Fix filter query existence tests in logical expressions.

src/path/expression.ts

@@ -118,22 +118,25 @@ export class PrefixExpression extends FilterExpression {
 }
 
 export class InfixExpression extends FilterExpression {
+  readonly logical: boolean;
+
   constructor(
     readonly token: Token,
     readonly left: FilterExpression,
     readonly operator: string,
     readonly right: FilterExpression,
   ) {
     super(token);
+    this.logical = operator === "&&" || operator === "||";
   }
 
   public evaluate(context: FilterContext): boolean {
     let left = this.left.evaluate(context);
-    if (left instanceof JSONPathNodeList && left.nodes.length === 1)
+    if (!this.logical && left instanceof JSONPathNodeList && left.nodes.length === 1)
       left = left.nodes[0].value;
 
     let right = this.right.evaluate(context);
-    if (right instanceof JSONPathNodeList && right.nodes.length === 1)
+    if (!this.logical && right instanceof JSONPathNodeList && right.nodes.length === 1)
       right = right.nodes[0].value;
 
     if (this.operator === "&&") {
@@ -148,7 +151,7 @@ export class InfixExpression extends FilterExpression {
   }
 
   public toString(): string {
-    if (this.operator === "&&" || this.operator === "||") {
+    if (this.logical) {
       return `(${this.left.toString()} ${
         this.operator
       } ${this.right.toString()})`;

tests/path/query.test.ts

@@ -0,0 +1,10 @@
+import { query } from "../../src/path";
+
+describe("JSONPath query", () => {
+    test("logical expression, existence tests", () => {
+      const path = "$[[email protected] && @.b]";
+      const data =  [{"a": false, "b": false}];
+      expect(query(path, data).values()).toStrictEqual([{"a": false, "b": false}]);
+    });
+  }
+);