ch_rds/dev/

mod.rs

use std::collections::{BTreeSet, HashMap, VecDeque};
use std::env;
use std::ffi::{OsStr, OsString};
use std::fs;
use std::io::{Read, Write};
use std::net::{SocketAddr, TcpStream};
use std::path::{Path, PathBuf};
use std::process::{self, Command as ProcessCommand};
use std::thread;
use std::time::{Duration, Instant, SystemTime};

#[cfg(feature = "btcpay")]
mod btcpay;

#[cfg(feature = "btcpay")]
pub use self::btcpay::BtcpayDevProfile;
#[cfg(feature = "btcpay")]
use self::btcpay::{LocalBtcpayBootstrapOptions, bootstrap_local_btcpay};
use clap::{Args, Parser, Subcommand};
use color_eyre::eyre::{Context, bail, ensure};
use serde::Deserialize;
use serde_json::Value;

/// Result type returned by development workflow operations.
pub type DevResult<T = ()> = color_eyre::Result<T>;

#[derive(Parser, Debug)]
#[command(about = "Build and run the current application's backend and web frontend.")]
struct AppCli {
    #[command(subcommand)]
    command: AppCommand,
}

#[derive(Subcommand, Debug)]
enum AppCommand {
    /// Run the backend and web development server with automatic reloads.
    Watch(AppWatchCommand),
    /// Build the web assets, then run the backend.
    Serve(AppRunCommand),
    /// Build the web assets without starting the backend.
    Build(AppBuildCommand),
    /// Rebuild one generated browser asset from the active project profile.
    #[command(hide = true)]
    BuildPublicAsset(AppPublicAssetBuildCommand),
}

#[derive(Args, Debug)]
struct AppRunCommand {
    #[command(flatten)]
    optional_assets: OptionalAssetsArgs,
    #[arg(long)]
    release: bool,
    #[arg(short, long, action = clap::ArgAction::Count)]
    verbose: u8,
}

#[derive(Args, Debug, Default)]
struct OptionalAssetsArgs {
    /// Include assets registered as optional by the project profile.
    #[arg(long = "with-optional-assets", alias = "editor")]
    include_optional_assets: bool,
}

#[derive(Args, Debug)]
struct AppWatchCommand {
    #[command(flatten)]
    run: AppRunCommand,
    /// Start the backend once instead of rebuilding it for every watched Rust change.
    #[arg(long)]
    no_backend_reload: bool,
}

#[derive(Args, Debug)]
struct AppBuildCommand {
    #[command(flatten)]
    optional_assets: OptionalAssetsArgs,
    #[arg(short, long, action = clap::ArgAction::Count)]
    verbose: u8,
}

#[derive(Args, Debug)]
struct AppPublicAssetBuildCommand {
    #[arg(long)]
    id: String,
    #[arg(long)]
    release: bool,
    /// Override this asset's Cargo output directory with an absolute path.
    #[arg(long)]
    target_dir: Option<PathBuf>,
}

#[derive(Clone, Debug)]
/// Describes the backend, web client, and generated assets of one project.
pub struct ProjectProfile {
    app_id: String,
    web_dir: String,
    bin_target: Option<String>,
    api_addr: String,
    backend_ready_timeout: Duration,
    backend_ready_path: Option<String>,
    backend_target_dir: Option<String>,
    web_backend_origin_env: Option<String>,
    #[cfg(feature = "btcpay")]
    btcpay: Option<BtcpayDevProfile>,
    public_assets: Vec<ProjectPublicAsset>,
    optional_public_assets: Vec<ProjectPublicAsset>,
}

#[derive(Clone, Debug, Deserialize)]
#[serde(tag = "kind", rename_all = "kebab-case")]
/// A browser asset that must be built before the web client is served.
pub enum ProjectPublicAsset {
    /// A Rust package compiled to WebAssembly and processed by `wasm-bindgen`.
    WasmBindgen(WasmBindgenPublicAsset),
}

#[derive(Clone, Debug, Deserialize)]
/// Build settings for a public WebAssembly asset produced by `wasm-bindgen`.
pub struct WasmBindgenPublicAsset {
    id: String,
    label: String,
    package: String,
    wasm_file: String,
    #[serde(default)]
    no_default_features: bool,
    #[serde(default)]
    features: String,
    #[serde(default)]
    target_dir: Option<String>,
    out_dir: Vec<String>,
    out_name: String,
    wasm_bindgen_version: String,
}

#[derive(Clone, Copy, Debug)]
/// Selects how the backend and web client are run after preparation.
pub enum RunMode {
    /// Run both processes in development mode and rebuild on source changes.
    Watch,
    /// Build the web client once, then serve it from the backend.
    Serve,
}

#[derive(Debug)]
/// Resolved workspace, project, and web-client directories for a project.
pub struct WorkspacePaths {
    workspace_root: PathBuf,
    project_root: PathBuf,
    web_root: PathBuf,
}

#[derive(Debug, Deserialize)]
struct CargoMetadata {
    packages: Vec<CargoPackage>,
    resolve: Option<CargoResolve>,
}

#[derive(Debug, Deserialize)]
struct CargoPackage {
    id: String,
    name: String,
    source: Option<String>,
    manifest_path: PathBuf,
    targets: Vec<CargoTarget>,
}

#[derive(Debug, Deserialize)]
struct CargoTarget {
    kind: Vec<String>,
    name: String,
    src_path: PathBuf,
}

#[derive(Debug, Deserialize)]
struct CargoResolve {
    nodes: Vec<CargoResolveNode>,
}

#[derive(Debug, Deserialize)]
struct CargoResolveNode {
    id: String,
    deps: Vec<CargoResolveDependency>,
}

#[derive(Debug, Deserialize)]
struct CargoResolveDependency {
    pkg: String,
}

#[derive(Debug, Default, Eq, PartialEq)]
struct BackendWatchPaths {
    paths: Vec<PathBuf>,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
struct BackendArtifactStamp {
    modified: SystemTime,
    length: u64,
}

/// Owns a child process so every return path terminates and reaps it.
#[derive(Debug)]
struct ManagedChild {
    child: process::Child,
}

impl std::ops::Deref for ManagedChild {
    type Target = process::Child;
    fn deref(&self) -> &Self::Target {
        &self.child
    }
}

impl std::ops::DerefMut for ManagedChild {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.child
    }
}

impl ManagedChild {
    fn terminate(&mut self) {
        let _ = self.child.kill();
        let _ = self.child.wait();
    }
}

impl Drop for ManagedChild {
    fn drop(&mut self) {
        self.terminate();
    }
}

#[derive(Debug)]
struct BackendWatchRuntime {
    process: ManagedChild,
    builder: Option<ManagedChild>,
    artifact: Option<PathBuf>,
    active_image: Option<PathBuf>,
    active_stamp: Option<BackendArtifactStamp>,
    generation: u64,
}

const DEFAULT_BACKEND_READY_TIMEOUT: Duration = Duration::from_secs(300);
const BACKEND_READY_POLL_INTERVAL: Duration = Duration::from_millis(250);
const BACKEND_READY_CONNECT_TIMEOUT: Duration = Duration::from_millis(200);
const WATCH_DEBOUNCE: &str = "750ms";

impl ProjectProfile {
    /// Creates a project profile from its explicit project id and backend bind address.
    ///
    /// The backend binary target defaults to the same project id. Callers can
    /// override it when the Cargo binary intentionally uses a different name.
    pub fn new(app_id: impl Into<String>, api_addr: impl Into<String>) -> Self {
        Self {
            app_id: app_id.into(),
            web_dir: "web".to_string(),
            bin_target: None,
            api_addr: api_addr.into(),
            backend_ready_timeout: DEFAULT_BACKEND_READY_TIMEOUT,
            backend_ready_path: None,
            backend_target_dir: None,
            web_backend_origin_env: None,
            #[cfg(feature = "btcpay")]
            btcpay: None,
            public_assets: Vec::new(),
            optional_public_assets: Vec::new(),
        }
    }

    /// Overrides the web-client directory relative to the project root.
    pub fn with_web_dir(mut self, web_dir: impl Into<String>) -> Self {
        self.web_dir = web_dir.into();
        self
    }

    /// Overrides the backend binary when it does not follow the app repository prefix.
    pub fn with_bin_target(mut self, bin_target: impl Into<String>) -> Self {
        self.bin_target = Some(bin_target.into());
        self
    }

    /// Overrides how long `watch` waits for a cold backend build to open its listener.
    pub fn with_backend_ready_timeout(mut self, timeout: Duration) -> Self {
        self.backend_ready_timeout = timeout;
        self
    }

    /// Waits for an HTTP response from this path before activating a backend build.
    pub fn with_backend_ready_path(mut self, path: impl Into<String>) -> Self {
        self.backend_ready_path = Some(path.into());
        self
    }

    /// Isolates backend builds from other Cargo processes in the same workspace.
    pub fn with_backend_target_dir(mut self, target_dir: impl Into<String>) -> Self {
        self.backend_target_dir = Some(target_dir.into());
        self
    }

    /// Sets the environment variable used to expose the backend origin to the web client.
    pub fn with_web_backend_origin_env(mut self, key: impl Into<String>) -> Self {
        self.web_backend_origin_env = Some(key.into());
        self
    }

