Allow array parameters

[MattiSG]

Technical changes

• Support arrays as parameters.
• Improves wrong parameter types error message.

---

This was added to move more constants into parameters. For example, in OpenFisca-France: https://github.com/openfisca/openfisca-france/blob/master/openfisca_france/model/caracteristiques_socio_demographiques/demographie.py#L3-L35

---

TODO :

• Add Web API tests.
• Update documentation which currently states that parameters are “numeric parameters”.

[MattiSG]

CI should be fixed by #981.

[MattiSG]

Output from web-api should be checked before merging.

[MattiSG]

@benjello can you please confirm this should not damage vectorial computation performance?

[MattiSG]

I wrote the associated test in a manner decoupled from the country template, in order to avoid a repeat from #980 and in prevision of #984. However, that means discoverability from this feature will be limited in the country template.

[MattiSG]

Documentation update can be reviewed at openfisca/openfisca-doc#234.

[benjello]

@benjello can you please confirm this should not damage vectorial computation performance?

I do not see how this could damage vectorial computation. LGTM.

[MattiSG]

API output tested manually on a fork of the country template, got the following result:

{
  "description": "Array types should be allowed.",
  "id": "general.array_type",
  "metadata": {},
  "source": "https://github.com/openfisca/country-template/blob/3.12.4/openfisca_country_template/parameters/general/array_type.yaml",
  "values": {
    "2018-06-01": ["ES", "FR", "IT", "NZ"],
    "2013-01-01": ["FR"]
  }
}

Not sure about how the legislation explorer will format these results, though.

[bonjourmauko]

Any preference between typing.List and just List? Asking just for consistency (current usage is from typing import XXX, but that is not consistent with other libraries usage, for example numpy and so on).

[MattiSG]

No preference.

[bonjourmauko]

Could you use from typing import List just for consistency? Otherwise GTM :)

[bonjourmauko]

Suggested change

	load_parameter_file(path, 'array_type')
	assert load_parameter_file(path, 'array_type')

[bonjourmauko]

It will anyway pass as it is a truthy value -otherwise it would fail. Just a proposition for reader's clarity.

[bonjourmauko]

Thanks for this contribution! Looks good to me ✨

[MattiSG]

@maukoquiroga @benjello you approved this PR —thanks again! 🙂 Would you mind spending 3 minutes reviewing the associated doc update? It's really short and would avoid an outdated documentation to create confusion: openfisca/openfisca-doc#234
Thanks! 🙏

[bonjourmauko]

Thanks @MattiSG and @benjello for the review :)