Add method $clone() for LazyFrame (#347)

NEWS.md

@@ -2,7 +2,8 @@
 
 ## What's changed
 
-- New method `$explode()` for `DataFrame` and `LazyFrame`.
+- New method `$explode()` for `DataFrame` and `LazyFrame` (#314).
+- New method `$clone()` for `LazyFrame` (#347).
 
 # polars 0.7.0
 

R/extendr-wrappers.R

@@ -951,6 +951,8 @@ LazyFrame$schema <- function() .Call(wrap__LazyFrame__schema, self)
 
 LazyFrame$explode <- function(columns, dotdotdot_args) .Call(wrap__LazyFrame__explode, self, columns, dotdotdot_args)
 
+LazyFrame$clone_see_me_macro <- function() .Call(wrap__LazyFrame__clone_see_me_macro, self)
+
 #' @export
 `$.LazyFrame` <- function (self, name) { func <- LazyFrame[[name]]; environment(func) <- environment(); func }
 

R/lazyframe__lazy.R

@@ -947,3 +947,14 @@ LazyFrame_explode = function(columns = list(), ...) {
   .pr$LazyFrame$explode(self, columns, dotdotdot_args) |>
     unwrap("in explode():")
 }
+
+#' Clone a LazyFrame
+#'
+#' This makes a very cheap deep copy/clone of an existing `LazyFrame`.
+#' @return A LazyFrame
+#' @examples
+#' pl$LazyFrame(mtcars)$clone()
+
+LazyFrame_clone = function() {
+  .pr$LazyFrame$clone_see_me_macro(self)
+}

src/rust/src/lazy/dataframe.rs

@@ -401,6 +401,10 @@ impl LazyFrame {
         }
         Ok(self.0.clone().explode(columns).into())
     }
+
+    pub fn clone_see_me_macro(&self) -> LazyFrame {
+        self.clone()
+    }
 }
 
 #[derive(Clone)]

tests/testthat/test-lazy.R

@@ -646,3 +646,12 @@ test_that("with_row_count", {
   lf = pl$LazyFrame(mtcars)
   expect_identical(lf$with_row_count("idx", 42)$select(pl$col("idx"))$collect()$to_data_frame()$idx, as.double(42:(41+nrow(mtcars))))
 })
+
+test_that("cloning", {
+  pf = pl$LazyFrame(iris)
+
+  # deep copy clone rust side object, hence not same mem address
+  pf2 = pf$clone()
+  expect_identical(pf$collect()$to_data_frame(), pf2$collect()$to_data_frame())
+  expect_different(pl$mem_address(pf), pl$mem_address(pf2))
+})