nits and fix non-deterministic test output

cargo-miri/bin.rs

@@ -38,7 +38,7 @@ enum MiriCommand {
 }
 
 /// The information to run a crate with the given environment.
-#[derive(Serialize, Deserialize, Clone)]
+#[derive(Serialize, Deserialize)]
 struct CrateRunEnv {
     /// The command-line arguments.
     args: Vec<String>,
@@ -52,13 +52,13 @@ struct CrateRunEnv {
 
 impl CrateRunEnv {
     /// Gather all the information we need.
-    fn collect(args: env::Args) -> Self {
+    fn collect(args: env::Args, capture_stdin: bool) -> Self {
         let args = args.collect();
         let env = env::vars_os().collect();
         let current_dir = env::current_dir().unwrap().into_os_string();
 
         let mut stdin = Vec::new();
-        if env::var_os("MIRI_CALLED_FROM_RUSTDOC").is_some() {
+        if capture_stdin {
             std::io::stdin().lock().read_to_end(&mut stdin).expect("cannot read stdin");
         }
 
@@ -669,17 +669,18 @@ fn phase_cargo_rustc(mut args: env::Args) {
     let runnable_crate = !print && is_runnable_crate();
 
     if runnable_crate && target_crate {
+        let inside_rustdoc = env::var_os("MIRI_CALLED_FROM_RUSTDOC").is_some();
         // This is the binary or test crate that we want to interpret under Miri.
         // But we cannot run it here, as cargo invoked us as a compiler -- our stdin and stdout are not
         // like we want them.
         // Instead of compiling, we write JSON into the output file with all the relevant command-line flags
         // and environment variables; this is used when cargo calls us again in the CARGO_TARGET_RUNNER phase.
-        let env = CrateRunEnv::collect(args);
+        let env = CrateRunEnv::collect(args, inside_rustdoc);
 
         // Rustdoc expects us to exit with an error code if the test is marked as `compile_fail`,
         // just creating the JSON file is not enough: we need to detect syntax errors,
         // so we need to run Miri with `MIRI_BE_RUSTC` for a check-only build.
-        if std::env::var_os("MIRI_CALLED_FROM_RUSTDOC").is_some() {
+        if inside_rustdoc {
             let mut cmd = miri();
 
             // Ensure --emit argument for a check-only build is present.

test-cargo-miri/run-test.py

@@ -143,6 +143,7 @@ def test_cargo_miri_test():
 
 os.chdir(os.path.dirname(os.path.realpath(__file__)))
 os.environ["RUST_TEST_NOCAPTURE"] = "0" # this affects test output, so make sure it is not set
+os.environ["RUST_TEST_THREADS"] = "1" # avoid non-deterministic output due to concurrent test runs
 
 target_str = " for target {}".format(os.environ['MIRI_TEST_TARGET']) if 'MIRI_TEST_TARGET' in os.environ else ""
 print(CGREEN + CBOLD + "## Running `cargo miri` tests{}".format(target_str) + CEND)

test-cargo-miri/test.default.stdout.ref

@@ -10,9 +10,9 @@ test result: ok. 6 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out
 
 
 running 3 tests
+test src/lib.rs - make_true (line 2) ... ok
 test src/lib.rs - make_true (line 5) ... ok
 test src/lib.rs - make_true (line 8) ... ok
-test src/lib.rs - make_true (line 2) ... ok
 
 test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME