Support named arguments in function invocations (apache#250)

This commit supports functions with argument names.

the format is :
"Select some_function( a => exp, b => exp2 .. ) FROM table1
OR
"select * from table(function(a => exp)) f;"

see:
https://jakewheat.github.io/sql-overview/sql-2016-foundation-grammar.html#named-argument-assignment-token
or the motivating example from snowflake:
https://docs.snowflake.com/en/sql-reference/functions/flatten.html

Author: eyalleshem

src/ast/mod.rs

@@ -873,12 +873,28 @@ impl fmt::Display for Assignment {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum FunctionArg {
+    Named { name: Ident, arg: Expr },
+    Unnamed(Expr),
+}
+
+impl fmt::Display for FunctionArg {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            FunctionArg::Named { name, arg } => write!(f, "{} => {}", name, arg),
+            FunctionArg::Unnamed(unnamed_arg) => write!(f, "{}", unnamed_arg),
+        }
+    }
+}
+
 /// A function call
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct Function {
     pub name: ObjectName,
-    pub args: Vec<Expr>,
+    pub args: Vec<FunctionArg>,
     pub over: Option<WindowSpec>,
     // aggregate functions may specify eg `COUNT(DISTINCT x)`
     pub distinct: bool,

src/ast/query.rs

@@ -226,7 +226,7 @@ pub enum TableFactor {
         /// Arguments of a table-valued function, as supported by Postgres
         /// and MSSQL. Note that deprecated MSSQL `FROM foo (NOLOCK)` syntax
         /// will also be parsed as `args`.
-        args: Vec<Expr>,
+        args: Vec<FunctionArg>,
         /// MSSQL-specific `WITH (...)` hints such as NOLOCK.
         with_hints: Vec<Expr>,
     },

src/parser.rs

@@ -2203,11 +2203,24 @@ impl Parser {
         Ok(Assignment { id, value })
     }
 
-    pub fn parse_optional_args(&mut self) -> Result<Vec<Expr>, ParserError> {
+    fn parse_function_args(&mut self) -> Result<FunctionArg, ParserError> {
+        if self.peek_nth_token(1) == Token::RArrow {
+            let name = self.parse_identifier()?;
+
+            self.expect_token(&Token::RArrow)?;
+            let arg = self.parse_expr()?;
+
+            Ok(FunctionArg::Named { name, arg })
+        } else {
+            Ok(FunctionArg::Unnamed(self.parse_expr()?))
+        }
+    }
+
+    pub fn parse_optional_args(&mut self) -> Result<Vec<FunctionArg>, ParserError> {
         if self.consume_token(&Token::RParen) {
             Ok(vec![])
         } else {
-            let args = self.parse_comma_separated(Parser::parse_expr)?;
+            let args = self.parse_comma_separated(Parser::parse_function_args)?;
             self.expect_token(&Token::RParen)?;
             Ok(args)
         }

src/tokenizer.rs

@@ -99,6 +99,8 @@ pub enum Token {
     LBrace,
     /// Right brace `}`
     RBrace,
+    /// Right Arrow `=>`
+    RArrow,
 }
 
 impl fmt::Display for Token {
@@ -139,6 +141,7 @@ impl fmt::Display for Token {
             Token::Pipe => f.write_str("|"),
             Token::LBrace => f.write_str("{"),
             Token::RBrace => f.write_str("}"),
+            Token::RArrow => f.write_str("=>"),
         }
     }
 }
@@ -400,7 +403,13 @@ impl<'a> Tokenizer<'a> {
                         _ => Ok(Some(Token::Pipe)),
                     }
                 }
-                '=' => self.consume_and_return(chars, Token::Eq),
+                '=' => {
+                    chars.next(); // consume
+                    match chars.peek() {
+                        Some('>') => self.consume_and_return(chars, Token::RArrow),
+                        _ => Ok(Some(Token::Eq)),
+                    }
+                }
                 '.' => self.consume_and_return(chars, Token::Period),
                 '!' => {
                     chars.next(); // consume
@@ -766,6 +775,23 @@ mod tests {
         compare(expected, tokens);
     }
 
+    #[test]
+    fn tokenize_right_arrow() {
+        let sql = String::from("FUNCTION(key=>value)");
+        let dialect = GenericDialect {};
+        let mut tokenizer = Tokenizer::new(&dialect, &sql);
+        let tokens = tokenizer.tokenize().unwrap();
+        let expected = vec![
+            Token::make_word("FUNCTION", None),
+            Token::LParen,
+            Token::make_word("key", None),
+            Token::RArrow,
+            Token::make_word("value", None),
+            Token::RParen,
+        ];
+        compare(expected, tokens);
+    }
+
     #[test]
     fn tokenize_is_null() {
         let sql = String::from("a IS NULL");

tests/sqlparser_common.rs

@@ -325,7 +325,7 @@ fn parse_select_count_wildcard() {
     assert_eq!(
         &Expr::Function(Function {
             name: ObjectName(vec![Ident::new("COUNT")]),
-            args: vec![Expr::Wildcard],
+            args: vec![FunctionArg::Unnamed(Expr::Wildcard)],
             over: None,
             distinct: false,
         }),
@@ -340,10 +340,10 @@ fn parse_select_count_distinct() {
     assert_eq!(
         &Expr::Function(Function {
             name: ObjectName(vec![Ident::new("COUNT")]),
-            args: vec![Expr::UnaryOp {
+            args: vec![FunctionArg::Unnamed(Expr::UnaryOp {
                 op: UnaryOperator::Plus,
                 expr: Box::new(Expr::Identifier(Ident::new("x")))
-            }],
+            })],
             over: None,
             distinct: true,
         }),
@@ -883,7 +883,7 @@ fn parse_select_having() {
         Some(Expr::BinaryOp {
             left: Box::new(Expr::Function(Function {
                 name: ObjectName(vec![Ident::new("COUNT")]),
-                args: vec![Expr::Wildcard],
+                args: vec![FunctionArg::Unnamed(Expr::Wildcard)],
                 over: None,
                 distinct: false
             })),
@@ -1589,7 +1589,32 @@ fn parse_scalar_function_in_projection() {
     assert_eq!(
         &Expr::Function(Function {
             name: ObjectName(vec![Ident::new("sqrt")]),
-            args: vec![Expr::Identifier(Ident::new("id"))],
+            args: vec![FunctionArg::Unnamed(Expr::Identifier(Ident::new("id")))],
+            over: None,
+            distinct: false,
+        }),
+        expr_from_projection(only(&select.projection))
+    );
+}
+
+#[test]
+fn parse_named_argument_function() {
+    let sql = "SELECT FUN(a => '1', b => '2') FROM foo";
+    let select = verified_only_select(sql);
+
+    assert_eq!(
+        &Expr::Function(Function {
+            name: ObjectName(vec![Ident::new("FUN")]),
+            args: vec![
+                FunctionArg::Named {
+                    name: Ident::new("a"),
+                    arg: Expr::Value(Value::SingleQuotedString("1".to_owned()))
+                },
+                FunctionArg::Named {
+                    name: Ident::new("b"),
+                    arg: Expr::Value(Value::SingleQuotedString("2".to_owned()))
+                },
+            ],
             over: None,
             distinct: false,
         }),