Assign value to dataframe inside parent environment - r

Question

I have a parent function (fun1) that takes data and a helper function (fun2) that operates on columns from that data. I want to assign the value from that helper function to it's matching column in data in fun1. In reality there are lots of little helper functions operating on columns and I want the value changed by fun2 to be what the other helper functions deal with.
How can I take the outout from fun2 and assign it to the matching column of data in fun1? I do not want to make that alteration to data in fun1 but want to change data from within fun2.
fun1 <- function(data){
Map(fun2, data, colnames(data))
data[[1]]
}
fun2 <- function(x, colname_x){
x <- x * 2
# my attempt to assign to `data[["mpg"]]`
assign(sprintf("data[[\"%s\"]]", colname_x), value=x, pos = 1)
}
fun1(mtcars[1:3])
Desired output of fun1:
## [1] 42.0 42.0 45.6 42.8 37.4 36.2 28.6 48.8 45.6 38.4 35.6 32.8 34.6 30.4 20.8
## [16] 20.8 29.4 64.8 60.8 67.8 43.0 31.0 30.4 26.6 38.4 54.6 52.0 60.8 31.6 39.4
## [31] 30.0 42.8
EDIT: Also tried:
fun2 <- function(x, colname_x = "mpg"){
x <- x * 2
assign(sprintf("data[[\"%s\"]]", colname_x), value=x, env = parent.frame(3))
}
Edit 2 This works but seems not so clean:
'
fun2 <- function(x, colname_x = "mpg"){
x <- x * 2
data <- get('data', env=parent.frame(3))
data[[colname_x]] <- x
assign('data', value=data, env = parent.frame(3))
}