handle empty arrays and trailing commas

src/ast.rs

@@ -1,3 +1,4 @@
+use crate::error::UnexpectedTokenError;
 use crate::error::{ExpectToken, InvalidArrayKeyError, ParseError, ResultExt, SpannedError};
 use crate::lexer::Token;
 use crate::string::{unescape_double, unescape_single, UnescapeError};
@@ -124,7 +125,20 @@ fn parse_array<'source>(
     }
 
     loop {
-        let key_or_value = parse_lexer(source, lexer)?;
+        let key_or_value = match parse_lexer(source, lexer) {
+            Ok(value) => value,
+            Err(err) => {
+                // trailing comma or empty array
+                if matches!(
+                    err.error(),
+                    ParseError::UnexpectedToken(UnexpectedTokenError { found: None, .. })
+                ) {
+                    break;
+                } else {
+                    return Err(err);
+                }
+            }
+        };
         let key_or_value_span = lexer.span();
         let next = lexer
             .next()
@@ -202,6 +216,7 @@ fn test_parse() {
         Value::String("test".to_string()),
         parse(r#""test""#).unwrap()
     );
+    assert_eq!(Value::Array(hashmap! {}), parse(r#"array()"#).unwrap());
     assert_eq!(
         Value::Array(hashmap! {
             Key::Int(0) => Value::Int(3),
@@ -210,6 +225,14 @@ fn test_parse() {
         }),
         parse(r#"array(3,4,5)"#).unwrap()
     );
+    assert_eq!(
+        Value::Array(hashmap! {
+            Key::Int(0) => Value::Int(3),
+            Key::Int(1) => Value::Int(4),
+            Key::Int(2) => Value::Int(5),
+        }),
+        parse(r#"array(3,4,5,)"#).unwrap()
+    );
     assert_eq!(
         Value::Array(hashmap! {
             Key::Int(1) => Value::Int(3),

src/error.rs

@@ -27,6 +27,10 @@ impl<'a, T: Error + Debug> SpannedError<'a, T> {
             error,
         }
     }
+
+    pub fn error(&self) -> &T {
+        &self.error
+    }
 }
 
 const METRICS: DefaultMetrics = DefaultMetrics::with_tab_stop(4);

src/lexer.rs

@@ -1,5 +1,4 @@
 use logos::Logos;
-use std::fmt::{Display, Formatter};
 
 #[derive(Logos, Debug, PartialEq, Clone)]
 pub enum Token {
@@ -30,25 +29,6 @@ pub enum Token {
     Error,
 }
 
-impl Display for Token {
-    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Token::Array => write!(f, "array"),
-            Token::Bool => write!(f, "bool"),
-            Token::Arrow => write!(f, "arrow"),
-            Token::BracketOpen => write!(f, "bracket open"),
-            Token::BracketClose => write!(f, "bracket close"),
-            Token::SquareOpen => write!(f, "square bracket open"),
-            Token::SquareClose => write!(f, "square bracket close"),
-            Token::Comma => write!(f, "comma"),
-            Token::LiteralString => write!(f, "string literal"),
-            Token::Float => write!(f, "float literal"),
-            Token::Integer => write!(f, "integer literal"),
-            Token::Error => write!(f, "invalid token"),
-        }
-    }
-}
-
 #[test]
 fn test_lex() {
     let source = r###"