R - how to pass a formula to a with(data, lm(y ~ x)) construction

This question is highly related to R - how to pass formula to a with(df, glm(y ~ x)) construction inside a function but asks a broader question.

Why do these expressions work?

text_obj <- "mpg ~ cyl"form_obj <- as.formula(text_obj)with(mtcars, lm(mpg ~ cyl)) with(mtcars, lm(as.formula(text_obj))) lm(form_obj, data = mtcars)

But not this one?

with(mtcars, lm(form_obj))Error in eval(predvars, data, env) : object 'mpg' not found

I would usually use the data argument but this is not possible in the mice package.Ie.

library(mice)mtcars[5, 5] <- NA # introduce a missing value to be imputedmtcars.imp = mice(mtcars, m = 5)

These don't work

lm(form_obj, data = mtcars.imp)with(mtcars.imp, lm(form.obj))

but this does

with(mtcars.imp, lm(as.formula(text_obj)))

Thus, is it better to always thus use the as.formula argument inside the function, rather than construct it first and then pass it in?