feat(python): Improve error message when passing invalid input to lit

py-polars/src/functions/lazy.rs

@@ -419,8 +419,10 @@ pub fn lit(value: &PyAny, allow_object: bool) -> PyResult<PyExpr> {
         Ok(dsl::lit(s).into())
     } else {
         Err(PyTypeError::new_err(format!(
-            "invalid literal value: {:?}",
-            value.str()?
+            "cannot create expression literal for value of type {}: {}\
+            \n\nHint: Pass `allow_object=True` to accept any value and create a literal of type Object.",
+            value.get_type().qualname()?,
+            value.repr()?
         )))
     }
 }

py-polars/tests/unit/functions/test_lit.py

@@ -87,3 +87,11 @@ def test_list_datetime_11571() -> None:
 )
 def test_lit_int_return_type(input: int, dtype: pl.PolarsDataType) -> None:
     assert pl.select(pl.lit(input)).to_series().dtype == dtype
+
+
+def test_lit_unsupported_type() -> None:
+    with pytest.raises(
+        TypeError,
+        match="cannot create expression literal for value of type LazyFrame: ",
+    ):
+        pl.lit(pl.LazyFrame({"a": [1, 2, 3]}))

py-polars/tests/unit/operations/test_with_columns.py

@@ -1,3 +1,5 @@
+import pytest
+
 import polars as pl
 from polars.testing import assert_frame_equal
 
@@ -165,3 +167,12 @@ def test_with_columns_seq() -> None:
         }
     )
     assert_frame_equal(result, expected)
+
+
+# https://github.com/pola-rs/polars/issues/15588
+def test_with_columns_invalid_type() -> None:
+    lf = pl.LazyFrame({"a": [1, 2, 3]})
+    with pytest.raises(
+        TypeError, match="cannot create expression literal for value of type LazyFrame"
+    ):
+        lf.with_columns(lf)  # type: ignore[arg-type]