    #[cfg(feature = "btcpay")]
    /// Attaches typed settings for the optional local BTCPay development stack.
    pub fn with_btcpay_profile(mut self, profile: BtcpayDevProfile) -> Self {
        self.btcpay = Some(profile);
        self
    }

    /// Registers an additional browser asset to build before the web client.
    pub fn with_public_asset(mut self, asset: ProjectPublicAsset) -> Self {
        self.public_assets.push(asset);
        self
    }

    /// Registers a browser asset that is built only when optional assets are requested.
    pub fn with_optional_public_asset(mut self, asset: ProjectPublicAsset) -> Self {
        self.optional_public_assets.push(asset);
        self
    }

    /// Returns the explicit project identifier.
    pub fn app_id(&self) -> &str {
        &self.app_id
    }

    /// Returns the configured backend binary target or the project identifier.
    pub fn bin_target(&self) -> &str {
        self.bin_target.as_deref().unwrap_or(&self.app_id)
    }

    /// Validates the profile and annotates failures with the supplied source label.
    pub fn validate(&self, source: &str) -> DevResult {
        ensure!(
            !self.app_id.trim().is_empty(),
            "{source} contains an empty app id"
        );
        ensure!(
            !self.web_dir.trim().is_empty(),
            "{source} project `{}` has an empty web_dir",
            self.app_id
        );
        ensure!(
            !self.bin_target().trim().is_empty(),
            "{source} project `{}` has an empty bin_target",
            self.app_id
        );
        ensure!(
            !self.backend_ready_timeout.is_zero(),
            "{source} project `{}` has a zero backend readiness timeout",
            self.app_id
        );
        if let Some(path) = &self.backend_ready_path {
            ensure!(
                path.starts_with('/') && !path.chars().any(char::is_control),
                "{source} project `{}` has an invalid backend readiness path",
                self.app_id
            );
        }
        if let Some(target_dir) = &self.backend_target_dir {
            ensure!(
                !target_dir.trim().is_empty(),
                "{source} project `{}` has an empty backend target directory",
                self.app_id
            );
        }
        api_addr(self)?;

        for asset in &self.public_assets {
            asset.validate(source, &self.app_id)?;
        }
        for asset in &self.optional_public_assets {
            asset.validate(source, &self.app_id)?;
        }
        #[cfg(feature = "btcpay")]
        {
            if let Some(profile) = &self.btcpay {
                profile.validate().map_err(|error| {
                    color_eyre::eyre::eyre!(
                        "{source} project `{}` has an invalid BTCPay profile: {error:#}",
                        self.app_id
                    )
                })?;
            }
        }

        Ok(())
    }
}

impl ProjectPublicAsset {
    /// Creates a `wasm-bindgen` asset build from explicit package and output settings.
    pub fn wasm_bindgen(
        id: impl Into<String>,
        label: impl Into<String>,
        package: impl Into<String>,
        wasm_file: impl Into<String>,
        out_dir: impl Into<Vec<String>>,
        out_name: impl Into<String>,
        wasm_bindgen_version: impl Into<String>,
    ) -> Self {
        Self::WasmBindgen(WasmBindgenPublicAsset {
            id: id.into(),
            label: label.into(),
            package: package.into(),
            wasm_file: wasm_file.into(),
            no_default_features: false,
            features: String::new(),
            target_dir: None,
            out_dir: out_dir.into(),
            out_name: out_name.into(),
            wasm_bindgen_version: wasm_bindgen_version.into(),
        })
    }

    /// Validates this asset for the named project and configuration source.
    pub fn validate(&self, source: &str, project_id: &str) -> DevResult {
        match self {
            Self::WasmBindgen(asset) => asset.validate(source, project_id),
        }
    }

    /// Controls whether Cargo default features are disabled for this asset build.
    pub fn with_no_default_features(mut self, no_default_features: bool) -> Self {
        match &mut self {
            Self::WasmBindgen(asset) => {
                asset.no_default_features = no_default_features;
            }
        }
        self
    }

    /// Sets the comma-separated Cargo feature list used for this asset build.
    pub fn with_features(mut self, features: impl Into<String>) -> Self {
        match &mut self {
            Self::WasmBindgen(asset) => {
                asset.features = features.into();
            }
        }
        self
    }

    /// Sets the Cargo target directory relative to the project root.
    pub fn with_target_dir(mut self, target_dir: impl Into<String>) -> Self {
        match &mut self {
            Self::WasmBindgen(asset) => {
                asset.target_dir = Some(target_dir.into());
            }
        }
        self
    }

    fn id(&self) -> &str {
        match self {
            Self::WasmBindgen(asset) => &asset.id,
        }
    }

    fn package(&self) -> &str {
        match self {
            Self::WasmBindgen(asset) => &asset.package,
        }
    }
}

impl WasmBindgenPublicAsset {
    fn validate(&self, source: &str, project_id: &str) -> DevResult {
        ensure!(
            !self.id.trim().is_empty(),
            "{source} project `{project_id}` has a wasm-bindgen asset with an empty id"
        );
        ensure!(
            !self.label.trim().is_empty(),
            "{source} project `{project_id}` asset `{}` has an empty label",
            self.id
        );
        ensure!(
            !self.package.trim().is_empty(),
            "{source} project `{project_id}` asset `{}` has an empty package",
            self.id
        );
        ensure!(
            !self.wasm_file.trim().is_empty(),
            "{source} project `{project_id}` asset `{}` has an empty wasm_file",
            self.id
        );
        ensure!(
            !self.out_dir.is_empty(),
            "{source} project `{project_id}` asset `{}` must declare out_dir",
            self.id
        );
        ensure!(
            !self.out_name.trim().is_empty(),
            "{source} project `{project_id}` asset `{}` has an empty out_name",
            self.id
        );
        ensure!(
            !self.wasm_bindgen_version.trim().is_empty(),
            "{source} project `{project_id}` asset `{}` has an empty wasm_bindgen_version",
            self.id
        );
        if let Some(target_dir) = &self.target_dir {
            let target_dir = Path::new(target_dir);
            ensure!(
                target_dir.is_relative()
                    && target_dir
                        .components()
                        .all(|component| matches!(component, std::path::Component::Normal(_))),
                "{source} project `{project_id}` asset `{}` has an invalid target_dir",
                self.id
            );
        }
        Ok(())
    }
}

impl WorkspacePaths {
    /// Returns the Cargo workspace root.
    pub fn workspace_root(&self) -> &Path {
        &self.workspace_root
    }

    /// Returns the project repository root.
    pub fn project_root(&self) -> &Path {
        &self.project_root
    }

    /// Returns the web-client root.
    pub fn web_root(&self) -> &Path {
        &self.web_root
    }
}

/// Runs the selected development task for `profile`.
pub fn run_project(profile: ProjectProfile, manifest_dir: impl AsRef<Path>) -> DevResult {
    color_eyre::install()?;
    match AppCli::parse().command {
        AppCommand::Watch(command) => {
            let profile = activate_optional_public_assets(
                profile,
                command.run.optional_assets.include_optional_assets,
            );
            let paths = resolve_paths_from_manifest_dir(&profile, manifest_dir.as_ref())?;
            run_profile_with_backend_reload(
                &profile,
                &paths,
                command.run.release,
                RunMode::Watch,
                !command.no_backend_reload,
            )
        }
        AppCommand::Serve(command) => {
            let profile = activate_optional_public_assets(
                profile,
                command.optional_assets.include_optional_assets,
            );
            let paths = resolve_paths_from_manifest_dir(&profile, manifest_dir.as_ref())?;
            run_profile(&profile, &paths, command.release, RunMode::Serve)
        }
        AppCommand::Build(command) => {
            let profile = activate_optional_public_assets(
                profile,
                command.optional_assets.include_optional_assets,
            );
            let paths = resolve_paths_from_manifest_dir(&profile, manifest_dir.as_ref())?;
            build_profile(&profile, &paths, true)
        }
        AppCommand::BuildPublicAsset(command) => {
            let paths = resolve_paths_from_manifest_dir(&profile, manifest_dir.as_ref())?;
            let asset = profile
                .public_assets
                .iter()
                .chain(&profile.optional_public_assets)
                .find(|asset| asset.id() == command.id)
                .ok_or_else(|| {
                    color_eyre::eyre::eyre!(
                        "project `{}` has no public asset named `{}`",
                        profile.app_id,
                        command.id
                    )
                })?;
            match asset {
                ProjectPublicAsset::WasmBindgen(asset) => build_wasm_bindgen_public_asset(
                    &profile,
                    &paths,
                    asset,
                    command.release,
                    command.target_dir.as_deref(),
                ),
            }
        }
    }
}

fn activate_optional_public_assets(
    mut profile: ProjectProfile,
    include_optional_assets: bool,
) -> ProjectProfile {
    if include_optional_assets {
        profile
            .public_assets
            .append(&mut profile.optional_public_assets);
    }
    profile
}

/// Resolves project paths by walking upward from a Cargo manifest directory.
pub fn resolve_paths_from_manifest_dir(
    profile: &ProjectProfile,
    manifest_dir: &Path,
) -> DevResult<WorkspacePaths> {
    let project_root = find_project_root_from_manifest_dir(manifest_dir, &profile.web_dir)?;
    let workspace_root = find_workspace_root(&project_root)?;
    let web_root = project_root.join(&profile.web_dir);
    validate_paths(&project_root, &web_root)?;
    Ok(WorkspacePaths {
        workspace_root,
        project_root,
        web_root,
    })
}

