Rely on std::process::Command's path search

test_suite/build.rs

@@ -1,28 +1,22 @@
-use std::env;
-use std::path::PathBuf;
+use std::process::{Command, ExitStatus, Stdio};
 
 #[cfg(not(windows))]
-const CARGO_EXPAND_BIN: &str = "cargo-expand";
+const CARGO_EXPAND: &str = "cargo-expand";
 
 #[cfg(windows)]
-const CARGO_EXPAND_BIN: &str = "cargo-expand.exe";
+const CARGO_EXPAND: &str = "cargo-expand.exe";
 
-/// Scans paths in PATH env variable for a presence of `CARGO_EXPAND_BIN` file.
-fn is_cargo_expand_present() -> bool {
-    if let Ok(var) = env::var("PATH") {
-        for path in var.split(":").map(PathBuf::from) {
-            let cargo_expand_path = path.join(CARGO_EXPAND_BIN);
-            if cargo_expand_path.exists() {
-                return true;
-            }
-        }
-    }
-
-    false
-}
-
-pub fn main() {
-    if is_cargo_expand_present() {
+fn main() {
+    if Command::new(CARGO_EXPAND)
+        .arg("--version")
+        .stdin(Stdio::null())
+        .stdout(Stdio::null())
+        .stderr(Stdio::null())
+        .status()
+        .as_ref()
+        .map(ExitStatus::success)
+        .unwrap_or(false)
+    {
         println!("cargo:rustc-cfg=cargo_expand");
     }
 }