From 4fe73a24a3027e2b97d8dc0fd667a26d1559c7e0 Mon Sep 17 00:00:00 2001
From: Weijie Guo <reswqa@163.com>
Date: Sat, 20 Jan 2024 17:31:29 +0800
Subject: [PATCH] fix(rust): Correct err message of `check_map_output_len`
 (#13854)

---
 crates/polars-lazy/src/physical_plan/expressions/apply.rs | 2 +-
 py-polars/tests/unit/operations/map/test_map_batches.py   | 8 ++++----
 py-polars/tests/unit/test_errors.py                       | 8 ++++----
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/crates/polars-lazy/src/physical_plan/expressions/apply.rs b/crates/polars-lazy/src/physical_plan/expressions/apply.rs
index 6746cd0c0272..ea664b4dafcd 100644
--- a/crates/polars-lazy/src/physical_plan/expressions/apply.rs
+++ b/crates/polars-lazy/src/physical_plan/expressions/apply.rs
@@ -285,7 +285,7 @@ fn check_map_output_len(input_len: usize, output_len: usize, expr: &Expr) -> Pol
     polars_ensure!(
         input_len == output_len, expr = expr, InvalidOperation:
         "output length of `map` ({}) must be equal to the input length ({}); \
-        consider using `apply` instead", input_len, output_len
+        consider using `apply` instead", output_len, input_len
     );
     Ok(())
 }
diff --git a/py-polars/tests/unit/operations/map/test_map_batches.py b/py-polars/tests/unit/operations/map/test_map_batches.py
index 1a2826f319c4..2cde056cc652 100644
--- a/py-polars/tests/unit/operations/map/test_map_batches.py
+++ b/py-polars/tests/unit/operations/map/test_map_batches.py
@@ -36,8 +36,8 @@ def test_error_on_reducing_map() -> None:
     with pytest.raises(
         pl.InvalidOperationError,
         match=(
-            r"output length of `map` \(6\) must be equal to "
-            r"the input length \(1\); consider using `apply` instead"
+            r"output length of `map` \(1\) must be equal to "
+            r"the input length \(6\); consider using `apply` instead"
         ),
     ):
         df.group_by("id").agg(pl.map_batches(["t", "y"], np.trapz))
@@ -47,8 +47,8 @@ def test_error_on_reducing_map() -> None:
     with pytest.raises(
         pl.InvalidOperationError,
         match=(
-            r"output length of `map` \(4\) must be equal to "
-            r"the input length \(1\); consider using `apply` instead"
+            r"output length of `map` \(1\) must be equal to "
+            r"the input length \(4\); consider using `apply` instead"
         ),
     ):
         df.select(
diff --git a/py-polars/tests/unit/test_errors.py b/py-polars/tests/unit/test_errors.py
index dda6fe590737..f6b5b2df8110 100644
--- a/py-polars/tests/unit/test_errors.py
+++ b/py-polars/tests/unit/test_errors.py
@@ -30,8 +30,8 @@ def test_error_on_reducing_map() -> None:
     with pytest.raises(
         pl.InvalidOperationError,
         match=(
-            r"output length of `map` \(6\) must be equal to "
-            r"the input length \(1\); consider using `apply` instead"
+            r"output length of `map` \(1\) must be equal to "
+            r"the input length \(6\); consider using `apply` instead"
         ),
     ):
         df.group_by("id").agg(pl.map_batches(["t", "y"], np.trapz))
@@ -40,8 +40,8 @@ def test_error_on_reducing_map() -> None:
     with pytest.raises(
         pl.InvalidOperationError,
         match=(
-            r"output length of `map` \(4\) must be equal to "
-            r"the input length \(1\); consider using `apply` instead"
+            r"output length of `map` \(1\) must be equal to "
+            r"the input length \(4\); consider using `apply` instead"
         ),
     ):
         df.select(