Type eleminiation between Key, PublicKey, PrivateKey, and Subkey

[alichry]

Hey ✌️

I am facing an issue when it comes to type elimination, mainly to distinguish between a Key and Subkey instance. In earlier versions, x instanceof openpgp.Key served well. Currently, Key is no longer exported from openpgp. Therefore, we have to rely on using x instanceof openpgp.PrivateKey || x instanceof openpgp.PublicKey to check if x a primary key. However, openpgp.readKeys returns openpgp.Key[] as a type and not Array<openpgp.PublicKey | openpgp.PrivateKey>.

export const isPrivateKey = (key: openpgp.Key | openpgp.Subkey) => {
    if (key instanceof openpgp.PrivateKey || key instanceof openpgp.PublicKey) {
        return key.isPrivate();
    }
    return key.mainKey.isPrivate();
}

The above wouldn't work since we did not eliminate Key, only checked for specific derived classes of Key. If we replace the key type with openpgp.PrivateKey | openpgp.PublicKey | openpgp.Subkey, it would work well. If I want to change the types of my internal wrappers, I would have to downcast them after calling readKeys.

Are there any other approaches that would be appropriate here? Do you suggest that we tweak openpgp.readKeys's TS def and the like to return Array<openpgp.PublicKey | openpgp.PrivateKey> or type Key = openpgp.PublicKey | openpgp.PrivateKey ?

[larabr]

Hey @alichry ,
Wouldn't checking for Subkey explicitly work in your use case? e.g.

...
    if (key instanceof Subkey) {
      return key.mainKey.isPrivate();
    }
    return key.isPrivate();
}

Also, readKeys returns PublicKey[], so downcasting is only needed if you need a PrivateKey (whether we should keep exporting Key as a type is a valid question though)

[larabr]

From the type system point of view that's redundant, since you'd still have to cast the result (if you need it, you can already do const parsedKey: PrivateKey|PublicKey = await readKey(...);).

In #1347 we might switch to return a Key in the readKey(s) functions, to make it a bit clearer that you can downcast that to a PrivateKey. We are also improving support for runtime checks of the PrivateKey type (see the snippet in the description).

[alichry]

Thanks a lot 🤩 !!

[alichry]

Hey @larabr,

Subkey is not exported in index.js, hence x instanceof openpgp.Subkey would not work in this case. Any suggestions? I will implement a workaround for this locally.

Welcome to Node.js v16.2.0.
Type ".help" for more information.
> const openpgp = require('./dist/node/openpgp.min')
undefined
> openpgp.Subkey
undefined
> openpgp.SubKey
undefined
> openpgp.Key
undefined
> openpgp.PrivateKey
[class ic extends rc]
> openpgp.PublicKey
[class rc extends ec]

[larabr]

Hey @alichry , we can export Subkey. Feel free to open a PR, otherwise I can also do it soon :)

[alichry]

Say lesss, on it =)