Backport: feat: add default/elvis and coalescing operator. #64

Original commit:
jsonata-js/jsonata@9e1523d

Note: the fix of function boolean in functions.js was not required in Java (use of instanceof Map excludes functions already)

Author: uw4

src/main/java/com/dashjoin/jsonata/Parser.java

@@ -493,6 +493,26 @@ public Parser() {
         // merged Infix: register(new Prefix("-")); // unary numeric negation
         register(new Infix("~>")); // function application
 
+        // coalescing operator
+        register(new Infix("??", Tokenizer.operators.get("??")) {
+
+            @Override Symbol led(Symbol left) {
+                this.type = "condition";
+                Symbol c = new Symbol();
+                this.condition = c;
+                {
+                    c.type = "function";
+                    c.value = "(";
+                    Symbol p = new Symbol();
+                    c.procedure = p; p.type = "variable"; p.value = "exists";
+                    c.arguments = List.of(left);
+                }
+                this.then = left;
+                this._else = expression(0);
+                return this;
+            }
+        });
+
         register(new InfixR("(error)", 10) {
             @Override
             Symbol led(Symbol left) {
@@ -787,6 +807,18 @@ Symbol led(Symbol left) {
             }
         });
 
+        // elvis/default operator
+        register(new Infix("?:", Tokenizer.operators.get("?:")) {
+
+            @Override Symbol led(Symbol left) {
+                this.type = "condition";
+                this.condition = left;
+                this.then = left;
+                this._else = expression(0);
+                return this;
+            }
+        });
+
         // object transformer
         register(new Prefix("|") {
 

src/main/java/com/dashjoin/jsonata/Tokenizer.java

@@ -61,6 +61,8 @@ public class Tokenizer { // = function (path) {
     put("<=", 40);
     put(">=", 40);
     put("~>", 40);
+    put("?:", 40);
+    put("??", 40);
     put("and", 30);
     put("or", 25);
     put("in", 40);
@@ -232,6 +234,16 @@ Token next(boolean prefix) {
             position += 2;
             return create("operator", "~>");
         }
+        if (currentChar == '?' && haveMore && path.charAt(position + 1) == ':') {
+            // ?: default / elvis operator
+            position += 2;
+            return create("operator", "?:");
+        }
+        if (currentChar == '?' && haveMore && path.charAt(position + 1) == '?') {
+            // ?? coalescing operator
+            position += 2;
+            return create("operator", "??");
+        }
         // test for single char operators
         if (operators.get(""+currentChar)!=null) {
             position++;