Add unit tests and simplify python wrapper for literal

Author: timsaucer

python/datafusion/expr.py

@@ -562,8 +562,6 @@ def literal(value: Any) -> Expr:
         """
         if isinstance(value, str):
             value = pa.scalar(value, type=pa.string_view())
-        if not isinstance(value, pa.Scalar):
-            value = pa.scalar(value)
         return Expr(expr_internal.RawExpr.literal(value))
 
     @staticmethod
@@ -576,7 +574,6 @@ def literal_with_metadata(value: Any, metadata: dict[str, str]) -> Expr:
         """
         if isinstance(value, str):
             value = pa.scalar(value, type=pa.string_view())
-        value = value if isinstance(value, pa.Scalar) else pa.scalar(value)
 
         return Expr(expr_internal.RawExpr.literal_with_metadata(value, metadata))
 

python/tests/test_expr.py

@@ -20,6 +20,8 @@
 from datetime import date, datetime, time, timezone
 from decimal import Decimal
 
+import arro3.core
+import nanoarrow
 import pyarrow as pa
 import pytest
 from datafusion import (
@@ -980,6 +982,34 @@ def test_literal_metadata(ctx):
         assert expected_field.metadata == actual_field.metadata
 
 
+def test_scalar_conversion() -> None:
+    expected_value = lit(1)
+    assert str(expected_value) == "Expr(Int64(1))"
+
+    # Test pyarrow imports
+    assert expected_value == lit(pa.scalar(1))
+    assert expected_value == lit(pa.scalar(1, type=pa.int32()))
+
+    # Test nanoarrow
+    na_scalar = nanoarrow.Array([1], nanoarrow.int32())[0]
+    assert expected_value == lit(na_scalar)
+
+    # Test pyo3
+    arro3_scalar = arro3.core.Scalar(1, type=arro3.core.DataType.int32())
+    assert expected_value == lit(arro3_scalar)
+
+    expected_value = lit([1, 2, 3])
+    assert str(expected_value) == "Expr(List([1, 2, 3]))"
+
+    assert expected_value == lit(pa.scalar([1, 2, 3]))
+
+    na_array = nanoarrow.Array([1, 2, 3], nanoarrow.int32())
+    assert expected_value == lit(na_array)
+
+    arro3_array = arro3.core.Array([1, 2, 3], type=arro3.core.DataType.int32())
+    assert expected_value == lit(arro3_array)
+
+
 def test_ensure_expr():
     e = col("a")
     assert ensure_expr(e) is e.expr