Auto merge of #11613 - arriven:fix/11083-rerun-if-changed-published-s…

…ources-dir, r=epage

Improve CI caching by skipping mtime checks for paths in $CARGO_HOME

Skip mtime checks for paths pointing into `$CARGO_HOME` to avoid rebuilds when only caching $CARGO_HOME/registry/{index, cache} and $CARGO_HOME/git/db and some of the dependencies have `rerun-if-changed=directory` in their `build.rs`

I considered skipping mtime checking only on `$CARGO_HOME/registry/src` but it looks like other functionality (like downloading a newer version of dependency) is unaffected by this and this way we also cover the same issue with git based dependencies (except the part where `cargo` is forced to re-fetch submodules if `$CARGO_HOME/git/checkouts` is missing) and it is more in line with the discussion in #9455

Fix #11083

Credit `@weihanglo` for the test (I did add a case of checking that dependency update still triggers a rebuild but they are the original author of the rest of the test)

src/cargo/core/compiler/fingerprint.rs

@@ -1785,6 +1785,13 @@ where
 
  for path in paths {
  let path = path.as_ref();
+
+ // Assuming anything in cargo_home is immutable (see also #9455 about marking it readonly)
+ // which avoids rebuilds when CI caches $CARGO_HOME/registry/{index, cache} and
+ // $CARGO_HOME/git/db across runs, keeping the content the same but changing the mtime.
+ if let Ok(true) = home::cargo_home().map(|home| path.starts_with(home)) {
+ continue;
+ }
  let path_mtime = match mtime_cache.entry(path.to_path_buf()) {
  Entry::Occupied(o) => *o.get(),
  Entry::Vacant(v) => {

tests/testsuite/build_script.rs

@@ -1,6 +1,7 @@
 //! Tests for build.rs scripts.
 
 use cargo_test_support::compare::assert_match_exact;
+use cargo_test_support::install::cargo_home;
 use cargo_test_support::paths::CargoPathExt;
 use cargo_test_support::registry::Package;
 use cargo_test_support::tools;
@@ -4803,6 +4804,84 @@ fn rerun_if_directory() {
  fresh();
 }
 
+#[cargo_test]
+fn rerun_if_published_directory() {
+ // build script of a dependency contains a `rerun-if-changed` pointing to a directory
+ Package::new("mylib-sys", "1.0.0")
+ .file("mylib/balrog.c", "")
+ .file("src/lib.rs", "")
+ .file(
+ "build.rs",
+ r#"
+ fn main() {
+ // Changing to mylib/balrog.c will not trigger a rebuild
+ println!("cargo:rerun-if-changed=mylib");
+ }
+ "#,
+ )
+ .publish();
+
+ let p = project()
+ .file(
+ "Cargo.toml",
+ r#"
+ [package]
+ name = "foo"
+ version = "0.0.1"
+
+ [dependencies]
+ mylib-sys = "1.0.0"
+ "#,
+ )
+ .file("src/main.rs", "fn main() {}")
+ .build();
+
+ p.cargo("check").run();
+
+ // Delete regitry src to make directories being recreated with the latest timestamp.
+ cargo_home().join("registry/src").rm_rf();
+
+ p.cargo("check --verbose")
+ .with_stderr(
+ "\
+[FRESH] mylib-sys v1.0.0
+[FRESH] foo v0.0.1 ([CWD])
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+ )
+ .run();
+
+ // Upgrade of a package should still trigger a rebuild
+ Package::new("mylib-sys", "1.0.1")
+ .file("mylib/balrog.c", "")
+ .file("mylib/balrog.h", "")
+ .file("src/lib.rs", "")
+ .file(
+ "build.rs",
+ r#"
+ fn main() {
+ println!("cargo:rerun-if-changed=mylib");
+ }
+ "#,
+ )
+ .publish();
+ p.cargo("update").run();
+ p.cargo("fetch").run();
+
+ p.cargo("check -v")
+ .with_stderr(format!(
+ "\
+[COMPILING] mylib-sys [..]
+[RUNNING] `rustc --crate-name build_script_build [..]
+[RUNNING] `[..]build-script-build[..]`
+[RUNNING] `rustc --crate-name mylib_sys [..]
+[CHECKING] foo [..]
+[RUNNING] `rustc --crate-name foo [..]
+[FINISHED] [..]",
+ ))
+ .run();
+}
+
 #[cargo_test]
 fn test_with_dep_metadata() {
  let p = project()