Passing a context to the custom functions

[schneekatze]

Hello guys,

at the moment if we want to define a custom function, we just extend the language

gval.Evaluate(
    expression,
    data,
    gval.Function("foo", func(args ...interface{}) (interface{}, error) {
	    return "bar", nil
    }),
   ...
)

Yet we can EvaluateWithContext, say context with value.

ctx := context.WithValue(context.Background(), "input", data)
gval.EvaluateWithContext(
    ctx,
    expression,
    data,
    gval.Function("foo", func(args ...interface{}) (interface{}, error) {
	    return "bar", nil
    }),
   ...
)

Unfortunately, the context is not passed into a function itself. So maybe, we could do something like

ctx := context.WithValue(context.Background(), "input", data)
gval.EvaluateWithContext(
    ctx,
    expression,
    data,
    gval.FunctionWithContext("foo", func(ctx context.Context, args ...interface{}) (interface{}, error) {
	    return count(ctx.Value("input")), nil
    }),
   ...
)

Why would one need it? E.g.:

• To get an entire parameters, not only arguments selected for the function (say, count all elements in []interface{});
• If the string is the argument, check in context, that this type should be time, parse as time and do something.

Wdyt? Or maybe there's already the way to pass some extra information into the gval function? I've tried with Init, but I apparently don't understand its concept that much.

Best regards,
sk

[schneekatze]

It's already there