/// Resolves project paths from a repository directory beneath the current workspace.
pub fn resolve_paths_from_workspace_project(
    profile: &ProjectProfile,
    repo_dir: &str,
) -> DevResult<WorkspacePaths> {
    let cwd = env::current_dir().wrap_err("failed to resolve current directory")?;
    let workspace_root = find_workspace_root(&cwd)?;
    let project_root = workspace_root.join(repo_dir);
    let web_root = project_root.join(&profile.web_dir);
    validate_paths(&project_root, &web_root)?;
    Ok(WorkspacePaths {
        workspace_root,
        project_root,
        web_root,
    })
}

/// Prepares a project and runs it in the requested mode.
pub fn run_profile(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    release: bool,
    mode: RunMode,
) -> DevResult {
    run_profile_with_backend_reload(profile, paths, release, mode, true)
}

fn run_profile_with_backend_reload(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    release: bool,
    mode: RunMode,
    backend_reload: bool,
) -> DevResult {
    install_node_dependencies(&paths.web_root)?;
    bootstrap_project_dev_services(profile, paths, release)?;

    match mode {
        RunMode::Watch => {
            build_project_public_assets(profile, paths, release)?;
            watch_project(profile, paths, release, backend_reload)
        }
        RunMode::Serve => {
            build_project_public_assets(profile, paths, release)?;
            build_react(&paths.web_root)?;
            start_backend(profile, paths, release)
        }
    }
}

/// Builds registered public assets and the React client without starting the backend.
pub fn build_profile(profile: &ProjectProfile, paths: &WorkspacePaths, release: bool) -> DevResult {
    install_node_dependencies(&paths.web_root)?;
    build_project_public_assets(profile, paths, release)?;
    build_react(&paths.web_root)
}

fn find_project_root_from_manifest_dir(manifest_dir: &Path, web_dir: &str) -> DevResult<PathBuf> {
    let start = if manifest_dir.is_absolute() {
        manifest_dir.to_path_buf()
    } else {
        env::current_dir()
            .wrap_err("failed to resolve current directory")?
            .join(manifest_dir)
    };

    let mut current = Some(start.as_path());
    while let Some(candidate) = current {
        if candidate.join("Cargo.toml").is_file()
            && candidate.join(web_dir).join("package.json").is_file()
        {
            return Ok(candidate.to_path_buf());
        }
        current = candidate.parent();
    }

    bail!(
        "failed to resolve app project root from {}",
        manifest_dir.display()
    );
}

fn validate_paths(project_root: &Path, web_root: &Path) -> DevResult {
    if !project_root.join("Cargo.toml").is_file() {
        bail!(
            "project manifest is missing at {}",
            project_root.join("Cargo.toml").display()
        );
    }
    if !web_root.join("package.json").is_file() {
        bail!(
            "web package manifest is missing at {}",
            web_root.join("package.json").display()
        );
    }
    Ok(())
}

#[cfg(feature = "btcpay")]
fn bootstrap_project_dev_services(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    release: bool,
) -> DevResult {
    let Some(btcpay_profile) = profile.btcpay.clone() else {
        return Ok(());
    };
    if release {
        return Ok(());
    }

    let options = LocalBtcpayBootstrapOptions::new(btcpay_profile, &paths.project_root);
    let summary = bootstrap_local_btcpay(&options)
        .map_err(|error| color_eyre::eyre::eyre!("failed to bootstrap local BTCPay: {error:#}"))?;
    eprintln!(
        "BTCPay local dev bootstrap ready for {}: {} (store {}, api {}, webhook {}, env {})",
        summary.app_display_name,
        summary.url,
        summary.store_id,
        summary.api_key_masked,
        summary.webhook_secret_masked,
        summary.env_file.display()
    );
    Ok(())
}

#[cfg(not(feature = "btcpay"))]
fn bootstrap_project_dev_services(
    _profile: &ProjectProfile,
    _paths: &WorkspacePaths,
    _release: bool,
) -> DevResult {
    Ok(())
}

fn find_workspace_root(start: &Path) -> DevResult<PathBuf> {
    let mut nearest_package = None;

    for candidate in start.ancestors() {
        let manifest_path = candidate.join("Cargo.toml");
        if !manifest_path.is_file() {
            continue;
        }

        let source = fs::read_to_string(&manifest_path).wrap_err_with(|| {
            format!(
                "failed to read Cargo manifest at {}",
                manifest_path.display()
            )
        })?;
        let manifest = toml::from_str::<toml::Table>(&source).wrap_err_with(|| {
            format!(
                "failed to parse Cargo manifest at {}",
                manifest_path.display()
            )
        })?;

        if manifest.contains_key("workspace") {
            return Ok(candidate.to_path_buf());
        }
        if nearest_package.is_none() && manifest.contains_key("package") {
            nearest_package = Some(candidate.to_path_buf());
        }
    }

    nearest_package.ok_or_else(|| {
        color_eyre::eyre::eyre!(
            "failed to find a Cargo workspace or package manifest above {}",
            start.display()
        )
    })
}

fn install_node_dependencies(web_root: &Path) -> DevResult {
    if web_root.join("node_modules").is_dir() {
        return Ok(());
    }

    run_command("Node dependency install", npm(), &["ci"], web_root, &[])
}

fn build_react(web_root: &Path) -> DevResult {
    let script = resolve_build_script(web_root)?;
    run_command("Web build", npm(), &["run", script], web_root, &[])
}

fn build_project_public_assets(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    release: bool,
) -> DevResult {
    for asset in &profile.public_assets {
        match asset {
            ProjectPublicAsset::WasmBindgen(asset) => {
                build_wasm_bindgen_public_asset(profile, paths, asset, release, None)?;
            }
        }
    }

    Ok(())
}

fn resolve_public_asset_target_dir(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    asset: &WasmBindgenPublicAsset,
    target_dir_override: Option<&Path>,
) -> DevResult<PathBuf> {
    if let Some(target_dir) = target_dir_override {
        ensure!(
            target_dir.is_absolute()
                && target_dir.components().all(|component| matches!(
                    component,
                    std::path::Component::Prefix(_)
                        | std::path::Component::RootDir
                        | std::path::Component::Normal(_)
                ))
                && target_dir
                    .components()
                    .any(|component| matches!(component, std::path::Component::Normal(_))),
            "public asset --target-dir must be a nonempty absolute normal path"
        );
        return Ok(target_dir.to_path_buf());
    }
    Ok(asset.target_dir.as_ref().map_or_else(
        || {
            paths
                .project_root
                .join("target")
                .join(format!("{}-dev-{}-build", profile.app_id, asset.id))
        },
        |target_dir| paths.project_root.join(target_dir),
    ))
}

fn build_wasm_bindgen_public_asset(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    asset: &WasmBindgenPublicAsset,
    release: bool,
    target_dir_override: Option<&Path>,
) -> DevResult {
    let target_dir = resolve_public_asset_target_dir(profile, paths, asset, target_dir_override)?;
    let target_dir_arg = path_arg(&target_dir)?;
    let mut args = vec![
        "build",
        "--lib",
        "--package",
        asset.package.as_str(),
        "--locked",
        "--target",
        "wasm32-unknown-unknown",
    ];
    if release {
        args.push("--release");
    }
    if asset.no_default_features {
        args.push("--no-default-features");
    }
    if !asset.features.trim().is_empty() {
        args.push("--features");
        args.push(asset.features.as_str());
    }
    args.push("--target-dir");
    args.push(target_dir_arg);

    run_command(
        format!("{} WASM build", asset.label).as_str(),
        cargo(),
        &args,
        &paths.project_root,
        &[],
    )?;

    let wasm_input = target_dir
        .join("wasm32-unknown-unknown")
        .join(if release { "release" } else { "debug" })
        .join(&asset.wasm_file);
    if !wasm_input.is_file() {
        bail!(
            "missing expected {} WASM at {}",
            asset.label,
            wasm_input.display()
        );
    }

    let mut out_dir = paths.web_root.clone();
    for segment in &asset.out_dir {
        out_dir.push(segment);
    }
    let out_parent = out_dir.parent().ok_or_else(|| {
        color_eyre::eyre::eyre!(
            "{} WASM output has no parent directory: {}",
            asset.label,
            out_dir.display()
        )
    })?;
    fs::create_dir_all(out_parent).wrap_err_with(|| {
        format!(
            "failed to create {} WASM output parent at {}",
            asset.label,
            out_parent.display()
        )
    })?;
    let out_name = out_dir.file_name().ok_or_else(|| {
        color_eyre::eyre::eyre!(
            "{} WASM output has no directory name: {}",
            asset.label,
            out_dir.display()
        )
    })?;
    let staging_dir = out_parent.join(format!(".{}.building", out_name.to_string_lossy()));
    if staging_dir.exists() {
        fs::remove_dir_all(&staging_dir).wrap_err_with(|| {
            format!(
                "failed to remove stale {} WASM staging output at {}",
                asset.label,
                staging_dir.display()
            )
        })?;
    }
    fs::create_dir_all(&staging_dir).wrap_err_with(|| {
        format!(
            "failed to create {} WASM staging output at {}",
            asset.label,
            staging_dir.display()
        )
    })?;

