Fastest way to register namespaces programatically

I'm building a function that uses getAnywhere() to retrieve the different packages from which a given function can be exported.

Unfortunately, getAnywhere() is limited to functions that exist in a loaded namespace, so I need to register the one I use.

Time is a constraint here, as loading a lot of namespaces can be a bit long (>10s), so using library() or require() is not realistic.

In RStudio, simply printing a prefixed function is enough to register the whole namespace without loading the library:

getAnywhere("align")$where
#> character(0)

flextable::as_flextable
#> function (x, ...) 
#> {
#>     UseMethod("as_flextable")
#> }
#> <bytecode: 0x000000002158e7f0>
#> <environment: namespace:flextable>

getAnywhere("align")$where
#> [1] "namespace:xtable"    "namespace:flextable"

pkgload::unload("flextable")
getAnywhere("align")$where
#> [1] "namespace:xtable"

^{Created on 2023-06-29 with reprex v2.0.2}

As you can see:

• at first, no loaded namespace contain a function named "align"
• after printing any function from flextable, xtable and flextable are stated (xtable is a dependency of flextable)
• for the example, after unloading flextable, only xtable remains

This seems fast enough, but it is hard-coded.

How could I register the flextable namespace programmatically (along with others)?
Is there an even faster way to do so?

If you don't need to use functions from existing packages, you can use use attach()/detach() to quickly put things on and off the search path

getAnywhere("align")$where
# character(0)
x <- list(align=function() 1)
attach(x)
getAnywhere("align")$where
# [1] "x"
detach(x)
getAnywhere("align")$where
# character(0)

Actually, there is a fast little function obviously named base::loadNamespace(). Don't know how I missed it...

getAnywhere("align")$where
#> character(0)
loadNamespace("flextable")
#> <environment: namespace:flextable>
getAnywhere("align")$where
#> [1] "namespace:xtable"    "namespace:flextable"

^{Created on 2023-06-30 with reprex v2.0.2}