Chrome extension content script re-injection after upgrade or install

Question

After the Chrome extension I'm working on is installed, or upgraded, the content scripts (specified in the manifest) are not re-injected so a page refresh is required to make the extension work. Is there a way to force the scripts to be injected again?

I believe I could inject them again programmatically by removing them from the manifest and then handling which pages to inject in the background page, but this is not a good solution.

I don't want to automatically refresh the user's tabs because that could lose some of their data. Safari automatically refreshes all pages when you install or upgrade an extension.

Answer 1

There's a way to allow a content script heavy extension to continue functioning after an upgrade, and to make it work immediately upon installation.

Install

The install method is to simply iterate through all tabs in all windows, and inject some scripts programmatically into tabs with matching URLs.

Obviously, you have to do it in a background page or event page script declared in manifest.json:

"background": {
    "scripts": ["background.js"]
},

background.js:

// Add a `manifest` property to the `chrome` object.
chrome.manifest = chrome.runtime.getManifest();

var injectIntoTab = function (tab) {
    // You could iterate through the content scripts here
    var scripts = chrome.manifest.content_scripts[0].js;
    var i = 0, s = scripts.length;
    for( ; i < s; i++ ) {
        chrome.tabs.executeScript(tab.id, {
            file: scripts[i]
        });
    }
}

// Get all windows
chrome.windows.getAll({
    populate: true
}, function (windows) {
    var i = 0, w = windows.length, currentWindow;
    for( ; i < w; i++ ) {
        currentWindow = windows[i];
        var j = 0, t = currentWindow.tabs.length, currentTab;
        for( ; j < t; j++ ) {
            currentTab = currentWindow.tabs[j];
            // Skip chrome:// and https:// pages
            if( ! currentTab.url.match(/(chrome|https):///gi) ) {
                injectIntoTab(currentTab);
            }
        }
    }
});

Upgrade

The upgrade method relies on the fact that the content scripts are left injected after an extension is disabled, uninstalled or upgraded.

When the port connection is made, an onDisconnect handler is added. This waits a second after the disconnect event, then attempts to reconnect. If it fails, another onDisconnect is fired so the process happens again, until a connection is made. It's not perfect, but it works.

The content script:

var port;

// Attempt to reconnect
var reconnectToExtension = function () {
    // Reset port
    port = null;
    // Attempt to reconnect after 1 second
    setTimeout(connectToExtension, 1000 * 1);
};

// Attempt to connect
var connectToExtension = function () {

    // Make the connection
    port = chrome.runtime.connect({name: "my-port"});
    
    // When extension is upgraded or disabled and renabled, the content scripts
    // will still be injected, so we have to reconnect them.
    // We listen for an onDisconnect event, and then wait for a second before
    // trying to connect again. Becuase chrome.runtime.connect fires an onDisconnect
    // event if it does not connect, an unsuccessful connection should trigger
    // another attempt, 1 second later.
    port.onDisconnect.addListener(reconnectToExtension);
  
};

// Connect for the first time
connectToExtension();