From 6a008e6f72b6c768cd0bfb90951570856831261b Mon Sep 17 00:00:00 2001
From: Kevin-Li-2025 <2242139@qq.com>
Date: Mon, 29 Jun 2026 14:59:24 +0800
Subject: [PATCH] Align scalar UDF return-field literal args

Signed-off-by: Kevin-Li-2025 <2242139@qq.com>
---
 .../user_defined_scalar_functions.rs          | 72 ++++++++++++++++++-
 datafusion/expr/src/expr_schema.rs            | 36 +++++++---
 2 files changed, 99 insertions(+), 9 deletions(-)

diff --git a/datafusion/core/tests/user_defined/user_defined_scalar_functions.rs b/datafusion/core/tests/user_defined/user_defined_scalar_functions.rs
index b758aeb5209e8..6d4f7948bd4d9 100644
--- a/datafusion/core/tests/user_defined/user_defined_scalar_functions.rs
+++ b/datafusion/core/tests/user_defined/user_defined_scalar_functions.rs
@@ -40,13 +40,15 @@ use datafusion_common::{
     DFSchema, DataFusionError, Result, ScalarValue, assert_batches_eq,
     assert_batches_sorted_eq, assert_contains, exec_datafusion_err, exec_err,
     not_impl_err, plan_err,
+    types::{NativeType, logical_int16},
 };
 use datafusion_expr::simplify::{ExprSimplifyResult, SimplifyContext};
 use datafusion_expr::{
     Accumulator, ColumnarValue, CreateFunction, CreateFunctionBody, LogicalPlanBuilder,
     OperateFunctionArg, ReturnFieldArgs, ScalarFunctionArgs, ScalarUDF, ScalarUDFImpl,
-    Signature, Volatility, lit_with_metadata,
+    Signature, TypeSignatureClass, Volatility, lit_with_metadata,
 };
+use datafusion_expr_common::signature::Coercion;
 use datafusion_expr_common::signature::TypeSignature;
 use datafusion_functions_nested::range::range_udf;
 use parking_lot::Mutex;
@@ -2078,6 +2080,74 @@ AS t(string, extension)
     Ok(())
 }
 
+/// https://github.com/apache/datafusion/issues/19982
+#[tokio::test]
+async fn test_return_field_args_scalar_argument_types_match_arg_fields() -> Result<()> {
+    #[derive(Debug, PartialEq, Eq, Hash)]
+    struct TestUdf {
+        signature: Signature,
+    }
+
+    impl Default for TestUdf {
+        fn default() -> Self {
+            Self {
+                signature: Signature::coercible(
+                    vec![Coercion::new_implicit(
+                        TypeSignatureClass::Native(logical_int16()),
+                        vec![TypeSignatureClass::Numeric],
+                        NativeType::Int16,
+                    )],
+                    Volatility::Immutable,
+                ),
+            }
+        }
+    }
+
+    impl ScalarUDFImpl for TestUdf {
+        fn name(&self) -> &str {
+            "test_udf"
+        }
+
+        fn signature(&self) -> &Signature {
+            &self.signature
+        }
+
+        fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
+            unreachable!("return_field_from_args is implemented")
+        }
+
+        fn return_field_from_args(&self, args: ReturnFieldArgs) -> Result<FieldRef> {
+            assert_eq!(args.arg_fields.len(), 1);
+            assert_eq!(args.scalar_arguments.len(), 1);
+            assert_eq!(
+                args.arg_fields[0].data_type(),
+                &args.scalar_arguments[0]
+                    .expect("literal argument")
+                    .data_type()
+            );
+            Ok(
+                Field::new(self.name(), args.arg_fields[0].data_type().clone(), true)
+                    .into(),
+            )
+        }
+
+        fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
+            assert!(matches!(
+                args.args[0],
+                ColumnarValue::Scalar(ScalarValue::Int16(Some(_)))
+            ));
+            Ok(args.args[0].clone())
+        }
+    }
+
+    let ctx = SessionContext::new();
+    ctx.register_udf(TestUdf::default().into());
+
+    ctx.sql("select test_udf(1)").await?.collect().await?;
+
+    Ok(())
+}
+
 /// https://github.com/apache/datafusion/issues/17422
 #[tokio::test]
 async fn test_extension_metadata_preserve_in_subquery() -> Result<()> {
diff --git a/datafusion/expr/src/expr_schema.rs b/datafusion/expr/src/expr_schema.rs
index 039bbad65a660..ac6b6d3728953 100644
--- a/datafusion/expr/src/expr_schema.rs
+++ b/datafusion/expr/src/expr_schema.rs
@@ -87,6 +87,30 @@ fn cast_output_field(
     Arc::new(f)
 }
 
+fn scalar_arguments_for_fields(
+    args: &[Expr],
+    arg_fields: &[FieldRef],
+) -> Result<Vec<Option<ScalarValue>>> {
+    args.iter()
+        .zip(arg_fields)
+        .map(|(expr, field)| {
+            literal_scalar_value(expr)
+                .map(|sv| sv.cast_to(field.data_type()))
+                .transpose()
+        })
+        .collect()
+}
+
+fn literal_scalar_value(expr: &Expr) -> Option<&ScalarValue> {
+    match expr {
+        Expr::Literal(sv, _) => Some(sv),
+        Expr::Cast(Cast { expr, .. }) | Expr::TryCast(TryCast { expr, .. }) => {
+            literal_scalar_value(expr)
+        }
+        _ => None,
+    }
+}
+
 impl ExprSchemable for Expr {
     /// Returns the [arrow::datatypes::DataType] of the expression
     /// based on [ExprSchema]
@@ -580,16 +604,12 @@ impl ExprSchemable for Expr {
                     .collect::<Result<Vec<_>>>()?;
                 let new_fields = verify_function_arguments(func.as_ref(), &fields)?;
 
-                let arguments = args
-                    .iter()
-                    .map(|e| match e {
-                        Expr::Literal(sv, _) => Some(sv),
-                        _ => None,
-                    })
-                    .collect::<Vec<_>>();
+                let arguments = scalar_arguments_for_fields(args, &new_fields)?;
+                let argument_refs =
+                    arguments.iter().map(Option::as_ref).collect::<Vec<_>>();
                 let args = ReturnFieldArgs {
                     arg_fields: &new_fields,
-                    scalar_arguments: &arguments,
+                    scalar_arguments: &argument_refs,
                 };
 
                 func.return_field_from_args(args)