jdx/mise · error · eyre::Report

brew-cask: binary $APPDIR target '{target_name}' must stay b

Error message

brew-cask: binary $APPDIR target '{target_name}' must stay below Applications

What it means

binary_target_path supports the $APPDIR/ placeholder for binaries that must live inside the Applications tree. After stripping "$APPDIR/", the remainder must be non-empty and consist only of Component::Normal entries — no '..', no '.', no embedded absolute segments. This bail rejects placeholders that would escape the Applications subtree.

Source

Thrown at src/system/packages/brew/cask.rs:6140

    roots
        .iter()
        .map(|root| root.display().to_string())
        .collect::<Vec<_>>()
        .join(" or ")
}

fn binary_target_path(target_name: &str, appdir: &Path) -> Result<PathBuf> {
    if target_name.contains('\0') {
        bail!("brew-cask: binary target contains NUL");
    }
    if let Some(relative) = target_name.strip_prefix("$APPDIR/") {
        let relative = Path::new(relative);
        if relative.components().next().is_none()
            || relative
                .components()
                .any(|component| !matches!(component, Component::Normal(_)))
        {
            bail!("brew-cask: binary $APPDIR target '{target_name}' must stay below Applications");
        }
        if !allowed_appdir_roots()?.iter().any(|root| root == appdir) {
            bail!("brew-cask: invalid appdir '{}'", appdir.display());
        }
        return Ok(appdir.join(relative));
    }
    if target_name.contains("$APPDIR") {
        bail!("brew-cask: $APPDIR must prefix a binary target");
    }
    let prefix = prefix::prefix();
    let prefix_str = prefix.to_string_lossy();
    let target_name = target_name.replace("$HOMEBREW_PREFIX", prefix_str.as_ref());
    let path = PathBuf::from(&target_name);
    let target = if path.is_absolute() {
        path
    } else if target_name.contains('/') {
        prefix.join(path)
    } else {

View on GitHub (pinned to 9dcfcaa0dc)

Solutions

Use a clean single relative remainder: "$APPDIR/Foo.app/Contents/MacOS/tool"
Avoid '..' and '.' segments after $APPDIR/
If the target comes from a tap, report/fix the artifact stanza upstream

Example fix

// before (cask binary target)
"target": "$APPDIR/../Foo.app/Contents/MacOS/tool"
// after
"target": "$APPDIR/Foo.app/Contents/MacOS/tool"

Defensive patterns

Strategy: type-guard

Type guard

use std::path::{Component, Path};
fn is_valid_appdir_binary_target(name: &str) -> bool {
    match name.strip_prefix("$APPDIR/") {
        Some(rest) => {
            let rel = Path::new(rest);
            rel.components().next().is_some()
                && rel.components().all(|c| matches!(c, Component::Normal(_)))
        }
        None => true, // non-$APPDIR targets follow other rules
    }
}

Try / catch

match binary_target_path(name, &appdir) {
    Ok(p) => p,
    Err(e) if e.to_string().contains("must stay below Applications") => {
        warn!("skipping unsafe $APPDIR binary target: {name}");
        continue;
    }
    Err(e) => Err(e),
}

Prevention

Keep $APPDIR targets a single clean relative remainder with no '..', '.', or empty segments
Use $APPDIR only as a leading prefix followed by exactly one '/'

When it happens

Trigger: A binary target of exactly "$APPDIR/" (empty remainder), or "$APPDIR/../Foo.app", or any $APPDIR-relative target whose component list contains a non-Normal component.

Common situations: Hand-written casks using $APPDIR incorrectly; malicious or malformed taps; copy-paste errors like "$APPDIR//tool" or "$APPDIR/./tool".

Related errors

AI-assisted analysis of jdx/mise@9dcfcaa0dc (2026-08-17). Data as JSON: /api/errors/706d53bd75e6f42e. Report an issue: GitHub.