Add null

Author: Gijsreyn

docs/reference/schemas/config/functions/last.md

@@ -23,8 +23,7 @@ item in a sequence, the final stage in a deployment pipeline, or the last
 character in a configuration value.
 
 For arrays, it returns the element at index `length - 1`. For strings, it
-returns the last character as a string. If the input is empty, an error is
-returned.
+returns the last character as a string.
 
 ## Examples
 
@@ -207,16 +206,17 @@ Returns the last element of the array (preserving its original type) or the
 last character as a string. For arrays, the return type matches the element
 type. For strings, returns a single-character string.
 
+If the input is an empty array, the function returns `null`. If the input is an
+empty string, the function returns an empty string.
+
 ```yaml
-Type: any | string
+Type: any | string | null
 ```
 
 ## Errors
 
 The function returns an error in the following cases:
 
-- **Empty array**: The input array has no elements
-- **Empty string**: The input string has no characters
 - **Invalid type**: The argument is not an array or string
 
 ## Related functions

dsc/tests/dsc_functions.tests.ps1

@@ -510,6 +510,8 @@ Describe 'tests for function expressions' {
     @{ expression = "[last('hello')]"; expected = 'o' }
     @{ expression = "[last('a')]"; expected = 'a' }
     @{ expression = "[last(array('mixed'))]"; expected = 'mixed' }
+    @{ expression = "[last(createArray())]"; expected = $null }
+    @{ expression = "[last('')]"; expected = '' }
   ) {
     param($expression, $expected)
 

lib/dsc-lib/locales/en-us.toml

@@ -346,8 +346,6 @@ invalidArgType = "Invalid argument type, argument must be an array or string"
 [functions.last]
 description = "Returns the last element of an array or last character of a string"
 invoked = "last function"
-emptyArray = "Cannot get last element of empty array"
-emptyString = "Cannot get last character of empty string"
 invalidArgType = "Invalid argument type, argument must be an array or string"
 
 [functions.greater]

lib/dsc-lib/src/functions/last.rs

@@ -21,7 +21,7 @@ impl Function for Last {
             max_args: 1,
             accepted_arg_ordered_types: vec![vec![FunctionArgKind::Array, FunctionArgKind::String]],
             remaining_arg_accepted_types: None,
-            return_types: vec![FunctionArgKind::String, FunctionArgKind::Number, FunctionArgKind::Array, FunctionArgKind::Object],
+            return_types: vec![FunctionArgKind::String, FunctionArgKind::Number, FunctionArgKind::Array, FunctionArgKind::Object, FunctionArgKind::Null],
         }
     }
 
@@ -30,14 +30,14 @@ impl Function for Last {
 
         if let Some(array) = args[0].as_array() {
             if array.is_empty() {
-                return Err(DscError::Parser(t!("functions.last.emptyArray").to_string()));
+                return Ok(Value::Null);
             }
             return Ok(array[array.len() - 1].clone());
         }
 
         if let Some(string) = args[0].as_str() {
             if string.is_empty() {
-                return Err(DscError::Parser(t!("functions.last.emptyString").to_string()));
+                return Ok(Value::String(String::new()));
             }
             return Ok(Value::String(string.chars().last().unwrap().to_string()));
         }
@@ -86,20 +86,6 @@ mod tests {
         assert_eq!(result.as_str(), Some("a"));
     }
 
-    #[test]
-    fn empty_array() {
-        let mut parser = Statement::new().unwrap();
-        let result = parser.parse_and_execute("[last(createArray())]", &Context::new());
-        assert!(result.is_err());
-    }
-
-    #[test]
-    fn empty_string() {
-        let mut parser = Statement::new().unwrap();
-        let result = parser.parse_and_execute("[last('')]", &Context::new());
-        assert!(result.is_err());
-    }
-
     #[test]
     fn invalid_type_object() {
         let mut parser = Statement::new().unwrap();