Auto merge of #6720 - ehuss:build-script-fingerprint, r=alexcrichton

Include build script execution in the fingerprint.

This adds information about the execution of a build script to the fingerprint. Previously, no information was included, and cargo relied on dirty propagation in `JobQueue` to trigger recompiles. However, if two separate targets are built via separate commands (such as `cargo build` then `cargo test`), the second command did not know that the build script was updated, and thus was incorrectly treated as "fresh".

This works by including the timestamp of the last time the build script was ran in the fingerprint. For overridden build scripts, it includes the replaced output.

Fixes #4979

src/cargo/core/compiler/context/compilation_files.rs

@@ -186,20 +186,29 @@ impl<'a, 'cfg: 'a> CompilationFiles<'a, 'cfg> {
         self.layout(unit.kind).fingerprint().join(dir)
     }
 
-    /// Returns the appropriate directory layout for either a plugin or not.
+    /// Returns the directory where a compiled build script is stored.
+    /// `/path/to/target/{debug,release}/build/PKG-HASH`
     pub fn build_script_dir(&self, unit: &Unit<'a>) -> PathBuf {
         assert!(unit.target.is_custom_build());
         assert!(!unit.mode.is_run_custom_build());
         let dir = self.pkg_dir(unit);
         self.layout(Kind::Host).build().join(dir)
     }
 
-    /// Returns the appropriate directory layout for either a plugin or not.
-    pub fn build_script_out_dir(&self, unit: &Unit<'a>) -> PathBuf {
+    /// Returns the directory where information about running a build script
+    /// is stored.
+    /// `/path/to/target/{debug,release}/build/PKG-HASH`
+    pub fn build_script_run_dir(&self, unit: &Unit<'a>) -> PathBuf {
         assert!(unit.target.is_custom_build());
         assert!(unit.mode.is_run_custom_build());
         let dir = self.pkg_dir(unit);
-        self.layout(unit.kind).build().join(dir).join("out")
+        self.layout(unit.kind).build().join(dir)
+    }
+
+    /// Returns the "OUT_DIR" directory for running a build script.
+    /// `/path/to/target/{debug,release}/build/PKG-HASH/out`
+    pub fn build_script_out_dir(&self, unit: &Unit<'a>) -> PathBuf {
+        self.build_script_run_dir(unit).join("out")
     }
 
     /// Returns the file stem for a given target/profile combo (with metadata).

src/cargo/core/compiler/custom_build.rs

@@ -132,6 +132,7 @@ fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>) -> CargoRes
         .expect("running a script not depending on an actual script");
     let script_dir = cx.files().build_script_dir(build_script_unit);
     let script_out_dir = cx.files().build_script_out_dir(unit);
+    let script_run_dir = cx.files().build_script_run_dir(unit);
     let build_plan = bcx.build_config.build_plan;
     let invocation_name = unit.buildkey();
 
@@ -241,13 +242,9 @@ fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>) -> CargoRes
     let pkg_name = unit.pkg.to_string();
     let build_state = Arc::clone(&cx.build_state);
     let id = unit.pkg.package_id();
-    let (output_file, err_file, root_output_file) = {
-        let build_output_parent = script_out_dir.parent().unwrap();
-        let output_file = build_output_parent.join("output");
-        let err_file = build_output_parent.join("stderr");
-        let root_output_file = build_output_parent.join("root-output");
-        (output_file, err_file, root_output_file)
-    };
+    let output_file = script_run_dir.join("output");
+    let err_file = script_run_dir.join("stderr");
+    let root_output_file = script_run_dir.join("root-output");
     let host_target_root = cx.files().target_root().to_path_buf();
     let all = (
         id,
@@ -332,7 +329,7 @@ fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>) -> CargoRes
             state.build_plan(invocation_name, cmd.clone(), Arc::new(Vec::new()));
         } else {
             state.running(&cmd);
-            let timestamp = paths::get_current_filesystem_time(&output_file)?;
+            let timestamp = paths::set_invocation_time(&script_run_dir)?;
             let output = if extra_verbose {
                 let prefix = format!("[{} {}] ", id.name(), id.version());
                 state.capture_output(&cmd, Some(prefix), true)