    let wasm_input_arg = path_arg(&wasm_input)?;
    let staging_dir_arg = path_arg(&staging_dir)?;
    if let Err(error) = run_command(
        format!("{} wasm-bindgen", asset.label).as_str(),
        resolve_wasm_bindgen(&asset.wasm_bindgen_version)?,
        &[
            wasm_input_arg,
            "--target",
            "web",
            "--out-dir",
            staging_dir_arg,
            "--out-name",
            asset.out_name.as_str(),
        ],
        &paths.project_root,
        &[],
    ) {
        let _ = fs::remove_dir_all(&staging_dir);
        return Err(error);
    }

    if out_dir.exists() {
        fs::remove_dir_all(&out_dir).wrap_err_with(|| {
            format!(
                "failed to replace previous {} WASM output at {}",
                asset.label,
                out_dir.display()
            )
        })?;
    }
    fs::rename(&staging_dir, &out_dir).wrap_err_with(|| {
        format!(
            "failed to activate {} WASM output from {} to {}",
            asset.label,
            staging_dir.display(),
            out_dir.display()
        )
    })
}

fn resolve_build_script(web_root: &Path) -> DevResult<&'static str> {
    let package_json_path = web_root.join("package.json");
    let package_json = std::fs::read_to_string(&package_json_path)
        .wrap_err_with(|| format!("failed to read {}", package_json_path.display()))?;
    let package_json: Value = serde_json::from_str(&package_json)
        .wrap_err_with(|| format!("failed to parse {}", package_json_path.display()))?;
    let scripts = package_json
        .get("scripts")
        .and_then(Value::as_object)
        .ok_or_else(|| color_eyre::eyre::eyre!("package.json has no scripts object"))?;

    if scripts.contains_key("build") {
        return Ok("build");
    }
    if scripts.contains_key("build:web") {
        return Ok("build:web");
    }

    bail!(
        "{} must define either `build` or `build:web`",
        package_json_path.display()
    );
}

fn start_backend(profile: &ProjectProfile, paths: &WorkspacePaths, release: bool) -> DevResult {
    let args = backend_args(profile, release);
    let envs = backend_envs(profile);
    run_command("Rust backend", cargo(), &args, &paths.project_root, &envs)
}

fn watch_project(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    release: bool,
    backend_reload: bool,
) -> DevResult {
    let api_addr = api_addr(profile)?;
    let backend_envs = backend_envs(profile);
    let mut backend = if backend_reload {
        let artifact = backend_executable_path(profile, paths, release);
        // The last artifact can predate source changes made while the watcher
        // was stopped. Build once before launching it so the first readiness
        // probe always exercises the current owner pipeline.
        let args = backend_build_args(profile, release);
        run_command(
            "initial Rust backend build",
            cargo(),
            &args,
            &paths.project_root,
            &backend_envs,
        )?;
        let active_stamp = backend_artifact_stamp(&artifact)?;
        let active_image = backend_runtime_image_path(profile, &artifact, 0);
        copy_backend_runtime_image(&artifact, &active_image)?;
        let mut process = spawn_command(
            "Rust backend",
            active_image.as_os_str().to_os_string(),
            &[] as &[&str],
            &paths.project_root,
            &[],
        )?;
        wait_for_backend_ready(
            &mut process,
            api_addr,
            profile.backend_ready_timeout,
            profile.backend_ready_path.as_deref(),
        )?;

        let watchexec = resolve_watchexec()?;
        let watch_paths = resolve_backend_watch_paths(profile, paths)?;
        let backend_args = backend_watchexec_args(profile, paths, &watch_paths, release);
        let builder = spawn_command(
            "Rust backend build watcher",
            watchexec,
            &backend_args,
            &paths.project_root,
            &backend_envs,
        )?;
        BackendWatchRuntime {
            process,
            builder: Some(builder),
            artifact: Some(artifact),
            active_image: Some(active_image),
            active_stamp: Some(active_stamp),
            generation: 0,
        }
    } else {
        let backend_args = backend_args(profile, release);
        let mut process = spawn_command(
            "Rust backend",
            cargo(),
            &backend_args,
            &paths.project_root,
            &backend_envs,
        )?;
        wait_for_backend_ready(
            &mut process,
            api_addr,
            profile.backend_ready_timeout,
            profile.backend_ready_path.as_deref(),
        )?;
        BackendWatchRuntime {
            process,
            builder: None,
            artifact: None,
            active_image: None,
            active_stamp: None,
            generation: 0,
        }
    };

    let mut public_asset_watchers = spawn_public_asset_watchers(profile, paths, release)?;
    let backend_origin = format!("http://127.0.0.1:{}", api_addr.port());
    let web_envs = web_dev_envs(profile, &backend_origin);
    let mut web = spawn_command(
        "web dev server",
        npm(),
        &["run", "dev"],
        &paths.web_root,
        &web_envs,
    )?;

    wait_for_watch_processes(
        profile,
        paths,
        api_addr,
        &mut backend,
        &mut web,
        &mut public_asset_watchers,
    )
}

fn wait_for_backend_ready(
    backend: &mut ManagedChild,
    api_addr: SocketAddr,
    ready_timeout: Duration,
    ready_path: Option<&str>,
) -> DevResult {
    let ready_addr = SocketAddr::from(([127, 0, 0, 1], api_addr.port()));
    let started_at = Instant::now();

    loop {
        if let Some(status) = backend.try_wait().wrap_err("failed to poll Rust backend")? {
            if status.success() {
                bail!(
                    "Rust backend exited before it became ready at {}",
                    ready_addr
                );
            }
            bail!(
                "Rust backend exited with status {:?} before it became ready at {}",
                status.code(),
                ready_addr
            );
        }

        let readiness = match ready_path {
            Some(path) => probe_backend_http(ready_addr, path),
            None => {
                TcpStream::connect_timeout(&ready_addr, BACKEND_READY_CONNECT_TIMEOUT).map(|_| ())
            }
        };
        let last_error = match readiness {
            Ok(()) => return Ok(()),
            Err(error) => error,
        };

        if started_at.elapsed() >= ready_timeout {
            backend.terminate();
            bail!(
                "Rust backend did not become ready at {} within {:?}: {}",
                ready_addr,
                ready_timeout,
                last_error
            );
        }

        thread::sleep(BACKEND_READY_POLL_INTERVAL);
    }
}

fn probe_backend_http(ready_addr: SocketAddr, path: &str) -> std::io::Result<()> {
    let mut stream = TcpStream::connect_timeout(&ready_addr, BACKEND_READY_CONNECT_TIMEOUT)?;
    stream.set_read_timeout(Some(BACKEND_READY_CONNECT_TIMEOUT))?;
    stream.set_write_timeout(Some(BACKEND_READY_CONNECT_TIMEOUT))?;
    write!(
        stream,
        "GET {path} HTTP/1.1\r\nHost: {ready_addr}\r\nConnection: close\r\n\r\n"
    )?;

    let mut prefix = [0_u8; 5];
    stream.read_exact(&mut prefix)?;
    if prefix == *b"HTTP/" {
        Ok(())
    } else {
        Err(std::io::Error::new(
            std::io::ErrorKind::InvalidData,
            "backend readiness response is not HTTP",
        ))
    }
}

fn backend_args(profile: &ProjectProfile, release: bool) -> Vec<&str> {
    let mut args = vec!["run", "--bin", profile.bin_target(), "--locked"];
    if release {
        args.push("--release");
    }
    args
}

fn backend_build_args(profile: &ProjectProfile, release: bool) -> Vec<&str> {
    let mut args = vec!["build", "--bin", profile.bin_target(), "--locked"];
    if release {
        args.push("--release");
    }
    args
}

fn backend_executable_path(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    release: bool,
) -> PathBuf {
    let target_root = profile.backend_target_dir.as_ref().map_or_else(
        || paths.workspace_root.join("target"),
        |target_dir| {
            let target_dir = Path::new(target_dir);
            if target_dir.is_absolute() {
                target_dir.to_path_buf()
            } else {
                paths.project_root.join(target_dir)
            }
        },
    );
    target_root
        .join(if release { "release" } else { "debug" })
        .join(format!(
            "{}{}",
            profile.bin_target(),
            env::consts::EXE_SUFFIX
        ))
}

fn backend_artifact_stamp(path: &Path) -> DevResult<BackendArtifactStamp> {
    backend_artifact_stamp_if_present(path)?
        .ok_or_else(|| color_eyre::eyre::eyre!("Rust backend is missing at {}", path.display()))
}

fn backend_artifact_stamp_if_present(path: &Path) -> DevResult<Option<BackendArtifactStamp>> {
    let metadata = match fs::metadata(path) {
        Ok(metadata) => metadata,
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => return Ok(None),
        Err(error) => {
            return Err(error)
                .wrap_err_with(|| format!("failed to inspect Rust backend at {}", path.display()));
        }
    };
    Ok(Some(BackendArtifactStamp {
        modified: metadata.modified().wrap_err_with(|| {
            format!(
                "failed to read Rust backend timestamp at {}",
                path.display()
            )
        })?,
        length: metadata.len(),
    }))
}

fn backend_runtime_image_path(
    profile: &ProjectProfile,
    artifact: &Path,
    generation: u64,
) -> PathBuf {
    artifact
        .parent()
        .unwrap_or_else(|| Path::new("."))
        .join(format!(
            ".{}-ch-rds-{}-{generation}{}",
            profile.bin_target(),
            std::process::id(),
            env::consts::EXE_SUFFIX
        ))
}

