Using deparse(substitute(expression) with pipe

Base Question

deparse(substitute(expression)) returns the text of the expression passed to it. However, when used after a pipe, it returns "." instead. Is it possible to somehow get the text instead?

x  <- "my variable"

expression_to_text <- function(expr) {
  expr <- deparse(substitute(expr))

# "x"

x %>% expression_to_text()
# "."

Is it possible for the piped version to also return "x"?

This stackexchange answer indirectly addresses this question (as well as the similar question "How to extract the object name when the object is piped to a function?", though it's now closed).

Instead of using deparse(substitute()), we use sys.calls(). I won't pretend to fully understand what's happening but it works for me:

x_expression <- function(x) {
  getAST <- function(ee) purrr::map_if(as.list(ee),, getAST)

  sc <- sys.calls()
  ASTs <- purrr::map( as.list(sc), getAST ) %>%
    purrr::keep( ~identical(.[[1]], quote(`%>%`)) )  # Match first element to %>%

  if( length(ASTs) == 0 ) return( enexpr(x) )        # Not in a pipe
  dplyr::last( ASTs )[[2]]    # Second element is the left-hand side

which gives the desired output, for both pipe and non-piped notation:

# mtcars

mtcars %>% x_expression()
# mtcars

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