Is it possible to attach headless_chrome (Rust) to an existing browser session?

Attaching a headless Chrome browser instance, whether it's initiated from a Rust program or any other language binding, to an already running Chrome browser session is not a straightforward task. Google Chrome does not provide a built-in feature to attach a new headless Chrome instance to an existing session with cookies, tabs, and other session data.

However, you can start a headless Chrome session with specific parameters that allow for remote debugging. With remote debugging enabled, you can control the headless browser programmatically. This is typically done by launching Chrome with the --remote-debugging-port flag.

In Rust, you can use libraries such as headless_chrome to control a headless Chrome browser. To start a new Chrome browser session with remote debugging enabled, you can pass the appropriate flags to the Chrome binary. However, this will only allow you to control a new browser session, not attach to an existing one.

If you want to automate or control an existing Chrome session, you might consider using Chrome's DevTools Protocol (CDP) directly. The CDP allows for tools to instrument, inspect, debug, and profile Chromium, Chrome, and other Blink-based browsers. However, it requires that the existing browser session was started with remote debugging enabled.

Here's an example of how you could launch a Chrome browser with remote debugging using the command line:

chrome --remote-debugging-port=9222 --user-data-dir=/path/to/chrome-user-data

Then, in Rust, you could use a CDP client library to connect to the browser. For example, with the chrome-devtools-rs crate, you could write something like this:

use chrome_devtools as protocol;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Connect to the Chrome instance using the remote debugging port
    let (_session, mut connection) = protocol::tabs::connect("http://localhost:9222").await?;

    // Now you can send commands to the browser or inspect it using the CDP client
    // ...

    Ok(())
}

This code would allow you to control the Chrome instance with the specified remote debugging port. However, it would not allow you to attach to an existing Chrome session that was not started with remote debugging enabled.

In summary, if the browser session was not started with the intention of being remotely debuggable, you cannot simply attach a headless Chrome instance to it after the fact. If you need to automate or control an existing session, you need to ensure that it is started with the appropriate flags for remote debugging and then use a CDP client to interact with it.