principal

The CandidType object Principal corresponds to the Candid type principal, is inferred to be a TypeScript @dfinity/principal Principal, and will be decoded into an @dfinity/principal Principal at runtime.

TypeScript or JavaScript:

import { Canister, Principal, query } from 'azle/experimental';

export default Canister({
    getPrincipal: query([], Principal, () => {
        return Principal.fromText('rrkah-fqaaa-aaaaa-aaaaq-cai');
    }),
    printPrincipal: query([Principal], Principal, (principal) => {
        console.log(typeof principal);
        return principal;
    })
});

Candid:

service : () -> {
    getPrincipal : () -> (principal) query;
    printPrincipal : (principal) -> (principal) query;
}

dfx:

dfx canister call candid_canister printPrincipal '(principal "rrkah-fqaaa-aaaaa-aaaaq-cai")'
(principal "rrkah-fqaaa-aaaaa-aaaaq-cai")