fn copy_backend_runtime_image(artifact: &Path, image: &Path) -> DevResult {
    fs::copy(artifact, image).wrap_err_with(|| {
        format!(
            "failed to prepare Rust backend runtime image from {} to {}",
            artifact.display(),
            image.display()
        )
    })?;
    Ok(())
}

fn backend_watchexec_args(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    watch_paths: &BackendWatchPaths,
    release: bool,
) -> Vec<OsString> {
    let mut args = vec![
        OsString::from("--on-busy-update=queue"),
        OsString::from(format!("--debounce={WATCH_DEBOUNCE}")),
        OsString::from("--shell=none"),
        OsString::from("--emit-events-to=none"),
        OsString::from("--project-origin"),
        paths.project_root.as_os_str().to_os_string(),
        OsString::from("--exts"),
        OsString::from("rs,toml,lock,sql"),
    ];

    for path in &watch_paths.paths {
        args.push(OsString::from("--watch"));
        args.push(path.as_os_str().to_os_string());
    }

    args.push(OsString::from("--"));
    args.push(cargo());
    args.extend(
        backend_build_args(profile, release)
            .into_iter()
            .map(OsString::from),
    );
    args
}

fn public_asset_watchexec_args(
    paths: &WorkspacePaths,
    asset: &ProjectPublicAsset,
    watch_paths: &BackendWatchPaths,
    release: bool,
) -> DevResult<Vec<OsString>> {
    let mut args = vec![
        OsString::from("--on-busy-update=queue"),
        OsString::from(format!("--debounce={WATCH_DEBOUNCE}")),
        OsString::from("--shell=none"),
        OsString::from("--emit-events-to=none"),
        OsString::from("--project-origin"),
        paths.project_root.as_os_str().to_os_string(),
        OsString::from("--exts"),
        OsString::from("rs,toml,lock"),
    ];

    for path in &watch_paths.paths {
        args.push(OsString::from("--watch"));
        args.push(path.as_os_str().to_os_string());
    }

    args.push(OsString::from("--"));
    args.push(
        env::current_exe()
            .wrap_err("failed to resolve the project task executable")?
            .into_os_string(),
    );
    args.push(OsString::from("build-public-asset"));
    args.push(OsString::from("--id"));
    args.push(OsString::from(asset.id()));
    if release {
        args.push(OsString::from("--release"));
    }
    Ok(args)
}

fn spawn_public_asset_watchers(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    release: bool,
) -> DevResult<Vec<ManagedChild>> {
    if profile.public_assets.is_empty() {
        return Ok(Vec::new());
    }

    let watchexec = resolve_watchexec()?;
    let metadata = load_cargo_metadata(paths, "public asset reloads")?;
    let mut watchers = Vec::with_capacity(profile.public_assets.len());
    for asset in &profile.public_assets {
        let watch_paths = package_watch_paths_from_metadata(&metadata, asset.package())?;
        let args = public_asset_watchexec_args(paths, asset, &watch_paths, release)?;
        watchers.push(spawn_command(
            format!("{} public asset watcher", asset.id()).as_str(),
            watchexec.clone(),
            &args,
            &paths.project_root,
            &[],
        )?);
    }
    Ok(watchers)
}

fn resolve_watchexec() -> DevResult<OsString> {
    let executable = find_on_path("watchexec").ok_or_else(|| {
        color_eyre::eyre::eyre!(
            "Watchexec is required for backend reloads; install it with `cargo install watchexec-cli --version 2.5.1 --locked`"
        )
    })?;
    let output = ProcessCommand::new(&executable)
        .arg("--version")
        .output()
        .wrap_err("failed to check the installed Watchexec version")?;
    if output.status.success() {
        return Ok(executable.into_os_string());
    }

    let stderr = String::from_utf8_lossy(&output.stderr);
    let details = stderr.trim();
    if details.is_empty() {
        bail!(
            "Watchexec is required for backend reloads; install it with `cargo install watchexec-cli --version 2.5.1 --locked`"
        );
    }

    bail!(
        "Watchexec is required for backend reloads; install it with `cargo install watchexec-cli --version 2.5.1 --locked`\n\n{details}"
    );
}

fn resolve_backend_watch_paths(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
) -> DevResult<BackendWatchPaths> {
    let metadata = load_cargo_metadata(paths, "backend reloads")?;
    backend_watch_paths_from_metadata(&metadata, profile.bin_target())
}

fn load_cargo_metadata(paths: &WorkspacePaths, purpose: &str) -> DevResult<CargoMetadata> {
    let output = ProcessCommand::new(cargo())
        .args(["metadata", "--format-version=1", "--locked"])
        .current_dir(&paths.project_root)
        .output()
        .wrap_err_with(|| format!("failed to read Cargo metadata for {purpose}"))?;
    if !output.status.success() {
        let details = String::from_utf8_lossy(&output.stderr);
        bail!("Cargo metadata failed for {purpose}: {}", details.trim());
    }

    serde_json::from_slice::<CargoMetadata>(&output.stdout)
        .wrap_err_with(|| format!("failed to parse Cargo metadata for {purpose}"))
}

fn backend_watch_paths_from_metadata(
    metadata: &CargoMetadata,
    bin_target: &str,
) -> DevResult<BackendWatchPaths> {
    let root_ids = metadata
        .packages
        .iter()
        .filter(|package| {
            package.targets.iter().any(|target| {
                target.name == bin_target && target.kind.iter().any(|kind| kind == "bin")
            })
        })
        .map(|package| package.id.as_str())
        .collect::<Vec<_>>();
    ensure!(
        !root_ids.is_empty(),
        "Cargo metadata contains no binary target named `{bin_target}`"
    );

    watch_paths_from_metadata_roots(metadata, root_ids)
}

fn package_watch_paths_from_metadata(
    metadata: &CargoMetadata,
    package_name: &str,
) -> DevResult<BackendWatchPaths> {
    let root_ids = metadata
        .packages
        .iter()
        .filter(|package| package.name == package_name)
        .map(|package| package.id.as_str())
        .collect::<Vec<_>>();
    ensure!(
        !root_ids.is_empty(),
        "Cargo metadata contains no package named `{package_name}`"
    );

    watch_paths_from_metadata_roots(metadata, root_ids)
}

fn watch_paths_from_metadata_roots<'a>(
    metadata: &'a CargoMetadata,
    root_ids: Vec<&'a str>,
) -> DevResult<BackendWatchPaths> {
    let resolve = metadata
        .resolve
        .as_ref()
        .ok_or_else(|| color_eyre::eyre::eyre!("Cargo metadata did not include a resolve graph"))?;

    let nodes = resolve
        .nodes
        .iter()
        .map(|node| (node.id.as_str(), node))
        .collect::<HashMap<_, _>>();
    let mut reachable = BTreeSet::new();
    let mut pending = root_ids.into_iter().collect::<VecDeque<_>>();
    while let Some(package_id) = pending.pop_front() {
        if !reachable.insert(package_id) {
            continue;
        }
        if let Some(node) = nodes.get(package_id) {
            pending.extend(node.deps.iter().map(|dependency| dependency.pkg.as_str()));
        }
    }

    let mut watch_paths = BTreeSet::new();
    for package in metadata
        .packages
        .iter()
        .filter(|package| package.source.is_none() && reachable.contains(package.id.as_str()))
    {
        let package_root = package.manifest_path.parent().ok_or_else(|| {
            color_eyre::eyre::eyre!(
                "Cargo package manifest has no parent: {}",
                package.manifest_path.display()
            )
        })?;
        insert_existing_watch_path(&mut watch_paths, &package.manifest_path)?;

        let workspace_root = find_workspace_root(package_root)?;
        insert_existing_watch_path(&mut watch_paths, &workspace_root.join("Cargo.toml"))?;
        for workspace_file in ["Cargo.lock", "rust-toolchain.toml", ".rust-version"] {
            let workspace_file = workspace_root.join(workspace_file);
            if workspace_file.is_file() {
                insert_existing_watch_path(&mut watch_paths, &workspace_file)?;
            }
        }
        let cargo_config_dir = workspace_root.join(".cargo");
        if cargo_config_dir.is_dir() {
            insert_existing_watch_path(&mut watch_paths, &cargo_config_dir)?;
        }

        let conventional_source_root = package_root.join("src");
        if conventional_source_root.is_dir() {
            insert_existing_watch_path(&mut watch_paths, &conventional_source_root)?;
        }
        for target in &package.targets {
            if !target.src_path.starts_with(&conventional_source_root) && target.src_path.is_file()
            {
                insert_existing_watch_path(&mut watch_paths, &target.src_path)?;
            }
        }

        let migrations = package_root.join("migrations");
        if migrations.is_dir() {
            insert_existing_watch_path(&mut watch_paths, &migrations)?;
        }
    }

