AG-27573 Fix set-constant - set proxy trap only once #380

Squashed commit of the following:

commit d325bd7
Merge: 95fded6 f5c5921
Author: Adam Wróblewski <adam@adguard.com>
Date:   Mon Nov 13 13:16:59 2023 +0100

    Merge branch 'master' into fix/AG-27573

commit 95fded6
Author: Slava Leleka <v.leleka@adguard.com>
Date:   Fri Nov 10 20:27:54 2023 +0300

    Update test

commit b30f892
Author: Slava Leleka <v.leleka@adguard.com>
Date:   Fri Nov 10 20:27:42 2023 +0300

    Update test

commit f76eaf3
Author: Adam Wróblewski <adam@adguard.com>
Date:   Fri Nov 10 17:57:42 2023 +0100

    Update test

commit f5543e8
Author: Adam Wróblewski <adam@adguard.com>
Date:   Fri Nov 10 15:58:22 2023 +0100

    Fix set-constant - set proxy trap only once

Author: AdamWr

CHANGELOG.md

@@ -19,6 +19,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- issue with setting proxy trap every time when property is accessed in `set-constant` scriptlet
+  [#380](https://github.com/AdguardTeam/Scriptlets/issues/380)
 - issue with `stack` in `evaldata-prune` scriptlet [#378](https://github.com/AdguardTeam/Scriptlets/issues/378)
 - issue with setting values to wrong properties in `set-constant` scriptlet
   [#373](https://github.com/AdguardTeam/Scriptlets/issues/373)

src/scriptlets/set-constant.js

@@ -155,6 +155,8 @@ export function setConstant(source, property, value, stack = '', valueWrapper =
         return;
     }
 
+    let isProxyTrapSet = false;
+
     const emptyArr = noopArray();
     const emptyObj = noopObject();
 
@@ -297,20 +299,23 @@ export function setConstant(source, property, value, stack = '', valueWrapper =
                     // Get properties which should be checked and remove first one
                     // because it's current object
                     const propertiesToCheck = property.split('.').slice(1);
-                    a = new Proxy(a, {
-                        get: (target, propertyKey, val) => {
-                            // Check if object contains required property, if so
-                            // check if current value is equal to constantValue, if not, set it to constantValue
-                            propertiesToCheck.reduce((object, currentProp, index, array) => {
-                                const currentObj = object?.[currentProp];
-                                if (currentObj && index === array.length - 1 && currentObj !== constantValue) {
-                                    object[currentProp] = constantValue;
-                                }
-                                return currentObj || object;
-                            }, target);
-                            return Reflect.get(target, propertyKey, val);
-                        },
-                    });
+                    if (!isProxyTrapSet) {
+                        isProxyTrapSet = true;
+                        a = new Proxy(a, {
+                            get: (target, propertyKey, val) => {
+                                // Check if object contains required property, if so
+                                // check if current value is equal to constantValue, if not, set it to constantValue
+                                propertiesToCheck.reduce((object, currentProp, index, array) => {
+                                    const currentObj = object?.[currentProp];
+                                    if (currentObj && index === array.length - 1 && currentObj !== constantValue) {
+                                        object[currentProp] = constantValue;
+                                    }
+                                    return currentObj || object;
+                                }, target);
+                                return Reflect.get(target, propertyKey, val);
+                            },
+                        });
+                    }
                 }
                 handler.set(a);
             },

tests/scriptlets/set-constant.test.js

@@ -795,4 +795,39 @@ if (!isSupported) {
         assert.strictEqual(window.something.start, undefined, 'something.start was not set');
         clearGlobalProps('something');
     });
+
+    test('Check if proxy was not set many times', (assert) => {
+        runScriptletFromTag('proxy.test.abc', 'trueFunc');
+
+        // Expected number of calls to getOwnPropertyDescriptor
+        const EXPECTED_NUMBER = 4;
+
+        let number = 0;
+        window.proxy = window.proxy || {};
+
+        const handler = {
+            getOwnPropertyDescriptor(target, prop) {
+                number += 1;
+                return Reflect.getOwnPropertyDescriptor(target, prop);
+            },
+        };
+
+        window.proxy = new Proxy(window.proxy, handler);
+
+        // Access object 100 times, if getOwnPropertyDescriptor was called more than 4 times
+        // it means that proxy was set more than once
+        for (let index = 0; index < 100; index += 1) {
+            if (number > EXPECTED_NUMBER) {
+                break;
+            }
+            window.proxy = window.proxy || {};
+        }
+        window.proxy.test = {
+            abc: () => false,
+        };
+        const result = window.proxy.test.abc();
+        assert.strictEqual(result, true, 'proxy.test.abc set to true by scriptlet');
+        assert.strictEqual(number, EXPECTED_NUMBER, `getOwnPropertyDescriptor was called ${EXPECTED_NUMBER} times`);
+        clearGlobalProps('proxy');
+    });
 }