Multiple outputs

Reporting tests result to multiple outputs simultaneously may be achieved by using writer::Tee.

extern crate cucumber;
extern crate tokio;

use std::{fs, io};
use cucumber::{writer, World as _, WriterExt as _};

#[derive(cucumber::World, Debug, Default)]
struct World;

#[tokio::main]
async fn main() -> io::Result<()> {
let file = fs::File::create(format!("{}/report.xml", env!("OUT_DIR")))?;
World::cucumber()
    .with_writer(
        // NOTE: `Writer`s pipeline is constructed in a reversed order.
        writer::Basic::stdout() // And output to STDOUT.
            .summarized()       // Simultaneously, add execution summary.
            .tee::<World, _>(writer::JUnit::for_tee(file, 0)) // Then, output to XML file.
            .normalized()       // First, normalize events order.
    )
    .run_and_exit("tests/features/book")
    .await;
Ok(())
}

Using the same Writer multiple times

While using writer::Tee for different Writers is OK and straightforward most of the time, reusing the same Writer multiple times isn't so obvious, because of the clap complaining about identical CLI options (unfortunately, in a form of runtime panic only).

extern crate cucumber;
extern crate tokio;

use std::{fs, io};
use cucumber::{writer, World as _, WriterExt as _};

#[derive(cucumber::World, Debug, Default)]
struct World;

#[tokio::main]
async fn main() -> io::Result<()> {
let file = fs::File::create(format!("{}/report.txt", env!("OUT_DIR")))?;
World::cucumber()
    .with_writer(
        writer::Basic::raw(
            io::stdout(),
            writer::Coloring::Auto,
            writer::Verbosity::Default,
        )
            .tee::<World, _>(writer::Basic::raw(
                file,
                writer::Coloring::Never,
                2,
            ))
            .summarized()
            .normalized(),
    )
    .run_and_exit("tests/features/book")
    .await;
Ok(())
}

thread 'main' panicked at 'Command cucumber: Argument names must be unique, but 'verbose' is in use by more than one argument or group'

To avoid this, you should manually construct the desired cli::Opts and supply them via Cucumber::with_cli() method. Example below uses two different writer::Basics, where one outputs to STDOUT and another one outputs to a file:

extern crate cucumber;
extern crate tokio;

use std::{fs, io};
use cucumber::{cli, writer, World as _, WriterExt as _};

#[derive(cucumber::World, Debug, Default)]
struct World;

#[tokio::main]
async fn main() -> io::Result<()> {
// Parse CLI arguments for a single `writer::Basic`.
let cli = cli::Opts::<_, _, writer::basic::Cli>::parsed();
let cli = cli::Opts {
    re_filter: cli.re_filter,
    tags_filter: cli.tags_filter,
    parser: cli.parser,
    runner: cli.runner,
    // Replicate CLI arguments for every `writer::Basic`. 
    writer: cli::Compose {
        left: cli.writer.clone(),
        right: cli.writer,
    },
    custom: cli.custom,
};

let file = fs::File::create(format!("{}/report.txt", env!("OUT_DIR")))?;
World::cucumber()
    .with_writer(
        writer::Basic::raw(
            io::stdout(),
            writer::Coloring::Auto,
            writer::Verbosity::Default,
        )
        .tee::<World, _>(writer::Basic::raw(
            file,
            writer::Coloring::Never,
            2,
        ))
        .summarized()
        .normalized(),
    )
    .with_cli(cli) // Supply the parsed `cli::Opts`.
    .run_and_exit("tests/features/book")
    .await;
Ok(())
}