Function binary_available 

pub fn binary_available(program: &str) -> bool

Check whether a package manager binary is present and runnable.

Answers are cached for the life of the process. Every adapter asks this before it enforces a lockfile, so a monorepo with ten projects on the same manager otherwise pays for ten npm --version process spawns — around half a second each on Windows — to learn the same fact ten times. A run is short-lived, so nothing installed or removed mid-run can be missed for long.