ethers-rs/ethers-core/src/utils/ganache.rs

use std::{
    process::{Child, Command},
    time::Duration,
};

const SLEEP_TIME: Duration = Duration::from_secs(3);

/// A ganache CLI instance. Will close the instance when dropped.
///
/// Construct this using [`Ganache`](./struct.Ganache.html)
pub struct GanacheInstance(Child);

impl Drop for GanacheInstance {
    fn drop(&mut self) {
        self.0.kill().expect("could not kill ganache");
    }
}

/// Builder for launching `ganache-cli`.
///
/// # Panics
///
/// If `spawn` is called without `ganache-cli` being available in the user's $PATH
///
/// # Example
///
/// ```no_run
/// use ethers::utils::Ganache;
///
/// let port = 8545u64;
/// let url = format!("http://localhost:{}", port).to_string();
///
/// let ganache = Ganache::new()
///     .port(port)
///     .mnemonic("abstract vacuum mammal awkward pudding scene penalty purchase dinner depart evoke puzzle")
///     .spawn();
///
/// drop(ganache); // this will kill the instance
/// ```
#[derive(Clone, Default)]
pub struct Ganache {
    port: Option<u64>,
    block_time: Option<u64>,
    mnemonic: Option<String>,
}

impl Ganache {
    /// Creates an empty Ganache builder.
    /// The default port is 8545. The mnemonic is chosen randomly.
    pub fn new() -> Self {
        Self::default()
    }

    /// Sets the port which will be used when the `ganache-cli` instance is launched.
    pub fn port<T: Into<u64>>(mut self, port: T) -> Self {
        self.port = Some(port.into());
        self
    }

    /// Sets the mnemonic which will be used when the `ganache-cli` instance is launched.
    pub fn mnemonic<T: Into<String>>(mut self, mnemonic: T) -> Self {
        self.mnemonic = Some(mnemonic.into());
        self
    }

    /// Sets the block-time which will be used when the `ganache-cli` instance is launched.
    pub fn block_time<T: Into<u64>>(mut self, block_time: T) -> Self {
        self.block_time = Some(block_time.into());
        self
    }

    /// Consumes the builder and spawns `ganache-cli` with stdout redirected
    /// to /dev/null. This takes ~2 seconds to execute as it blocks while
    /// waiting for `ganache-cli` to launch.
    pub fn spawn(self) -> GanacheInstance {
        let mut cmd = Command::new("ganache-cli");
        cmd.stdout(std::process::Stdio::null());
        if let Some(port) = self.port {
            cmd.arg("-p").arg(port.to_string());
        }

        if let Some(mnemonic) = self.mnemonic {
            cmd.arg("-m").arg(mnemonic);
        }

        if let Some(block_time) = self.block_time {
            cmd.arg("-b").arg(block_time.to_string());
        }

        let ganache_pid = cmd.spawn().expect("couldnt start ganache-cli");

        // wait a couple of seconds for ganache to boot up
        std::thread::sleep(SLEEP_TIME);
        GanacheInstance(ganache_pid)
    }
}