MapExpression improvements.

Author: afoucret

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/Literal.java

@@ -193,6 +193,10 @@ public static Literal keyword(Source source, String literal) {
         return new Literal(source, BytesRefs.toBytesRef(literal), KEYWORD);
     }
 
+    public static Literal keyword(Source source, Collection<String> literal) {
+        return new Literal(source, literal.stream().map(BytesRefs::toBytesRef).toList(), KEYWORD);
+    }
+
     /**
      * Not all literal values are currently supported in StreamInput/StreamOutput as generic values.
      * This mapper allows for addition of new and interesting values without (yet) adding to StreamInput/Output.

x-pack/plugin/esql/src/main/antlr/parser/Expression.g4

@@ -49,14 +49,15 @@ primaryExpression
 
 functionExpression
     : functionName LP (ASTERISK | (booleanExpression (COMMA booleanExpression)* (COMMA mapExpression)?))? RP
+    | functionName LP mapExpression? RP
     ;
 
 functionName
     : identifierOrParameter
     ;
 
 mapExpression
-    : LEFT_BRACES entryExpression (COMMA entryExpression)* RIGHT_BRACES
+    : LEFT_BRACES (entryExpression (COMMA entryExpression)*)? RIGHT_BRACES
     ;
 
 entryExpression