    Ok(BackendWatchPaths {
        paths: watch_paths.into_iter().collect(),
    })
}

fn insert_existing_watch_path(paths: &mut BTreeSet<PathBuf>, path: &Path) -> DevResult {
    let canonical = path
        .canonicalize()
        .wrap_err_with(|| format!("failed to resolve backend watch path {}", path.display()))?;
    paths.insert(canonical);
    Ok(())
}

fn api_addr(profile: &ProjectProfile) -> DevResult<SocketAddr> {
    profile.api_addr.parse::<SocketAddr>().wrap_err_with(|| {
        format!(
            "invalid site address `{}` for project `{}`",
            profile.api_addr, profile.app_id
        )
    })
}

fn web_dev_envs(profile: &ProjectProfile, backend_origin: &str) -> Vec<(String, String)> {
    let mut envs = Vec::new();
    if let Some(origin_env) = &profile.web_backend_origin_env {
        envs.push((origin_env.clone(), backend_origin.to_string()));
    }
    envs
}

fn backend_envs(profile: &ProjectProfile) -> Vec<(String, String)> {
    profile
        .backend_target_dir
        .as_ref()
        .map(|target_dir| vec![("CARGO_TARGET_DIR".to_string(), target_dir.clone())])
        .unwrap_or_default()
}

fn wait_for_watch_processes(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    api_addr: SocketAddr,
    backend: &mut BackendWatchRuntime,
    web: &mut ManagedChild,
    public_asset_watchers: &mut [ManagedChild],
) -> DevResult {
    loop {
        if let Some(status) = backend
            .process
            .try_wait()
            .wrap_err("failed to poll Rust backend")?
        {
            if status.success() {
                bail!("Rust backend exited before the web dev server");
            }
            bail!("Rust backend exited with status {:?}", status.code());
        }

        if let Some(builder) = backend.builder.as_mut()
            && let Some(status) = builder
                .try_wait()
                .wrap_err("failed to poll Rust backend build watcher")?
        {
            bail!(
                "Rust backend build watcher exited unexpectedly with status {:?}",
                status.code()
            );
        }

        refresh_backend_after_successful_build(profile, paths, api_addr, backend)?;

        if let Some(status) = web.try_wait().wrap_err("failed to poll web dev server")? {
            if status.success() {
                return Ok(());
            }
            bail!("web dev server exited with status {:?}", status.code());
        }

        let mut watcher_exit = None;
        for watcher in public_asset_watchers.iter_mut() {
            if let Some(status) = watcher
                .try_wait()
                .wrap_err("failed to poll a public asset watcher")?
            {
                watcher_exit = Some(status);
                break;
            }
        }
        if let Some(status) = watcher_exit {
            bail!(
                "public asset watcher exited unexpectedly with status {:?}",
                status.code()
            );
        }

        thread::sleep(Duration::from_millis(250));
    }
}

fn refresh_backend_after_successful_build(
    profile: &ProjectProfile,
    paths: &WorkspacePaths,
    api_addr: SocketAddr,
    backend: &mut BackendWatchRuntime,
) -> DevResult {
    let Some(artifact) = backend.artifact.as_ref() else {
        return Ok(());
    };
    let Some(candidate_stamp) = backend_artifact_stamp_if_present(artifact)? else {
        // Cargo may temporarily remove the final executable while rustc links a
        // replacement. The build watcher still owns that transition, so keep
        // serving the last successful runtime image until the artifact appears.
        return Ok(());
    };
    if backend.active_stamp == Some(candidate_stamp) {
        return Ok(());
    }

    let candidate_generation = backend.generation.saturating_add(1);
    let candidate_image = backend_runtime_image_path(profile, artifact, candidate_generation);
    copy_backend_runtime_image(artifact, &candidate_image)?;
    backend.process.terminate();
    let candidate = spawn_command(
        "rebuilt Rust backend",
        candidate_image.as_os_str().to_os_string(),
        &[] as &[&str],
        &paths.project_root,
        &[],
    );
    let candidate = candidate.and_then(|mut candidate| {
        wait_for_backend_ready(
            &mut candidate,
            api_addr,
            profile.backend_ready_timeout,
            profile.backend_ready_path.as_deref(),
        )
        .map(|()| candidate)
    });

    match candidate {
        Ok(candidate) => {
            remove_backend_runtime_image(backend.active_image.replace(candidate_image));
            backend.process = candidate;
            backend.active_stamp = Some(candidate_stamp);
            backend.generation = candidate_generation;
            eprintln!(
                "Activated rebuilt Rust backend generation {} from {}",
                backend.generation,
                artifact.display()
            );
            Ok(())
        }
        Err(error) => {
            remove_backend_runtime_image(Some(candidate_image));
            let fallback_image = backend.active_image.as_ref().ok_or_else(|| {
                color_eyre::eyre::eyre!(
                    "rebuilt Rust backend failed and no last successful runtime image exists"
                )
            })?;
            let mut fallback = spawn_command(
                "last successful Rust backend",
                fallback_image.as_os_str().to_os_string(),
                &[] as &[&str],
                &paths.project_root,
                &[],
            )?;
            wait_for_backend_ready(
                &mut fallback,
                api_addr,
                profile.backend_ready_timeout,
                profile.backend_ready_path.as_deref(),
            )?;
            backend.process = fallback;
            backend.active_stamp = Some(candidate_stamp);
            eprintln!(
                "Rebuilt Rust backend did not become ready: {error:#}. Continuing with the last successful backend until another build succeeds."
            );
            Ok(())
        }
    }
}

impl Drop for BackendWatchRuntime {
    fn drop(&mut self) {
        self.process.terminate();
        if let Some(builder) = self.builder.as_mut() {
            builder.terminate();
        }
        remove_backend_runtime_image(self.active_image.take());
    }
}

fn remove_backend_runtime_image(path: Option<PathBuf>) {
    if let Some(path) = path {
        let _ = fs::remove_file(path);
    }
}

fn run_command<S: AsRef<OsStr>>(
    label: &str,
    executable: OsString,
    args: &[S],
    cwd: &Path,
    envs: &[(String, String)],
) -> DevResult {
    let mut child = spawn_command(label, executable, args, cwd, envs)?;
    let status = child
        .wait()
        .wrap_err_with(|| format!("failed to wait for {label}"))?;
    if status.success() {
        return Ok(());
    }

    bail!("{label} exited with status {:?}", status.code());
}

fn spawn_command<S: AsRef<OsStr>>(
    label: &str,
    executable: OsString,
    args: &[S],
    cwd: &Path,
    envs: &[(String, String)],
) -> DevResult<ManagedChild> {
    let mut command = ProcessCommand::new(executable);
    command.current_dir(cwd).args(args);
    for (key, value) in envs {
        command.env(key, value);
    }

    command
        .spawn()
        .map(|child| ManagedChild { child })
        .wrap_err_with(|| format!("failed to start {label}"))
}

fn path_arg(path: &Path) -> DevResult<&str> {
    path.to_str()
        .ok_or_else(|| color_eyre::eyre::eyre!("path is not valid UTF-8: {}", path.display()))
}

fn cargo() -> OsString {
    env::var_os("CARGO").unwrap_or_else(|| OsString::from("cargo"))
}

fn npm() -> OsString {
    match cfg!(windows) {
        true => OsString::from("npm.cmd"),
        false => OsString::from("npm"),
    }
}

fn resolve_wasm_bindgen(required_version: &str) -> DevResult<OsString> {
    if let Some(configured) = env::var_os("WASM_BINDGEN") {
        if wasm_bindgen_matches(&configured, required_version) {
            return Ok(configured);
        }
        bail!(
            "WASM_BINDGEN does not point to wasm-bindgen {}",
            required_version
        );
    }

    if let Some(executable) = find_on_path("wasm-bindgen") {
        let executable = executable.into_os_string();
        if wasm_bindgen_matches(&executable, required_version) {
            return Ok(executable);
        }
    }

    bail!(
        "wasm-bindgen {} is required for configured WASM public assets; install it with `cargo install wasm-bindgen-cli --version {} --locked` or set WASM_BINDGEN",
        required_version,
        required_version
    );
}

fn wasm_bindgen_matches(executable: &OsString, required_version: &str) -> bool {
    let output = ProcessCommand::new(executable).arg("--version").output();
    let Ok(output) = output else {
        return false;
    };
    let text = String::from_utf8_lossy(&output.stdout);
    output.status.success() && text.contains(required_version)
}

fn find_on_path(name: &str) -> Option<PathBuf> {
    let path = env::var_os("PATH")?;
    for directory in env::split_paths(&path) {
        let candidate = directory.join(name);
        if candidate.is_file() {
            return Some(candidate);
        }
        #[cfg(windows)]
        {
            let candidate = directory.join(format!("{name}.exe"));
            if candidate.is_file() {
                return Some(candidate);
            }
        }
    }
    None
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::net::TcpListener;
    use std::sync::atomic::{AtomicU64, Ordering};

    static TEMP_SEQUENCE: AtomicU64 = AtomicU64::new(0);

    struct TestDirectory(PathBuf);

    impl TestDirectory {
        fn new(label: &str) -> Self {
            let sequence = TEMP_SEQUENCE.fetch_add(1, Ordering::Relaxed);
            let path = env::temp_dir().join(format!(
                "cargo-workspace-{label}-{}-{sequence}",
                std::process::id()
            ));
            fs::create_dir_all(&path).expect("test directory should be created");
            Self(path)
        }

        fn path(&self) -> &Path {
            &self.0
        }
    }

    impl Drop for TestDirectory {
        fn drop(&mut self) {
            let _ = fs::remove_dir_all(&self.0);
        }
    }

    #[test]
    fn project_profile_reuses_the_explicit_identity_by_default() {
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100");

        assert_eq!(profile.app_id(), "example-service");
        assert_eq!(profile.bin_target(), "example-service");
        profile
            .validate("test profile")
            .expect("single-identity profile should be valid");
    }

