Improve doc & warning for expandtest

tests/expand/README.md

@@ -3,17 +3,15 @@
 Similar to ui tests, but instead of checking the compiler output, this checks
 the code generated by macros.
 
-To run this test, run the following command:
-
-```sh
-cargo test -p expandtest
-```
+See [examples](https://github.com/taiki-e/pin-project/tree/master/examples) for
+descriptions of what the generated code does, and why it needs to be generated.
 
-Or if you want to run all the tests that include this test:
+To run this test, run the following command:
 
 ```sh
-bash scripts/ci.sh
+cargo +nightly test -p expandtest
 ```
 
-See [examples](https://github.com/taiki-e/pin-project/tree/master/examples) for
-descriptions of what the generated code does, and why it needs to be generated.
+Locally, this test updates the files in the `expand` directory if there are
+changes to the generated code. If there are any changes to the files in the
+`expand` directory after running the test, please commit them.

tests/expand/build.rs

@@ -16,8 +16,12 @@ fn main() {
     }
 
     let cargo = &*env::var("CARGO").unwrap_or_else(|_| "cargo".into());
-    if is_ci || has_command(&[cargo, "expand"]) && has_command(&[cargo, "fmt"]) {
+    if has_command(&[cargo, "expand"]) && has_command(&[cargo, "fmt"]) {
         println!("cargo:rustc-cfg=expandtest");
+    } else if is_ci {
+        panic!("expandtest requires rustfmt and cargo-expand")
+    } else {
+        println!("cargo:warning=rustfmt or cargo-expand not found, skipping expandtest",);
     }
 }
 

tests/expand/tests/expandtest.rs

@@ -9,9 +9,8 @@ use std::env;
 #[cfg_attr(not(expandtest), ignore)]
 #[test]
 fn expandtest() {
-    if !cfg!(ci) {
-        env::set_var("MACROTEST", "overwrite");
-    }
+    #[cfg(not(ci))]
+    env::set_var("MACROTEST", "overwrite");
 
     expand("tests/expand/*.rs");
 }