Why printing with glue doesn't show array element?

Why

> print("hello")
[1] "hello"

shows a [1] at the start and the string quoted, while:

> library(glue)
> print(glue("hello"))
hello

doesn't?

Glue objects have their own print method, look at print.glue()

#' @export
print.glue <- function(x, ..., sep = "\n") {
  x[is.na(x)] <- style_na(x[is.na(x)])

  if (length(x) > 0) {
    cat(x, ..., sep = sep)
  }

  invisible(x)
}

You will see that it uses cat which usually does not show the [1]. This [1] indicates the first index of a character printed to console like in print("hello").

Let's compare

I commented out the style_na part, and it gives

print.glue <- function(x, ..., sep = "\n") {
  #x[is.na(x)] <- style_na(x[is.na(x)])
  
  if (length(x) > 0) {
    cat(x, ..., sep = sep)
  }
  
  invisible(x)
}

> print.glue("Hello")
Hello
> print("Hello")
[1] "Hello"