[Feature Request] Allow dots in injected Expr function names

[polds]

We'd like to inject effectively an entire package into our Expr environment with a dozen or so methods. We were hoping to be able to effectively treat it like Go's package syntax and do something like:

expr.Function("pkg.NewThing", func(p ...any) (any, error) { }

But pkg. seems disallowed as the Compile step throws an error like:

unknown name pkg (1:9)
| let x = pkg.NewThing([1, 2, 3]); x.String()
| ........^

[antonmedv]

What about adding a variable containing a struct with all needed methods?

type Pkg struct{}

func (p Pkg) NewThing(a, b int) int {
	return a + b
}

func main() {
	env := map[string]interface{}{
		"pkg": Pkg{},
	}

	program, err := expr.Compile(`pkg.NewThing(1, 2)`, expr.Env(env))
}

[polds]

I was hoping to avoid touching the passed in Env where sometimes we're passing around concrete types and not just a map[string]any, but that would work.

[antonmedv]

I see. This is actually a good point. in case you’re passing extract as it’s not possible always to add additional methods

Let me think for an api of declaring namespaces four functions

[PranavPeshwe]

I think the method that @antonmedv suggested is elegant & straightforward. I use the same.
@polds , the expr.compile/run functions could be fronted by another function which (as needed) wraps the incoming object (based on its type) and adds requisite functions (in your case a library) to a [say] wrapper.utils member which could be an array/map.

[antonmedv]

Yes, this is a good suggestion. Even if you are using a struct as an environment, it is possible to embed the struct in another struct.

type Wrapper struct {
 	MyEnv
	Pkg Pkg `expr:"pkg"`
}

type Pkg struct{}

func (p Pkg) NewThing(a, b int) int {
	return a + b
}

func main() {
	program, err := expr.Compile(`pkg.NewThing(1, 2)`, expr.Env(Wrapper{}))
}