jonkeane commented on code in PR #13789:
URL: https://github.com/apache/arrow/pull/13789#discussion_r946522488
##########
r/R/dplyr-eval.R:
##########
@@ -121,3 +148,121 @@ format_expr <- function(x) {
}
head(out, 1)
}
+
+#' Translate a function in a given context (environment with bindings)
+#'
+#' Translates a function (if possible) with the help of existing bindings in a
+#' given environment.
+#'
+#' @param fn function to be translated
+#' @param env environment to translate against
+#'
+#' @return a translated function
+#' @keywords internal
+#' @noRd
+translate_to_arrow <- function(.fun, .env) {
+ # get the args and the body of the unknown binding
+ function_formals <- formals(.fun)
+
+ if (is.primitive(.fun)) {
+ # exit as the function can't be translated, we can only translate closures
+ stop("`", as.character(.fun[[1]]), "` is a primitive and cannot be
translated")
+ }
+
+ # TODO handle errors. `fn_body()` errors when fn is a primitive, `body()`
returns
+ # NULL so maybe we can work with that
+ function_body <- rlang::fn_body(.fun)
+
+ if (translatable(.fun, .env)) {
+ translated_function <- rlang::new_function(
+ args = function_formals,
+ body = translate_to_arrow_rec(function_body[[2]])
+ )
+ } else {
+ # TODO WIP if the function is not directly translatable, make one more try
+ # by attempting to translate the unknown calls
+ unknown_function <- setdiff(all_funs(function_body[[2]]), names(.env))
+
+ fn <- as_function(unknown_function, env = caller_env())
+ translated_function <- NULL
+ }
Review Comment:
If I'm reading this code correctly, it looks like it translates two levels
down in the function call, yeah? So if I have only functions in my function
body that have bindings it'll be fine, or if my function calls a function that
also has only functions that have bindings it'll be fine, but if my function
calls a function, which calls another function, which has only bindings it
won't work.
In other words: these will work:
```
my_func <- function(x) {
mean(x)
}
my_func_2 <- function(x) {
my_func(x)
}
```
but this one will not:
```
my_func_3 <- function(x) {
my_func_3(x)
}
```
Or does it actually recurse through the call stack?
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