feat: consolidate warning helpers and update temporal function calls

- Collapsed warning helpers into a single function `_warn_if_expr_for_literal_arg` in `python/datafusion/functions/__init__.py`.
- Updated callers of temporal functions `_date_part` and `_date_trunc` in `python/datafusion/functions/__init__.py`.
- Modified the digest behavior test in `python/tests/test_functions.py` to use native method strings.
- Updated the encode/decode behavior test to use native "base64" in `python/tests/test_functions.py`.

Author: kosiew

python/datafusion/functions/__init__.py

@@ -64,20 +64,16 @@
 from datafusion.functions import spark
 
 
-def _warn_expr_for_literal_arg(function_name: str, arg_name: str) -> None:
-    warnings.warn(
-        f"Passing Expr for {function_name}() argument {arg_name!r} is deprecated; "
-        "pass a Python literal instead.",
-        DeprecationWarning,
-        stacklevel=4,
-    )
-
-
 def _warn_if_expr_for_literal_arg(
     value: Any, function_name: str, arg_name: str
 ) -> None:
     if isinstance(value, Expr):
-        _warn_expr_for_literal_arg(function_name, arg_name)
+        warnings.warn(
+            f"Passing Expr for {function_name}() argument {arg_name!r} is deprecated; "
+            "pass a Python literal instead.",
+            DeprecationWarning,
+            stacklevel=3,
+        )
 
 
 __all__ = [
@@ -2733,8 +2729,7 @@ def date_part(part: Expr | str, date: Expr) -> Expr:
 
 
 def _date_part(part: Expr | str, date: Expr, function_name: str) -> Expr:
-    if isinstance(part, Expr):
-        _warn_expr_for_literal_arg(function_name, "part")
+    _warn_if_expr_for_literal_arg(part, function_name, "part")
     part = coerce_to_expr(part)
     return Expr(f.date_part(part.expr, date.expr))
 
@@ -2770,8 +2765,7 @@ def date_trunc(part: Expr | str, date: Expr) -> Expr:
 
 
 def _date_trunc(part: Expr | str, date: Expr, function_name: str) -> Expr:
-    if isinstance(part, Expr):
-        _warn_expr_for_literal_arg(function_name, "part")
+    _warn_if_expr_for_literal_arg(part, function_name, "part")
     part = coerce_to_expr(part)
     return Expr(f.date_trunc(part.expr, date.expr))
 

python/tests/test_functions.py

@@ -1014,7 +1014,7 @@ def test_string_functions(df, function, expected_result):
 
 def test_hash_functions(df):
     exprs = [
-        f.digest(column("a"), literal(m))
+        f.digest(column("a"), m)
         for m in (
             "md5",
             "sha224",
@@ -1602,12 +1602,10 @@ def test_regr_funcs_df(func, expected):
 
 def test_binary_string_functions(df):
     df = df.select(
-        f.encode(column("a").cast(pa.string()), literal("base64").cast(pa.string())),
+        f.encode(column("a").cast(pa.string()), "base64"),
         f.decode(
-            f.encode(
-                column("a").cast(pa.string()), literal("base64").cast(pa.string())
-            ),
-            literal("base64").cast(pa.string()),
+            f.encode(column("a").cast(pa.string()), "base64"),
+            "base64",
         ),
     )
     result = df.collect()