change?

[omry]

Thanks for letting me know this bit you.

This is an intended change. the behavior of updating dictionaries changed from replace to merge.
The behavior of update for dictionaries and lists was not well defined and the current behavior prevented some very powerful interactions with Structured Configs.

Do you have a use case where you prefer assignment over merging?

[JackEngelmann]

Ah ok, thank you for your reply!

This could be a breaking change for some people (like me :D ), so maybe a major release would be good.
My use-case is basically just deleting parts of the configuration. Is there another way to do this?

(Specifically, our configuration has { "remote_datasets": ..., "local_datasets": ... }. A script downloads the remote_datasets and adds them to the "local_datasets". The "remote_datasets" are deleted then.)

[omry]

Yeah, I agree.
The reason I felt this was okay was this was untested and undocumented behavior.
I can maintain backward compatibility by introducing a flag.

I do think the correct interpretation is to merge the dict and not to update it though, but the default behavior should not change without a warning.

[omry]

see #367