Model proc-macro WIP example

[DevinR528]

One of the more interesting features of rust are proc-macro's, I have wondered if it was possible to use a diesel style "schema" generator to create the Model and by doing so create a type that can hold policy lines and have this also used in enforce possibly? This example is more a proof of concept to start a conversation about this feature.

I created a repo with a minimal-ish example Casbin-proc-macro

Questions

Is it even wanted? How would this be integrated without breaking existing code or have a simple upgrade path ? Any other thoughts

Advantages

• gives type safety to the model definition compile time errors, instead of runtime
• by reading in the model we can dynamically define the Policy struct and the function to compare a request to a policy
• no rhai this is maybe a positive not sure about the trade offs
• maybe others?

[PsiACE]

Hi, I saw your work and it was great. Just wondering, what do you think is the necessity of this approach at this stage?

Since you mentioned diesel, I have some other ideas. For example

• A configuration file like casbin.toml;
• Some mechanisms like migrations.
• Of course, the schema you mentioned is also an important part.

[DevinR528]

what do you think is the necessity of this approach at this stage?

It would move a lot of code from runtime to being compile time checked. Removing the rhai eval would improve performance considerably. It isn't a necessity but it would be nice, as everything works now. I do think using something like the casbin-proc-macro example would allow for easy migrations and Model schema generation.

[GopherJ]

@DevinR528 I think some day we really need a modeling language for casbin so that things can be verified and validated and converted to the correct format.