Building a sample Chrome extension, its sole purpose is to wrap/replace fetch and XMLHttpRequest.
It was easy with Manifest V2, but seems to be tricky with Manifest V3.
The replacement is achieved using chrome.scripting.executeScript, which is triggered immediately from a document_start content script, which sends a message to the background worker, which in turn uses chrome.scripting.executeScript on the calling tab.
The whole thing takes from 500ms to 1500ms, which usually misses many initial fetch/XMLHttpRequest requests, which is unacceptable for my use case - I need to control all requests.
Is it possible to delay scripts on the original tab until the replacement is finished? Am I doing something wrong here? Any other solution to guarantee a replacement before requests are made?
(using https://www.msnbc.com/ in this example, but tried many other websites)
manifest.json:
{
"name": "v3ChangeFetchExample",
"description": "v3ChangeFetchExample",
"version": "1.0",
"manifest_version": 3,
"background": {
"service_worker": "background.js"
},
"permissions": ["tabs", "scripting"],
"content_security_policy": {
"extension_pages": "script-src 'self'; object-src 'self'"
},
"content_scripts": [
{
"all_frames": true,
"js": ["script.js"],
"matches": ["https://www.msnbc.com/*"],
"run_at": "document_start"
}
],
"host_permissions": ["https://www.msnbc.com/*"]
}
background.js:
const replaceFetch = async function (message) {
fetch = {};
XMLHttpRequest = {};
console.error(`Took ${Date.now() - message}ms`);
};
chrome.runtime.onMessage.addListener(function (message, sender, sendResponse) {
chrome.scripting.executeScript({
world: "MAIN",
target: { tabId: sender.tab.id, allFrames: true },
func: replaceFetch,
args: [message],
});
sendResponse(true);
});
script.js:
(function () {
chrome.runtime.sendMessage(Date.now());
})();
Edit: Just found this in the documentation of chrome.scripting.executeScript:
Injects a script into a target context. The script will be run at document_idle.
This sheds some light on the issue. So maybe the question should be: Is it possible to execute a script on document_start, and not document_idle using Manifest V3?
