env_binding_are_active evaluates active bindings twice

[MilesMcBain]

Probably unexpected, and prevents this function from being used over bindingIsActive.

In rlang 1.0.2:

f <- local( {
    x <- 1
    function(v) {
       if (missing(v))
           cat("get\n")
       else {
           cat("set\n")
           x <<- v
       }
       x
    }
})
makeActiveBinding("fred", f, .GlobalEnv)
rlang::env_binding_are_active(.GlobalEnv, "fred")
#> get
#> get
#> fred 
#> TRUE

^{Created on 2022-03-09 by the reprex package (v2.0.1)}

[MilesMcBain]

For clarity: evaluation should probably not occur at all, let alone twice :)

[DavisVaughan]

This seems to be because Rf_findVarInFrame3(), used by r_env_find() here, triggers active bindings.

rlang/src/rlang/env.h

Line 46 in a768b4b

r_obj* r_env_find(r_obj* env, r_obj* sym) {

[DavisVaughan]

It seems to be a feature of Rf_findVarInFrame3() to trigger active bindings. It calls BINDING_VALUE() which explicitly grabs active binding values
https://github.com/wch/r-source/blob/ac825ccbf7f7d6a7ff1dec0de17996bb1e07c775/src/main/envir.c#L1033
https://github.com/wch/r-source/blob/ac825ccbf7f7d6a7ff1dec0de17996bb1e07c775/src/main/envir.c#L119

So maybe we can just reverse the order here, look for active bindings first, then promises (because checking for promises would have triggered the active bindings). Probably worth adding a comment about the order and a test.

rlang/src/rlang/env-binding.c

Lines 23 to 29 in 6ed751b

	if (r_env_binding_is_promise(env, sym)) {
	return R_ENV_BINDING_TYPE_promise;
	}
	if (r_env_binding_is_active(env, sym)) {
	return R_ENV_BINDING_TYPE_active;
	}