From e785b99338ea364ed1b618cbc2b471ff065b15f3 Mon Sep 17 00:00:00 2001
From: Raymond Hill <rhill@raymondhill.net>
Date: Sat, 13 Jul 2024 11:02:54 -0400
Subject: [PATCH] Improve `prevent-fetch` scriptlet

Related discussion:
https://github.com/uBlockOrigin/uBlock-discussions/discussions/848#discussioncomment-10027757

Added support for AdGuard's `responseType` parameter. Extended the
meaning of that 3rd parameter to also be a JSON string with
properties to set on the returned response instance. Currently
supported properties:

- `ok`, supported values: `false`, `true`
- `type, supported values: `"basic"`, `"cors"`, `"opaque"`

Reference:
https://github.com/AdguardTeam/Scriptlets/blob/master/wiki/about-scriptlets.md#-%EF%B8%8F-prevent-fetch
---
 assets/resources/scriptlets.js | 51 +++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 22 deletions(-)

diff --git a/assets/resources/scriptlets.js b/assets/resources/scriptlets.js
index d3aedadc2..f753ba5a8 100644
--- a/assets/resources/scriptlets.js
+++ b/assets/resources/scriptlets.js
@@ -57,6 +57,7 @@ function safeSelf() {
         'Math_random': Math.random,
         'Object': Object,
         'Object_defineProperty': Object.defineProperty.bind(Object),
+        'Object_defineProperties': Object.defineProperties.bind(Object),
         'Object_fromEntries': Object.fromEntries.bind(Object),
         'Object_getOwnPropertyDescriptor': Object.getOwnPropertyDescriptor.bind(Object),
         'RegExp': self.RegExp,
@@ -2067,11 +2068,11 @@ builtinScriptlets.push({
 });
 function noFetchIf(
     propsToMatch = '',
-    responseBody = ''
+    responseBody = '',
+    responseType = ''
 ) {
-    if ( typeof propsToMatch !== 'string' ) { return; }
     const safe = safeSelf();
-    const logPrefix = safe.makeLogPrefix('prevent-fetch', propsToMatch, responseBody);
+    const logPrefix = safe.makeLogPrefix('prevent-fetch', propsToMatch, responseBody, responseType);
     const needles = [];
     for ( const condition of propsToMatch.split(/\s+/) ) {
         if ( condition === '' ) { continue; }
@@ -2086,6 +2087,26 @@ function noFetchIf(
         }
         needles.push({ key, re: safe.patternToRegex(value) });
     }
+    const validResponseProps = {
+        ok: [ false, true ],
+        type: [ 'basic', 'cors', 'opaque' ],
+    };
+    let responseProps;
+    if ( /^\{.*\}$/.test(responseType) ) {
+        responseProps = {};
+        try {
+            Object.entries(JSON.parse(responseType)).forEach(([ p, v ]) => {
+                if ( validResponseProps[p] === undefined ) { return; }
+                if ( validResponseProps[p].includes(v) === false ) { return; }
+                responseProps[p] = { value: v };
+            });
+        }
+        catch(ex) {}
+    } else if ( responseType !== '' ) {
+        if ( validResponseProps.type.includes(responseType) ) {
+            responseProps = { type: { value: responseType } };
+        }
+    }
     self.fetch = new Proxy(self.fetch, {
         apply: function(target, thisArg, args) {
             const details = args[0] instanceof self.Request
@@ -2123,17 +2144,6 @@ function noFetchIf(
             if ( proceed ) {
                 return Reflect.apply(target, thisArg, args);
             }
-            let responseType = '';
-            if ( details.mode === undefined || details.mode === 'cors' ) {
-                try {
-                    const desURL = new URL(details.url);
-                    responseType = desURL.origin !== document.location.origin
-                        ? 'cors'
-                        : 'basic';
-                } catch(ex) {
-                    safe.uboErr(logPrefix, `Error: ${ex}`);
-                }
-            }
             return generateContentFn(responseBody).then(text => {
                 safe.uboLog(logPrefix, `Prevented with response "${text}"`);
                 const response = new Response(text, {
@@ -2142,14 +2152,11 @@ function noFetchIf(
                         'Content-Length': text.length,
                     }
                 });
-                safe.Object_defineProperty(response, 'url', {
-                    value: details.url
-                });
-                if ( responseType !== '' ) {
-                    safe.Object_defineProperty(response, 'type', {
-                        value: responseType
-                    });
-                }
+                const props = Object.assign(
+                    { url: { value: details.url } },
+                    responseProps
+                );
+                safe.Object_defineProperties(response, props);
                 return response;
             });
         }