Ignore expansion test if cargo-expand subcommand isn't present

test_suite/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.0.0"
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 edition = "2018"
 publish = false
+build = "build.rs"
 
 [features]
 unstable = ["serde/unstable"]

test_suite/build.rs

@@ -0,0 +1,28 @@
+use std::env;
+use std::path::PathBuf;
+
+#[cfg(not(windows))]
+const CARGO_EXPAND_BIN: &str = "cargo-expand";
+
+#[cfg(windows)]
+const CARGO_EXPAND_BIN: &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() {
+        println!("cargo:rustc-cfg=cargo_expand");
+    }
+}

test_suite/tests/expandtest.rs

@@ -1,5 +1,6 @@
 #[cfg(not(target_os = "emscripten"))]
 #[rustversion::attr(not(nightly), ignore)]
+#[cfg_attr(not(cargo_expand), ignore)]
 #[test]
 fn expandtest() {
     macrotest::expand("tests/expand/**/enum/*.rs");