fix use polars without library(polars)

DESCRIPTION

@@ -24,6 +24,7 @@ Suggests:
     arrow,
     bench,
     bit64,
+    callr,
     data.table,
     knitr,
     lubridate,

NEWS.md

@@ -12,6 +12,7 @@
 - New lazy function translated: `concat_str()` to concatenate several columns
   into one (#349).
 - New stat functions `pl$cov()`, `pl$rolling_cov()` `pl$corr()`, `pl$rolling_corr()` (#351).
+- Fix bug to allow using polars without library(polars) (#355).
 
 # polars 0.7.0
 

R/extendr-wrappers.R

@@ -67,6 +67,8 @@ test_print_string <- function(s) invisible(.Call(wrap__test_print_string, s))
 
 test_robj_to_expr <- function(robj) .Call(wrap__test_robj_to_expr, robj)
 
+test_wrong_call_pl_lit <- function(robj) .Call(wrap__test_wrong_call_pl_lit, robj)
+
 RPolarsErr <- new.env(parent = emptyenv())
 
 RPolarsErr$new <- function() .Call(wrap__RPolarsErr__new)

src/rust/src/rlib.rs

@@ -270,6 +270,11 @@ fn test_robj_to_expr(robj: Robj) -> RResult<Expr> {
     robj_to!(Expr, robj)
 }
 
+#[extendr]
+fn test_wrong_call_pl_lit(robj: Robj) -> RResult<Robj> {
+    Ok(R!("pl$lit({{robj}})")?) // this call should have been polars::pl$lit(...
+}
+
 extendr_module! {
     mod rlib;
     fn concat_df;
@@ -302,4 +307,5 @@ extendr_module! {
     fn test_robj_to_u32;
     fn test_print_string;
     fn test_robj_to_expr;
+    fn test_wrong_call_pl_lit;
 }

src/rust/src/utils/mod.rs

@@ -637,18 +637,18 @@ fn internal_rust_wrap_e(robj: Robj, str_to_lit: bool) -> RResult<Robj> {
     };
     match robj.rtype() {
         ExternalPtr if robj.inherits("Expr") => Ok(robj),
-        ExternalPtr if robj.inherits("WhenThen") | robj.inherits("WhenThenThen") => {
-            unpack(R!("polars:::result({{robj}}$otherwise(pl$lit(NULL)))"))
-        }
+        ExternalPtr if robj.inherits("WhenThen") | robj.inherits("WhenThenThen") => unpack(R!(
+            "polars:::result({{robj}}$otherwise(polars::pl$lit(NULL)))"
+        )),
         ExternalPtr if robj.inherits("When") => {
             rerr().plain("Cannot use a When-statement as Expr without a $then()")
         }
         _h @ Logicals | _h @ List | _h @ Doubles | _h @ Integers => {
-            unpack(R!("polars:::result(pl$lit({{robj}}))"))
+            unpack(R!("polars:::result(polars::pl$lit({{robj}}))"))
         }
-        _ if str_to_lit => unpack(R!("polars:::result(pl$lit({{robj}}))")),
+        _ if str_to_lit => unpack(R!("polars:::result(polars::pl$lit({{robj}}))")),
 
-        _ => unpack(R!("polars:::result(pl$col({{robj}}))")),
+        _ => unpack(R!("polars:::result(polars::pl$col({{robj}}))")),
     }
 }
 

tests/testthat/test-without_library_polars.R

@@ -0,0 +1,23 @@
+test_that("without library(polars)", {
+  # calling sort("mpg") triggers rust to call pl$lit() which will be available even though
+  # polars is not added to serach with search() library(polars)
+  skip_if_not_installed("callr")
+  # positive test:
+  # Will work because robj_to! now calls polars::pl$lit and polars::pl$col
+  expect_identical(
+    callr::r(\() {
+      polars::pl$DataFrame(mtcars)$sort("mpg")$to_list()
+    }),
+    polars::pl$DataFrame(mtcars)$sort("mpg")$to_list()
+  )
+
+  # Negative control:
+  # This will fail because test_wrong_call_pl_lit just uses pl$col and pl$lit
+  expect_false(
+    callr::r(\() polars:::test_wrong_call_pl_lit(42) |> polars:::is_ok())
+  )
+
+  # Positive-Negative control
+  # This works because library(polars) puts polars in search()
+  expect_true(polars:::test_wrong_call_pl_lit(42) |> polars:::is_ok())
+})