From be1092ce7dafd5ba0f0eca773a7bdc16a4eabd1c Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Fri, 4 Aug 2023 10:19:32 +0200
Subject: [PATCH] Add method `$clone()` for `LazyFrame` (#347)

---
 NEWS.md                        |  3 ++-
 R/extendr-wrappers.R           |  2 ++
 R/lazyframe__lazy.R            | 11 +++++++++++
 man/LazyFrame_clone.Rd         | 17 +++++++++++++++++
 src/rust/src/lazy/dataframe.rs |  4 ++++
 tests/testthat/test-lazy.R     |  9 +++++++++
 6 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 man/LazyFrame_clone.Rd

diff --git a/NEWS.md b/NEWS.md
index 43a77589a..266116115 100644
--- a/NEWS.md
+++ b/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
 
diff --git a/R/extendr-wrappers.R b/R/extendr-wrappers.R
index 4d3f23af9..bf7c0336f 100644
--- a/R/extendr-wrappers.R
+++ b/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 }
 
diff --git a/R/lazyframe__lazy.R b/R/lazyframe__lazy.R
index 2acd0d6b5..c5b318db9 100644
--- a/R/lazyframe__lazy.R
+++ b/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)
+}
diff --git a/man/LazyFrame_clone.Rd b/man/LazyFrame_clone.Rd
new file mode 100644
index 000000000..46f990824
--- /dev/null
+++ b/man/LazyFrame_clone.Rd
@@ -0,0 +1,17 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/lazyframe__lazy.R
+\name{LazyFrame_clone}
+\alias{LazyFrame_clone}
+\title{Clone a LazyFrame}
+\usage{
+LazyFrame_clone()
+}
+\value{
+A LazyFrame
+}
+\description{
+This makes a very cheap deep copy/clone of an existing \code{LazyFrame}.
+}
+\examples{
+pl$LazyFrame(mtcars)$clone()
+}
diff --git a/src/rust/src/lazy/dataframe.rs b/src/rust/src/lazy/dataframe.rs
index 7f935c5da..ea875b77e 100644
--- a/src/rust/src/lazy/dataframe.rs
+++ b/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)]
diff --git a/tests/testthat/test-lazy.R b/tests/testthat/test-lazy.R
index 2afd5da37..20d0c1f9f 100644
--- a/tests/testthat/test-lazy.R
+++ b/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))
+})