Can Scraper (Rust) be used in asynchronous Rust applications?

Yes, the scraper crate in Rust is designed for parsing HTML using CSS selectors, and it is not inherently asynchronous. However, you can use it within asynchronous Rust applications by combining it with asynchronous code that fetches the HTML content you want to parse.

In an asynchronous Rust application, you would typically use an async HTTP client like reqwest to fetch the web page's HTML content. Once you've obtained that content, you can then use the scraper crate to parse and extract the information you need.

Here's a simple example of how you could use scraper in an asynchronous Rust application:

use reqwest; // 0.11.4, tokio = { version = "1", features = ["full"] }
use scraper::{Html, Selector};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Use reqwest to perform an asynchronous HTTP GET request
    let res = reqwest::get("https://www.rust-lang.org")
        .await?
        .text()
        .await?;

    // Parse the HTML document with the `scraper` crate
    let document = Html::parse_document(&res);
    let selector = Selector::parse("a.headerLogo").unwrap();

    // Iterate over elements matching the selector
    for element in document.select(&selector) {
        // Do something with each element here, such as extracting text or an attribute
        if let Some(text) = element.text().next() {
            println!("Found text: {}", text);
        }
    }

    Ok(())
}

In this example, we're using tokio as the asynchronous runtime, and reqwest to make an HTTP GET request to the Rust website. Once the content is fetched, we use scraper to parse the HTML and extract the text of elements matching the CSS selector .headerLogo.

To run this example, you need to include the following dependencies in your Cargo.toml file:

[dependencies]
reqwest = { version = "0.11", features = ["json"] }
scraper = "0.12"
tokio = { version = "1", features = ["full"] }

Remember to adjust the versions as needed to match the latest or the versions compatible with your project.

This illustrates how scraper can be used within the context of asynchronous Rust code, even though scraper itself operates synchronously. The asynchronous part is the fetching of the content, while the parsing is done synchronously after the content has been fully retrieved.