From 3f0822a85c155a8107abb9818a3c7a3be5a940c0 Mon Sep 17 00:00:00 2001
From: Andrew Lamb <andrew@nerdnetworks.org>
Date: Fri, 20 Dec 2024 22:56:06 -0500
Subject: [PATCH] Support `Signature::Any(0)`, and add tests for zero arguments

---
 .../user_defined_scalar_functions.rs          | 39 +++++++++++++++++++
 datafusion/expr-common/src/signature.rs       |  6 +++
 2 files changed, 45 insertions(+)

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 30b3c6e2bbeb3..0ce8230f7cc70 100644
--- a/datafusion/core/tests/user_defined/user_defined_scalar_functions.rs
+++ b/datafusion/core/tests/user_defined/user_defined_scalar_functions.rs
@@ -1119,6 +1119,45 @@ async fn create_scalar_function_from_sql_statement() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn test_valid_zero_argument_signatures() {
+    let signatures = vec![
+        Signature::exact(vec![], Volatility::Immutable),
+        Signature::any(0, Volatility::Immutable),
+        Signature::variadic(vec![], Volatility::Immutable),
+        Signature::variadic_any(Volatility::Immutable),
+        Signature::uniform(0, vec![], Volatility::Immutable),
+        Signature::coercible(vec![], Volatility::Immutable),
+        Signature::comparable(0, Volatility::Immutable),
+        Signature::nullary(Volatility::Immutable),
+    ];
+    for signature in signatures {
+        let ctx = SessionContext::new();
+        let udf = ScalarFunctionWrapper {
+            name: "bad_signature".to_string(),
+            expr: lit(1),
+            signature,
+            return_type: DataType::Int32,
+        };
+        ctx.register_udf(ScalarUDF::from(udf));
+        let results = ctx
+            .sql("select bad_signature()")
+            .await
+            .unwrap()
+            .collect()
+            .await
+            .unwrap();
+        let expected = vec![
+            "+-----------------+",
+            "| bad_signature() |",
+            "+-----------------+",
+            "| 1               |",
+            "+-----------------+",
+        ];
+        assert_batches_eq!(expected, &results);
+    }
+}
+
 /// Saves whatever is passed to it as a scalar function
 #[derive(Debug, Default)]
 struct RecordingFunctionFactory {
diff --git a/datafusion/expr-common/src/signature.rs b/datafusion/expr-common/src/signature.rs
index 77ba1858e35b0..c9b3577ea7fae 100644
--- a/datafusion/expr-common/src/signature.rs
+++ b/datafusion/expr-common/src/signature.rs
@@ -343,6 +343,12 @@ impl TypeSignature {
     pub fn supports_zero_argument(&self) -> bool {
         match &self {
             TypeSignature::Exact(vec) => vec.is_empty(),
+            TypeSignature::Any(0) => true,
+            TypeSignature::Variadic(vec) => vec.is_empty(),
+            TypeSignature::VariadicAny => true,
+            TypeSignature::Uniform(0, _) => true,
+            TypeSignature::Coercible(vec) => vec.is_empty(),
+            TypeSignature::Comparable(0) => true,
             TypeSignature::Nullary => true,
             TypeSignature::OneOf(types) => types
                 .iter()