src/cargo/core/compiler/fingerprint.rs

@@ -455,13 +455,12 @@ fn calculate<'a, 'cfg>(
 
     // Next, recursively calculate the fingerprint for all of our dependencies.
     //
-    // Skip the fingerprints of build scripts as they may not always be
-    // available and the dirtiness propagation for modification is tracked
-    // elsewhere. Also skip fingerprints of binaries because they don't actually
-    // induce a recompile, they're just dependencies in the sense that they need
-    // to be built.
-    let deps = cx.dep_targets(unit);
-    let deps = deps
+    // Skip the fingerprints of build scripts, they are included below in the
+    // `local` vec. Also skip fingerprints of binaries because they don't
+    // actually induce a recompile, they're just dependencies in the sense
+    // that they need to be built.
+    let mut deps = cx
+        .dep_targets(unit)
         .iter()
         .filter(|u| !u.target.is_custom_build() && !u.target.is_bin())
         .map(|dep| {
@@ -475,8 +474,9 @@ fn calculate<'a, 'cfg>(
             })
         })
         .collect::<CargoResult<Vec<_>>>()?;
+    deps.sort_by(|a, b| a.pkg_id.cmp(&b.pkg_id));
 
-    // And finally, calculate what our own local fingerprint is
+    // And finally, calculate what our own local fingerprint is.
     let local = if use_dep_info(unit) {
         let dep_info = dep_info_loc(cx, unit);
         let mtime = dep_info_mtime_if_fresh(unit.pkg, &dep_info)?;
@@ -485,8 +485,32 @@ fn calculate<'a, 'cfg>(
         let fingerprint = pkg_fingerprint(&cx.bcx, unit.pkg)?;
         LocalFingerprint::Precalculated(fingerprint)
     };
-    let mut deps = deps;
-    deps.sort_by(|a, b| a.pkg_id.cmp(&b.pkg_id));
+    let mut local = vec![local];
+    // Include fingerprint for any build scripts this unit requires.
+    local.extend(
+        cx.dep_targets(unit)
+            .iter()
+            .filter(|u| u.mode.is_run_custom_build())
+            .map(|dep| {
+                // If the build script is overridden, use the override info as
+                // the override. Otherwise, use the last invocation time of
+                // the build script. If the build script re-runs during this
+                // run, dirty propagation within the JobQueue will ensure that
+                // this gets invalidated. This is only here to catch the
+                // situation when cargo is run a second time for another
+                // target that wasn't built previously (such as `cargo build`
+                // then `cargo test`).
+                build_script_override_fingerprint(cx, unit).unwrap_or_else(|| {
+                    let ts_path = cx
+                        .files()
+                        .build_script_run_dir(dep)
+                        .join("invoked.timestamp");
+                    let ts_path_mtime = paths::mtime(&ts_path).ok();
+                    LocalFingerprint::mtime(cx.files().target_root(), ts_path_mtime, &ts_path)
+                })
+            }),
+    );
+
     let extra_flags = if unit.mode.is_doc() {
         bcx.rustdocflags_args(unit)?
     } else {
@@ -502,7 +526,7 @@ fn calculate<'a, 'cfg>(
         path: util::hash_u64(&super::path_args(&cx.bcx, unit).0),
         features: format!("{:?}", bcx.resolve.features_sorted(unit.pkg.package_id())),
         deps,
-        local: vec![local],
+        local,
         memoized_hash: Mutex::new(None),
         edition: unit.target.edition(),
         rustflags: extra_flags,
@@ -595,19 +619,13 @@ fn build_script_local_fingerprints<'a, 'cfg>(
     cx: &mut Context<'a, 'cfg>,
     unit: &Unit<'a>,
 ) -> CargoResult<(Vec<LocalFingerprint>, Option<PathBuf>)> {
-    let state = cx.build_state.outputs.lock().unwrap();
     // First up, if this build script is entirely overridden, then we just
     // return the hash of what we overrode it with.
-    //
-    // Note that the `None` here means that we don't want to update the local
-    // fingerprint afterwards because this is all just overridden.
-    if let Some(output) = state.get(&(unit.pkg.package_id(), unit.kind)) {
+    if let Some(fingerprint) = build_script_override_fingerprint(cx, unit) {
         debug!("override local fingerprints deps");
-        let s = format!(
-            "overridden build state with hash: {}",
-            util::hash_u64(output)
-        );
-        return Ok((vec![LocalFingerprint::Precalculated(s)], None));
+        // Note that the `None` here means that we don't want to update the local
+        // fingerprint afterwards because this is all just overridden.
+        return Ok((vec![fingerprint], None));
     }
 
