How do I detect and handle page errors with headless_chrome (Rust)?

In Rust, when using the headless_chrome crate, handling page errors can be done by checking for the presence of error-related elements or messages on the page, or by catching error events triggered by the browser.

Let's go through an example of how you can handle page errors using the headless_chrome crate. Note that headless_chrome may not be actively maintained, so be sure to check for the latest tools or crates for working with headless Chrome in Rust.

Here's a step-by-step guide to detect and handle page errors:

1. Add the headless_chrome crate to your Cargo.toml:

   [dependencies]
   headless_chrome = "0.9.0" # Check for the latest version

1. Write Rust code to navigate to a page and check for errors: You need to create a Browser, navigate to a page, and then look for specific indicators of an error, such as the HTTP status code if it's available or specific error messages on the page.

   use headless_chrome::{Browser, LaunchOptionsBuilder};
   use std::sync::Arc;

   fn main() -> Result<(), failure::Error> {
       // Launch a new browser instance
       let browser = Browser::new(LaunchOptionsBuilder::default().build().unwrap())?;

       // Create a new tab and navigate to the desired URL
       let tab = browser.wait_for_initial_tab()?;
       tab.navigate_to("http://example.com")?;

       // Wait for network/javascript events to complete, if necessary
       tab.wait_until_navigated()?;

       // Example: Checking for a specific error element on the page
       match tab.find_element("css selector for error element") {
           Ok(element) => println!("Error element found: {:?}", element.get_description()?),
           Err(_) => println!("No error element found."),
       }

       // Optionally, you can also evaluate JavaScript to check for errors
       let result = tab.evaluate("window.someErrorCheckFunction()", true)?;
       if result.value.is_some() {
           println!("Error detected: {:?}", result.value.unwrap());
       }

       Ok(())
   }

1. Handle errors: After detecting an error, you may want to take specific actions such as retrying the request, logging the error, or gracefully exiting the application.

   // ...
   match tab.find_element("css selector for error element") {
       Ok(element) => {
           // Handle the error accordingly
           eprintln!("Error element found: {:?}", element.get_description()?);
           // For example, retrying the navigation
           // tab.navigate_to("http://example.com")?;
       },
       Err(_) => println!("No error element found."),
   }
   // ...

Keep in mind that the headless_chrome crate's API might have changed, and it's important to consult the latest documentation for the most accurate information.

Error handling in a headless browser context is generally more challenging than in a standard browser because you don't have the visual feedback of what's happening. You must rely on programmatic checks such as status codes, the presence of specific elements, or JavaScript execution results to understand what's going on in the browser.

If you find that headless_chrome does not meet your needs or is no longer maintained, consider using other libraries such as fantoccini or webdriver crate which provide similar functionality and may have better support for error handling. Remember to always check the documentation for the specific crate you decide to use.