query post v0.12.0 cel.Library construction

[Dan Kortschak]

Since v0.12.0 an alternative way of constructing bindings has been
available[1] and cel.Functions is now deprecated[2].

I'm going through some libs to quiet the linter warnings about the
deprecations and a question has comes up; with the new API, the
ProgramOptions method of cel.Library is no longer necessary to provide
the connections between bindings and behaviours, but there does not
appear to be any other way to bundle a set of functions into a lib
beyond the cel.Library type. Is the intended approach to just do this
```
func (lib) ProgramOptions() []cel.ProgramOption { return nil }
```
when the complete name→behaviour binding path is defined in the
CompileOptions method?

[1]https://pkg.go.dev/github.com/google/cel...@v0.15.3/cel#Function
[2]https://pkg.go.dev/github.com/google/cel...@v0.15.3/cel#Functions

[Tristan Swadell]

Hi Dan,

The `ProgramOptions()` are still useful for decorators and for turning on some specific runtime validation checks, but if you don't have any to specify just return an empty list. The code could probably be more robust and skip options which are nil, but in general the code expects a slice of size 0 or more.

func (lib) ProgramOptions() []cel.ProgramOption { return []cel.ProgramOption{} }

Cheers,

-Tristan

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[Dan Kortschak]

On Tue, 2023-05-30 at 08:42 -0700, 'Tristan Swadell' via CEL Go

Discussion Forum wrote:
> Hi Dan,
>
> The `ProgramOptions()` are still useful for decorators and for
> turning on some specific runtime validation checks, but if you don't
> have any to specify just return an empty list. The code could
> probably be more robust and skip options which are nil, but in
> general the code expects a slice of size 0 or more.
>
> func (lib) ProgramOptions() []cel.ProgramOption { return
> []cel.ProgramOption{} }
>
> Cheers,
>
> -Tristan
>

Thanks, Tristan.

From the code, a nil return should be fine. AFAICS the only call is in
func Lib(l Library) EnvOption where the return is appended to
cel.Env.progOpts, and append([]T, []T(nil)) is a valid no-op in Go.

Dan