Run expansion tests only if rustfmt is present

test_suite/Cargo.toml

@@ -12,11 +12,14 @@ unstable = ["serde/unstable"]
 [dependencies]
 serde = { path = "../serde" }
 
+[build-dependencies]
+toolchain_find = "0.1"
+
 [dev-dependencies]
 fnv = "1.0"
+macrotest = "=1.0.0"
 rustversion = "1.0"
 serde = { path = "../serde", features = ["rc", "derive"] }
 serde_derive = { path = "../serde_derive", features = ["deserialize_in_place"] }
 serde_test = { path = "../serde_test" }
 trybuild = "1.0"
-macrotest = "=1.0.0"

test_suite/build.rs

@@ -1,13 +1,13 @@
 use std::process::{Command, ExitStatus, Stdio};
 
-#[cfg(not(windows))]
-const CARGO_EXPAND: &str = "cargo-expand";
+fn has_cargo_expand() -> bool {
+    let cargo_expand = if cfg!(windows) {
+        "cargo-expand.exe"
+    } else {
+        "cargo-expand"
+    };
 
-#[cfg(windows)]
-const CARGO_EXPAND: &str = "cargo-expand.exe";
-
-fn main() {
-    if Command::new(CARGO_EXPAND)
+    Command::new(cargo_expand)
         .arg("--version")
         .stdin(Stdio::null())
         .stdout(Stdio::null())
@@ -16,7 +16,14 @@ fn main() {
         .as_ref()
         .map(ExitStatus::success)
         .unwrap_or(false)
-    {
-        println!("cargo:rustc-cfg=cargo_expand");
+}
+
+fn has_rustfmt() -> bool {
+    toolchain_find::find_installed_component("rustfmt").is_some()
+}
+
+fn main() {
+    if has_cargo_expand() && has_rustfmt() {
+        println!("cargo:rustc-cfg=expandtest");
     }
 }

test_suite/tests/expandtest.rs

@@ -1,5 +1,5 @@
 #[cfg_attr(target_os = "emscripten", ignore)]
-#[cfg_attr(not(cargo_expand), ignore)]
+#[cfg_attr(not(expandtest), ignore)]
 #[rustversion::attr(not(nightly), ignore)]
 #[test]
 fn expandtest() {