Auto merge of #7050 - schomatis:fix/fingerprint/dont-update-intermediate-artifacts-mtime, r=Eh2406

fix(fingerpring): do not touch intermediate artifacts

Fixes #6972.

The newly introduced [test](9aa7a4d) is [failing](https://travis-ci.com/rust-lang/cargo/jobs/209849725#L2569-L2580) as discussed in #6972 (comment) (replicating the issue). Removing the `touching of intermediate artifacts` as suggested fixes the issue, but makes the old test `simple_deps_cleaner_does_not_rebuild` fail. The `simple_deps_cleaner_does_not_rebuild` test is not needed anymore so it's removed.

r? @Eh2406

Author: bors

src/cargo/core/compiler/fingerprint.rs

@@ -756,12 +756,7 @@ impl Fingerprint {
     /// dependencies up to this unit as well. This function assumes that the
     /// unit starts out as `FsStatus::Stale` and then it will optionally switch
     /// it to `UpToDate` if it can.
-    fn check_filesystem(
-        &mut self,
-        pkg_root: &Path,
-        target_root: &Path,
-        mtime_on_use: bool,
-    ) -> CargoResult<()> {
+    fn check_filesystem(&mut self, pkg_root: &Path, target_root: &Path) -> CargoResult<()> {
         assert!(!self.fs_status.up_to_date());
 
         let mut mtimes = HashMap::new();
@@ -781,10 +776,6 @@ impl Fingerprint {
                     return Ok(());
                 }
             };
-            if mtime_on_use {
-                let t = FileTime::from_system_time(SystemTime::now());
-                filetime::set_file_times(output, t, t)?;
-            }
             assert!(mtimes.insert(output.clone(), mtime).is_none());
         }
 
@@ -1024,8 +1015,7 @@ fn calculate<'a, 'cfg>(
     // After we built the initial `Fingerprint` be sure to update the
     // `fs_status` field of it.
     let target_root = target_root(cx, unit);
-    let mtime_on_use = cx.bcx.config.cli_unstable().mtime_on_use;
-    fingerprint.check_filesystem(unit.pkg.root(), &target_root, mtime_on_use)?;
+    fingerprint.check_filesystem(unit.pkg.root(), &target_root)?;
 
     let fingerprint = Arc::new(fingerprint);
     cx.fingerprints.insert(*unit, Arc::clone(&fingerprint));

tests/testsuite/freshness.rs

@@ -1170,31 +1170,8 @@ fn changing_rustflags_is_cached() {
         .run();
 }
 
-fn simple_deps_cleaner(mut dir: PathBuf, timestamp: filetime::FileTime) {
-    // Cargo is experimenting with letting outside projects develop some
-    // limited forms of GC for target_dir. This is one of the forms.
-    // Specifically, Cargo is updating the mtime of files in
-    // target/profile/deps each time it uses the file.
-    // So a cleaner can remove files older then a time stamp without
-    // effecting any builds that happened since that time stamp.
-    let mut cleand = false;
-    dir.push("deps");
-    for dep in fs::read_dir(&dir).unwrap() {
-        let dep = dep.unwrap();
-        if filetime::FileTime::from_last_modification_time(&dep.metadata().unwrap()) <= timestamp {
-            fs::remove_file(dep.path()).unwrap();
-            println!("remove: {:?}", dep.path());
-            cleand = true;
-        }
-    }
-    assert!(
-        cleand,
-        "called simple_deps_cleaner, but there was nothing to remove"
-    );
-}
-
 #[cargo_test]
-fn simple_deps_cleaner_does_not_rebuild() {
+fn update_dependency_mtime_does_not_rebuild() {
     let p = project()
         .file(
             "Cargo.toml",
@@ -1212,9 +1189,6 @@ fn simple_deps_cleaner_does_not_rebuild() {
         .file("bar/src/lib.rs", "")
         .build();
 
-    p.cargo("build -Z mtime-on-use")
-        .masquerade_as_nightly_cargo()
-        .run();
     p.cargo("build -Z mtime-on-use")
         .masquerade_as_nightly_cargo()
         .env("RUSTFLAGS", "-C target-cpu=native")
@@ -1225,36 +1199,18 @@ fn simple_deps_cleaner_does_not_rebuild() {
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]",
         )
         .run();
-    if is_coarse_mtime() {
-        sleep_ms(1000);
-    }
-    let timestamp = filetime::FileTime::from_system_time(SystemTime::now());
-    if is_coarse_mtime() {
-        sleep_ms(1000);
-    }
-    // This does not make new files, but it does update the mtime.
-    p.cargo("build -Z mtime-on-use")
+    // This does not make new files, but it does update the mtime of the dependency.
+    p.cargo("build -p bar -Z mtime-on-use")
         .masquerade_as_nightly_cargo()
         .env("RUSTFLAGS", "-C target-cpu=native")
         .with_stderr("[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]")
         .run();
-    simple_deps_cleaner(p.target_debug_dir(), timestamp);
     // This should not recompile!
     p.cargo("build -Z mtime-on-use")
         .masquerade_as_nightly_cargo()
         .env("RUSTFLAGS", "-C target-cpu=native")
         .with_stderr("[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]")
         .run();
-    // But this should be cleaned and so need a rebuild
-    p.cargo("build -Z mtime-on-use")
-        .masquerade_as_nightly_cargo()
-        .with_stderr(
-            "\
-[COMPILING] bar v0.0.1 ([..])
-[COMPILING] foo v0.0.1 ([..])
-[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]",
-        )
-        .run();
 }
 
 fn fingerprint_cleaner(mut dir: PathBuf, timestamp: filetime::FileTime) {