[DX] plugin support at the library level

[AnomalRoil]

My use case is really that of a developer using age as a library, so with the recent age v1.1.0 release that brought official plugin support, I figured I'd start trying to use plugins. I'm starting slowly, just trying to use the Yubikey-agent plugin for now.

However, as a developer, I'm facing quite a few DX issues, which I'd love to discuss here.

My first issue is that it seems that currently the native, exported ParseIdentities method is only supporting X25519 identities:

age/parse.go

Lines 21 to 23 in 8e3f74c

	// Currently, all returned values are of type *X25519Identity, but different
	// types might be returned in the future.
	func ParseIdentities(f io.Reader) ([]Identity, error) {

Is there any specific reasons for expecting users of the library not to want plugin support?
Or maybe any guidance as to how this should happen for a library user?

Now, there are unexported methods in your main CLI package that support plugins:

age/cmd/age/parse.go

Lines 198 to 210 in 8e3f74c

	func parseIdentity(s string) (age.Identity, error) {
	switch {
	case strings.HasPrefix(s, "AGE-PLUGIN-"):
	return plugin.NewIdentity(s, pluginTerminalUI)
	case strings.HasPrefix(s, "AGE-SECRET-KEY-1"):
	return age.ParseX25519Identity(s)
	default:
	return nil, fmt.Errorf("unknown identity type")
	}
	}
	// parseIdentities is like age.ParseIdentities, but supports plugin identities.
	func parseIdentities(f io.Reader) ([]age.Identity, error) {

So I figured, sure enough, I could just copy the required code in my own codebase, but here comes my second issue:
the package plugin is currently in the age internals: "filippo.io/age/internal/plugin", which means I cannot import it to use plugin.NewIdentity in my code.

I could have tried to copy the whole plugin package in turn, but then I would have to also copy the bech32 and format ones...

I realize that plugins are basically just executed as binaries by age and so I guess I could as well just invoke the age binary directly in my code, but then it's not really acting as a library anymore.

So, what's your take on the plugin part and age as a library? It would be nice to easily have hardware token support for many use-cases.

[ngortheone]

I have exactly the same problem. I'd love to get plugin support at the library level