    #[test]
    fn project_profile_can_isolate_backend_builds() {
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100")
            .with_backend_target_dir("target/example-backend");

        assert_eq!(
            backend_envs(&profile),
            vec![(
                "CARGO_TARGET_DIR".to_string(),
                "target/example-backend".to_string()
            )]
        );
        profile
            .validate("test profile")
            .expect("isolated backend profile should be valid");
    }

    #[test]
    fn wasm_asset_can_use_a_project_relative_target_directory() {
        let asset = ProjectPublicAsset::wasm_bindgen(
            "editor",
            "Example editor",
            "example-editor",
            "example.wasm",
            vec!["public".to_string()],
            "example",
            "0.2.126",
        )
        .with_target_dir("build/web/wasm");

        asset
            .validate("test profile", "example-service")
            .expect("project-relative target directory should be valid");
    }

    #[test]
    fn public_asset_command_parses_optional_absolute_target_directory() {
        let default = AppCli::try_parse_from(["app", "build-public-asset", "--id", "editor"])
            .expect("existing public asset invocation should parse");
        let AppCommand::BuildPublicAsset(default) = default.command else {
            panic!("expected public asset command");
        };
        assert_eq!(default.id, "editor");
        assert!(!default.release);
        assert!(default.target_dir.is_none());

        let directory = TestDirectory::new("public-asset-cli-target");
        let target = directory.path().join("wasm-cache");
        let explicit = AppCli::try_parse_from(vec![
            OsString::from("app"),
            OsString::from("build-public-asset"),
            OsString::from("--id"),
            OsString::from("editor"),
            OsString::from("--release"),
            OsString::from("--target-dir"),
            target.as_os_str().to_os_string(),
        ])
        .expect("explicit public asset target directory should parse");
        let AppCommand::BuildPublicAsset(explicit) = explicit.command else {
            panic!("expected public asset command");
        };
        assert!(explicit.release);
        assert_eq!(explicit.target_dir, Some(target));
    }

    #[test]
    fn public_asset_target_directory_preserves_defaults_and_absolute_override() {
        let directory = TestDirectory::new("public-asset-target-resolution");
        let paths = WorkspacePaths {
            workspace_root: directory.path().to_path_buf(),
            project_root: directory.path().to_path_buf(),
            web_root: directory.path().join("web"),
        };
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100");
        let ProjectPublicAsset::WasmBindgen(mut asset) = ProjectPublicAsset::wasm_bindgen(
            "editor",
            "Example editor",
            "example-editor",
            "example.wasm",
            vec!["public".to_owned()],
            "example",
            "0.2.126",
        );
        assert_eq!(
            resolve_public_asset_target_dir(&profile, &paths, &asset, None).unwrap(),
            paths
                .project_root
                .join("target/example-service-dev-editor-build")
        );
        asset.target_dir = Some("build/web/wasm".to_owned());
        assert_eq!(
            resolve_public_asset_target_dir(&profile, &paths, &asset, None).unwrap(),
            paths.project_root.join("build/web/wasm")
        );
        let explicit = directory.path().join("separate-ssd-cache");
        assert_eq!(
            resolve_public_asset_target_dir(&profile, &paths, &asset, Some(&explicit)).unwrap(),
            explicit
        );
        assert_eq!(asset.target_dir.as_deref(), Some("build/web/wasm"));
        for invalid in [
            PathBuf::new(),
            PathBuf::from("relative/cache"),
            directory.path().join("../cache"),
        ] {
            assert!(
                resolve_public_asset_target_dir(&profile, &paths, &asset, Some(&invalid)).is_err()
            );
        }
    }

    #[test]
    fn missing_backend_artifact_is_a_transient_watch_state() {
        let directory = TestDirectory::new("backend-artifact-transition");
        let artifact = directory.path().join("example-server");

        assert_eq!(
            backend_artifact_stamp_if_present(&artifact)
                .expect("missing artifact should remain a valid watch state"),
            None
        );

        fs::write(&artifact, b"new backend").expect("backend artifact should be written");
        let stamp = backend_artifact_stamp_if_present(&artifact)
            .expect("finished artifact should be readable")
            .expect("finished artifact should be present");
        assert_eq!(stamp.length, 11);
    }

    #[test]
    fn builds_backend_artifacts_before_restarting_the_running_generation() {
        let directory = TestDirectory::new("watchexec-args");
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100")
            .with_bin_target("example-server");
        let paths = WorkspacePaths {
            workspace_root: directory.path().to_path_buf(),
            project_root: directory.path().to_path_buf(),
            web_root: directory.path().join("web"),
        };
        let watch_paths = BackendWatchPaths {
            paths: vec![directory.path().join("src")],
        };

        assert_eq!(
            backend_watchexec_args(&profile, &paths, &watch_paths, false),
            [
                OsString::from("--on-busy-update=queue"),
                OsString::from("--debounce=750ms"),
                OsString::from("--shell=none"),
                OsString::from("--emit-events-to=none"),
                OsString::from("--project-origin"),
                directory.path().as_os_str().to_os_string(),
                OsString::from("--exts"),
                OsString::from("rs,toml,lock,sql"),
                OsString::from("--watch"),
                directory.path().join("src").into_os_string(),
                OsString::from("--"),
                cargo(),
                OsString::from("build"),
                OsString::from("--bin"),
                OsString::from("example-server"),
                OsString::from("--locked"),
            ]
        );

        let release_args = backend_watchexec_args(&profile, &paths, &watch_paths, true);
        assert_eq!(release_args.last(), Some(&OsString::from("--release")));
    }

    #[test]
    fn public_asset_watcher_rebuilds_after_the_initial_public_asset_gate() {
        let directory = TestDirectory::new("public-asset-watcher");
        let paths = WorkspacePaths {
            workspace_root: directory.path().to_path_buf(),
            project_root: directory.path().to_path_buf(),
            web_root: directory.path().join("web"),
        };
        let watch_paths = BackendWatchPaths {
            paths: vec![directory.path().join("src")],
        };
        let asset = ProjectPublicAsset::wasm_bindgen(
            "editor",
            "Example editor",
            "example-editor",
            "example.wasm",
            vec!["public".to_string()],
            "example",
            "0.2.126",
        );

        let args = public_asset_watchexec_args(&paths, &asset, &watch_paths, false)
            .expect("public asset watcher command should resolve");

        // The blocking initial build runs before watch_project. The watcher
        // then performs every later rebuild through the same asset command.
        assert!(!args.contains(&OsString::from("--postpone")));
        assert!(args.contains(&OsString::from("--on-busy-update=queue")));
        assert!(args.contains(&OsString::from("--debounce=750ms")));
        assert!(args.contains(&OsString::from("build-public-asset")));
    }

    #[test]
    fn watch_cli_can_start_the_backend_once_without_a_reload_supervisor() {
        let cli = AppCli::try_parse_from(["project-xtask", "watch", "--no-backend-reload"])
            .expect("watch command should accept the backend reload opt-out");

        let AppCommand::Watch(command) = cli.command else {
            panic!("watch command should preserve its typed owner");
        };
        assert!(command.no_backend_reload);
        assert!(!command.run.release);
    }

    #[test]
    fn optional_asset_switch_is_available_for_watch_serve_and_build() {
        for command_args in [
            ["project-xtask", "watch", "--editor"].as_slice(),
            ["project-xtask", "serve", "--with-optional-assets"].as_slice(),
            ["project-xtask", "build", "--editor"].as_slice(),
        ] {
            let cli = AppCli::try_parse_from(command_args)
                .expect("optional asset switch should be accepted by every run mode");

            let include_optional_assets = match cli.command {
                AppCommand::Watch(command) => command.run.optional_assets.include_optional_assets,
                AppCommand::Serve(command) => command.optional_assets.include_optional_assets,
                AppCommand::Build(command) => command.optional_assets.include_optional_assets,
                AppCommand::BuildPublicAsset(_) => {
                    panic!("internal public asset command is not part of this matrix")
                }
            };
            assert!(include_optional_assets);
        }
    }

    #[test]
    fn optional_public_assets_are_not_active_without_the_explicit_switch() {
        let asset = ProjectPublicAsset::wasm_bindgen(
            "editor",
            "Example editor",
            "example-editor",
            "example.wasm",
            vec!["public".to_string()],
            "example",
            "0.2.126",
        );
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100")
            .with_optional_public_asset(asset);

        let default_profile = activate_optional_public_assets(profile.clone(), false);
        assert!(default_profile.public_assets.is_empty());
        assert_eq!(default_profile.optional_public_assets.len(), 1);

        let enabled_profile = activate_optional_public_assets(profile, true);
        assert_eq!(enabled_profile.public_assets.len(), 1);
        assert!(enabled_profile.optional_public_assets.is_empty());
    }

