fix: field_index is incorrect in RBAC with domains mode (#345)

[truc0]

Short description

get_all_named_{things} functions (things can be actions, subjects, roles) uses hard-coded index for getting "things" from policies, which causes wrong result when using RBAC with domains mode (which a new field domain is inserted to the index 1).

The PR does:

• use Model.get_field_index for getting correct field index when getting the actions, subjects
• a new testcase is added

Details

The root cause

get_all_named_{things} functions (things can be actions, subjects, roles) use fixed field index while fetching the corresponding resources, which causes incorrect behavior when the field indexes change.

According to the documentation, the RBAC mode with domains have the convenient putting domain as the second param of a policy, while the subject is located at the second param (field_index=1) in other mode.

Note: Conventionally, the domain token name in policy definition is dom and is placed as the second token (sub, dom, obj, act).

Solution of this PR

To make pycasbin works correctly, the field_index of "things"(actions, subjects, roles) should be determined from the config file (instead of hard-coded). The Model.get_field_index method is used in this PR for getting correct index from config.

What's more

Changes to documentation

Now pycasbin can detect the position of dom and act, there's no need to explicitly set the field index of dom using set_field_index API.

Similar situation

Now get_all_named_roles is still using hard-coded field index (but it won't fail in RBAC with domains mode), this can be optimized using similar API.

Close #345

[casbin-bot]

@Nekotoxin please review

[CLAassistant]

All committers have signed the CLA.

[hsluoyz]

@leeqvip plz review

[github-actions]

🎉 This PR is included in version 1.36.2 🎉

The release is available on:

• v1.36.2
• GitHub release

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