Dependencies: update to flask~=2.0 for rest extra

[sphuber]

This major version of flask has been out for close to a year and
our docs build started failing due to itsdangerous having removed
the json module that the old flask was still using

Propose to supdersede #5365

[chrisjsewell]

https://itsdangerous.palletsprojects.com/en/2.1.x/changes/#version-2-0-0

Simplejson is no longer used if it is installed. To use a different library, pass it as Serializer(serializer=...)

This seems relevant, since we use simplejson for encoding/decoding to the database. Can you check

[chrisjsewell]

I would suggest using 2.1.0, since that is the latest release

[sphuber]

I only see 2.03 on PyPI

[chrisjsewell]

Yeh that's ok, I was confusing myself with the itsdangerous version.
I think that version should also be updated here though

[sphuber]

Updated

[chrisjsewell]

This is the corresponding change in flask:

JSON support no longer uses simplejson. To use another JSON module, override app.json_encoder and json_decoder. :issue:3555

https://github.com/pallets/flask/blob/main/CHANGES.rst

[sphuber]

Looking at [552c626] the use of simplejson was added to provide consistency between Python 2 and Python 3. I would actually be tempted to investigate if this is still needed and actually try to drop the requirement and use the built-in json package. (Edit: since itsdangerous also drops Python 2 support in v2.0, they probably had a similar reason for having a custom json implementation)

But that is irrelevant for this change in this PR I think. Flask is only used for the REST API and we shouldn't care if they use a different JSON package underneath, do we?

[chrisjsewell]

if this is still needed and actually try to drop the requirement and use the built-in json package.

I believe there may be differences in encoding certain things like numpy nan/inf and Decimal (see e.g. #4964)

[sphuber]

I believe there may be differences in encoding certain things like numpy nan/inf and Decimal (see e.g. #4964)

I don't think aiida.common.json is involved in this process of serializing node content to the database though. The attributes and extras are passed through aiida.orm.implementation.utils.clean_value but that doesn't actually do JSON serialization directly. It does a manual conversion of certain types and the final serialization to JSON is left to the backend, so PostgreSQL in our case through the JSONB fields. The aiida.common.json is really only used by AiiDA when writing files to disk, or the file repository.

[chrisjsewell]

I don't think aiida.common.json is involved in this process of serializing node content to the database though

aiida-core/aiida/backends/sqlalchemy/utils.py

Lines 51 to 58 in da5f9b0

	return create_engine(
	engine_url,
	json_serializer=json.dumps,
	json_deserializer=json.loads,
	future=True,
	encoding='utf-8',
	**config.get('engine_kwargs', {}),
	)

[sphuber]

I don't think aiida.common.json is involved in this process of serializing node content to the database though

aiida-core/aiida/backends/sqlalchemy/utils.py

Lines 51 to 58 in da5f9b0

	return create_engine(
	engine_url,
	json_serializer=json.dumps,
	json_deserializer=json.loads,
	future=True,
	encoding='utf-8',
	**config.get('engine_kwargs', {}),
	)

I stand corrected 😅 Still point is not relevant for this discussion on flask and its use in the REST API, is it?

[chrisjsewell]

Still point is not relevant for this discussion on flask and its use in the REST API, is it?

No idea 🤷‍♂️, just wanted to note it as a possible source of change, e.g. if something gets deserialised from the database, with simplejson, then flask tries to "re-serialise" it with json.
Again though, I'm not particularly precious about the rest code, because I want to eventually completely replace it anyway (with aiida-restapi)