Better way to deal with namespace when using glue::glue

Question

I want to create a function that itself uses the awesome glue::glue function.

However, I came to find myself dealing with some namespace issue when I want to glue a variable that exists in both function and global environments:

x=1

my_glue <- function(x, ...) {
    glue::glue(x, ...)
}
my_glue("foobar x={x}") #not the expected output
# foobar x=foobar x={x}

I'd rather keep the variable named x for package consistency.

I ended up doing something like this, which works pretty well so far but only postpone the problem (a lot, but still):

my_glue2 <- function(x, ...) {
    x___=x; rm(x)
    glue::glue(x___, ...)
}
my_glue2("foobar x={x}") #problem is gone!
# foobar x=1
my_glue2("foobar x={x___}") #very unlikely but still...
# foobar x=foobar x={x___}

Is there a better/cleaner way to do this?

But you are nowhere passing the value `x = 1` in the function. How do you expect it to get into the function? Why not pass it is a separate parameter? — Ronak Shah, Mar 08 '20 at 10:58
You are right this wasnt clear. I want my function to always use the x variable of the calling envir, never the x argument holding the whole string — Dan Chaltiel, Mar 08 '20 at 11:04

Ronak Shah · Accepted Answer · 2020-03-08T12:19:12.740

2

Since the value x = 1 is nowhere passed to the function, in the current scenario a way to do this would be to evaluate the string in the global environment itself where the value of x is present before passing it to the function.

my_glue(glue::glue("foobar x={x}"))
#foobar x=1

my_glue(glue::glue("foobar x={x}"), " More text")
#foobar x=1 More text

Another option (and I think this is the answer that you are looking for) is to get the value of x from the parent environment. glue has .envir parameter, where the environment to evaluate the expression can be defined.

my_glue <- function(x, ...) {
   glue::glue(x, ...,.envir = parent.frame())
}
my_glue("foobar x={x}")
#foobar x=1

edited Mar 08 '20 at 12:19

answered Mar 08 '20 at 11:04

Ronak Shah

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I think you would want to use `.envir = parent.frame()` instead of hardcoding the `.GlobalEnv` – Tyler Smith Mar 08 '20 at 11:30
@TylerSmith yes, a better option. Updated the answer. – Ronak Shah Mar 08 '20 at 12:19
Awesome, thanks. Indeed, the first option is not what I'm looking for and makes the whole function quite useless. I'm quite surprised though, isn't `.envir = parent.frame()` the default in `glue`? – Dan Chaltiel Mar 08 '20 at 18:28
Yeah, I thought the same initially hence I hard-coded `.GlobalEnv`. Turns out it isn't how it works. Strange. – Ronak Shah Mar 08 '20 at 22:43

Better way to deal with namespace when using glue::glue

1 Answers1