Improve warning for expandtest

tests/expand/Cargo.toml

@@ -8,3 +8,4 @@ publish = false
 [dev-dependencies]
 pin-project-lite = { path = "../.." }
 macrotest = "1.0.6"
+rustversion = "1"

tests/expand/build.rs

@@ -10,14 +10,9 @@ fn main() {
         return;
     }
 
-    let is_ci = env::var_os("CI").is_some();
-    if is_ci {
-        println!("cargo:rustc-cfg=ci");
-    }
-
     let cargo = &*env::var("CARGO").unwrap_or_else(|_| "cargo".into());
-    if is_ci || has_command(&[cargo, "expand"]) && has_command(&[cargo, "fmt"]) {
-        println!("cargo:rustc-cfg=expandtest");
+    if !has_command(&[cargo, "expand"]) || !has_command(&[cargo, "fmt"]) {
+        println!("cargo:warning=rustfmt or cargo-expand not found, skipping expandtest");
     }
 }
 

tests/expand/tests/expandtest.rs

@@ -1,17 +1,39 @@
 #![warn(rust_2018_idioms, single_use_lifetimes)]
 
-#[cfg(not(ci))]
-use macrotest::expand;
-#[cfg(ci)]
-use macrotest::expand_without_refresh as expand;
-use std::env;
+use std::{
+    env,
+    process::{Command, ExitStatus, Stdio},
+};
 
-#[cfg_attr(not(expandtest), ignore)]
+#[rustversion::attr(not(nightly), ignore)]
 #[test]
 fn expandtest() {
-    if !cfg!(ci) {
+    let is_ci = env::var_os("CI").is_some();
+    let cargo = &*env::var("CARGO").unwrap_or_else(|_| "cargo".into());
+    if !has_command(&[cargo, "expand"]) || !has_command(&[cargo, "fmt"]) {
+        if is_ci {
+            panic!("expandtest requires rustfmt and cargo-expand")
+        }
+        return;
+    }
+
+    if is_ci {
+        macrotest::expand_without_refresh("tests/expand/*.rs");
+    } else {
         env::set_var("MACROTEST", "overwrite");
+        macrotest::expand("tests/expand/*.rs");
     }
+}
 
-    expand("tests/expand/*.rs");
+fn has_command(command: &[&str]) -> bool {
+    Command::new(command[0])
+        .args(&command[1..])
+        .arg("--version")
+        .stdin(Stdio::null())
+        .stdout(Stdio::null())
+        .stderr(Stdio::null())
+        .status()
+        .as_ref()
+        .map(ExitStatus::success)
+        .unwrap_or(false)
 }