    #[test]
    fn watches_only_local_packages_reachable_from_the_backend() {
        let directory = TestDirectory::new("cargo-metadata");
        let app_workspace = directory.path().join("app-workspace");
        let app_root = app_workspace.join("app");
        let unused_root = app_workspace.join("unused");
        let shared_workspace = directory.path().join("shared-workspace");
        let shared_root = shared_workspace.join("crates").join("shared");

        for source_root in [
            app_root.join("src"),
            unused_root.join("src"),
            shared_root.join("src"),
        ] {
            fs::create_dir_all(source_root).expect("source directory should be created");
        }
        fs::write(
            app_workspace.join("Cargo.toml"),
            "[workspace]\nmembers = [\"app\", \"unused\"]\nresolver = \"3\"\n",
        )
        .expect("app workspace manifest should be written");
        fs::write(
            shared_workspace.join("Cargo.toml"),
            "[workspace]\nmembers = [\"crates/shared\"]\nresolver = \"3\"\n",
        )
        .expect("shared workspace manifest should be written");
        for (root, name) in [
            (&app_root, "app"),
            (&unused_root, "unused"),
            (&shared_root, "shared"),
        ] {
            fs::write(
                root.join("Cargo.toml"),
                format!("[package]\nname = \"{name}\"\nversion = \"0.1.0\"\n"),
            )
            .expect("package manifest should be written");
        }

        let package = |id: &str, root: &Path, target_name: &str, kind: &str| CargoPackage {
            id: id.to_string(),
            name: id.to_string(),
            source: None,
            manifest_path: root.join("Cargo.toml"),
            targets: vec![CargoTarget {
                kind: vec![kind.to_string()],
                name: target_name.to_string(),
                src_path: root
                    .join("src")
                    .join(if kind == "bin" { "main.rs" } else { "lib.rs" }),
            }],
        };
        let metadata = CargoMetadata {
            packages: vec![
                package("app", &app_root, "example-server", "bin"),
                package("shared", &shared_root, "shared", "lib"),
                package("unused", &unused_root, "unused", "lib"),
                CargoPackage {
                    id: "registry".to_string(),
                    name: "registry".to_string(),
                    source: Some("registry+https://example.invalid".to_string()),
                    manifest_path: directory.path().join("registry").join("Cargo.toml"),
                    targets: Vec::new(),
                },
            ],
            resolve: Some(CargoResolve {
                nodes: vec![
                    CargoResolveNode {
                        id: "app".to_string(),
                        deps: vec![
                            CargoResolveDependency {
                                pkg: "shared".to_string(),
                            },
                            CargoResolveDependency {
                                pkg: "registry".to_string(),
                            },
                        ],
                    },
                    CargoResolveNode {
                        id: "shared".to_string(),
                        deps: Vec::new(),
                    },
                    CargoResolveNode {
                        id: "unused".to_string(),
                        deps: Vec::new(),
                    },
                    CargoResolveNode {
                        id: "registry".to_string(),
                        deps: Vec::new(),
                    },
                ],
            }),
        };

        let watch_paths = backend_watch_paths_from_metadata(&metadata, "example-server")
            .expect("backend watch paths should resolve");
        let public_asset_watch_paths = package_watch_paths_from_metadata(&metadata, "app")
            .expect("public asset watch paths should resolve");

        assert_eq!(watch_paths, public_asset_watch_paths);

        assert!(
            watch_paths
                .paths
                .contains(&app_root.join("src").canonicalize().unwrap())
        );
        assert!(
            watch_paths
                .paths
                .contains(&shared_root.join("src").canonicalize().unwrap())
        );
        assert!(
            !watch_paths
                .paths
                .contains(&unused_root.join("src").canonicalize().unwrap())
        );
        assert!(
            watch_paths
                .paths
                .contains(&app_workspace.join("Cargo.toml").canonicalize().unwrap())
        );
        assert!(
            watch_paths
                .paths
                .contains(&shared_workspace.join("Cargo.toml").canonicalize().unwrap())
        );
        assert!(
            !watch_paths
                .paths
                .contains(&app_root.canonicalize().unwrap())
        );
    }

    #[test]
    fn project_profile_keeps_an_explicit_binary_override() {
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100")
            .with_bin_target("custom-server");

        assert_eq!(profile.app_id(), "example-service");
        assert_eq!(profile.bin_target(), "custom-server");
    }

    #[test]
    fn project_profile_accepts_a_cold_backend_build_timeout() {
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100")
            .with_backend_ready_timeout(Duration::from_secs(900));

        assert_eq!(profile.backend_ready_timeout, Duration::from_secs(900));
        profile
            .validate("test profile")
            .expect("positive readiness timeout should be valid");
    }

    #[test]
    fn project_profile_rejects_a_zero_backend_build_timeout() {
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100")
            .with_backend_ready_timeout(Duration::ZERO);

        let error = profile
            .validate("test profile")
            .expect_err("zero readiness timeout should be rejected");
        assert!(error.to_string().contains("zero backend readiness timeout"));
    }

    #[test]
    fn project_profile_accepts_an_http_backend_readiness_path() {
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100")
            .with_backend_ready_path("/ready");

        assert_eq!(profile.backend_ready_path.as_deref(), Some("/ready"));
        profile
            .validate("test profile")
            .expect("absolute HTTP readiness path should be valid");
    }

    #[test]
    fn project_profile_rejects_an_invalid_http_backend_readiness_path() {
        let profile = ProjectProfile::new("example-service", "127.0.0.1:4100")
            .with_backend_ready_path("ready\r\ninvalid");

        let error = profile
            .validate("test profile")
            .expect_err("invalid HTTP readiness path should be rejected");
        assert!(error.to_string().contains("invalid backend readiness path"));
    }

    #[test]
    fn http_readiness_requires_an_http_response() {
        let listener = TcpListener::bind("127.0.0.1:0").expect("listener should bind");
        let addr = listener
            .local_addr()
            .expect("listener address should resolve");

        probe_backend_http(addr, "/ready")
            .expect_err("a bound socket without a serving backend is not ready");
    }

    #[test]
    fn http_readiness_accepts_a_serving_backend() {
        let listener = TcpListener::bind("127.0.0.1:0").expect("listener should bind");
        let addr = listener
            .local_addr()
            .expect("listener address should resolve");
        let server = thread::spawn(move || {
            let (mut stream, _) = listener.accept().expect("readiness request should connect");
            let mut request = [0_u8; 256];
            let read = stream
                .read(&mut request)
                .expect("readiness request should be readable");
            assert!(read > 0);
            stream
                .write_all(b"HTTP/1.1 204 No Content\r\nContent-Length: 0\r\n\r\n")
                .expect("readiness response should be written");
        });

        probe_backend_http(addr, "/ready").expect("serving backend should be ready");
        server.join().expect("readiness server should finish");
    }

    #[test]
    fn finds_the_owning_cargo_workspace_above_a_member_package() {
        let directory = TestDirectory::new("member");
        let workspace_root = directory.path().join("workspace");
        let package_root = workspace_root.join("crates").join("service");
        let source_root = package_root.join("src");
        fs::create_dir_all(&source_root).expect("member source directory should be created");
        fs::write(
            workspace_root.join("Cargo.toml"),
            "[workspace]\nmembers = [\"crates/service\"]\n",
        )
        .expect("workspace manifest should be written");
        fs::write(
            package_root.join("Cargo.toml"),
            "[package]\nname = \"service\"\nversion = \"0.1.0\"\n",
        )
        .expect("package manifest should be written");

        assert_eq!(
            find_workspace_root(&source_root).expect("workspace should resolve"),
            workspace_root
        );
    }

    #[test]
    fn uses_the_nearest_standalone_package_when_no_workspace_exists() {
        let directory = TestDirectory::new("standalone");
        let package_root = directory.path().join("service");
        let source_root = package_root.join("src");
        fs::create_dir_all(&source_root).expect("package source directory should be created");
        fs::write(
            package_root.join("Cargo.toml"),
            "[package]\nname = \"service\"\nversion = \"0.1.0\"\n",
        )
        .expect("package manifest should be written");

        assert_eq!(
            find_workspace_root(&source_root).expect("package root should resolve"),
            package_root
        );
    }

    #[test]
    fn reports_an_invalid_cargo_manifest() {
        let directory = TestDirectory::new("invalid");
        let package_root = directory.path().join("service");
        fs::create_dir_all(&package_root).expect("package directory should be created");
        fs::write(package_root.join("Cargo.toml"), "[workspace\n")
            .expect("invalid manifest should be written");

        let error = find_workspace_root(&package_root)
            .expect_err("an invalid Cargo manifest must not be ignored");
        assert!(error.to_string().contains("failed to parse Cargo manifest"));
    }
    #[cfg(target_os = "linux")]
    #[test]
    fn managed_child_is_terminated_and_reaped_on_an_error_return() {
        let directory = tempfile::tempdir().unwrap();
        let pid_file = directory.path().join("process.pid");
        let result = (|| -> DevResult<u32> {
            let child = spawn_command(
                "owned test child",
                std::env::current_exe().unwrap().into_os_string(),
                &[
                    "--ignored",
                    "--exact",
                    "docker::tests::process_fixture",
                    "--nocapture",
                ],
                directory.path(),
                &[
                    ("RUNTIME_TEST_PROCESS_CASE".into(), "wait".into()),
                    (
                        "RUNTIME_TEST_PROCESS_PID".into(),
                        pid_file.to_string_lossy().into_owned(),
                    ),
                ],
            )?;
            let pid = child.id();
            let start = Instant::now();
            while !pid_file.exists() {
                assert!(start.elapsed() < Duration::from_secs(10));
                thread::sleep(Duration::from_millis(10));
            }
            Err(color_eyre::eyre::eyre!(
                "setup failed after starting process {pid}"
            ))
        })();
        assert!(result.is_err());
        let pid = fs::read_to_string(pid_file).unwrap();
        assert!(
            !Path::new(&format!("/proc/{}", pid.trim())).exists(),
            "an error return leaked a child process"
        );
    }
}