     // Next up we look at the previously listed dependencies for the build
@@ -633,6 +651,24 @@ fn build_script_local_fingerprints<'a, 'cfg>(
     ))
 }
 
+/// Create a local fingerprint for an overridden build script.
+/// Returns None if it is not overridden.
+fn build_script_override_fingerprint<'a, 'cfg>(
+    cx: &mut Context<'a, 'cfg>,
+    unit: &Unit<'a>,
+) -> Option<LocalFingerprint> {
+    let state = cx.build_state.outputs.lock().unwrap();
+    state
+        .get(&(unit.pkg.package_id(), unit.kind))
+        .map(|output| {
+            let s = format!(
+                "overridden build state with hash: {}",
+                util::hash_u64(output)
+            );
+            LocalFingerprint::Precalculated(s)
+        })
+}
+
 fn local_fingerprints_deps(
     deps: &BuildDeps,
     target_root: &Path,

src/cargo/core/compiler/mod.rs

@@ -239,6 +239,7 @@ fn rustc<'a, 'cfg>(
         .get_cwd()
         .unwrap_or_else(|| cx.bcx.config.cwd())
         .to_path_buf();
+    let fingerprint_dir = cx.files().fingerprint_dir(unit);
 
     return Ok(Work::new(move |state| {
         // Only at runtime have we discovered what the extra -L and -l
@@ -289,7 +290,7 @@ fn rustc<'a, 'cfg>(
         }
 
         state.running(&rustc);
-        let timestamp = paths::get_current_filesystem_time(&dep_info_loc)?;
+        let timestamp = paths::set_invocation_time(&fingerprint_dir)?;
         if json_messages {
             exec.exec_json(
                 rustc,

src/cargo/util/paths.rs

@@ -187,16 +187,17 @@ pub fn mtime(path: &Path) -> CargoResult<FileTime> {
     Ok(FileTime::from_last_modification_time(&meta))
 }
 
-/// get `FileTime::from_system_time(SystemTime::now());` using the exact clock that this file system is using.
-pub fn get_current_filesystem_time(path: &Path) -> CargoResult<FileTime> {
+/// Record the current time on the filesystem (using the filesystem's clock)
+/// using a file at the given directory. Returns the current time.
+pub fn set_invocation_time(path: &Path) -> CargoResult<FileTime> {
     // note that if `FileTime::from_system_time(SystemTime::now());` is determined to be sufficient,
     // then this can be removed.
-    let timestamp = path.with_file_name("invoked.timestamp");
+    let timestamp = path.join("invoked.timestamp");
     write(
         &timestamp,
         b"This file has an mtime of when this was started.",
     )?;
-    Ok(mtime(&timestamp)?)
+    mtime(&timestamp)
 }
 
 #[cfg(unix)]

tests/testsuite/freshness.rs

@@ -1616,3 +1616,91 @@ fn rebuild_on_mid_build_file_modification() {
 
     t.join().ok().unwrap();
 }
+
+#[test]
+fn dirty_both_lib_and_test() {
+    // This tests that all artifacts that depend on the results of a build
+    // script will get rebuilt when the build script reruns, even for separate
+    // commands. It does the following:
+    //
+    // 1. Project "foo" has a build script which will compile a small
+    //    staticlib to link against. Normally this would use the `cc` crate,
+    //    but here we just use rustc to avoid the `cc` dependency.
+    // 2. Build the library.
+    // 3. Build the unit test. The staticlib intentionally has a bad value.
+    // 4. Rewrite the staticlib with the correct value.
+    // 5. Build the library again.
+    // 6. Build the unit test. This should recompile.
+
+    let slib = |n| {
+        format!(
+            r#"
+            #[no_mangle]
+            pub extern "C" fn doit() -> i32 {{
+                return {};
+            }}
+        "#,
+            n
+        )
+    };
+
+    let p = project()
+        .file(
+            "src/lib.rs",
+            r#"
+            extern "C" {
+                fn doit() -> i32;
+            }
+
+            #[test]
+            fn t1() {
+                assert_eq!(unsafe { doit() }, 1, "doit assert failure");
+            }
+        "#,
+        )
+        .file(
+            "build.rs",
+            r#"
+            use std::env;
+            use std::path::PathBuf;
+            use std::process::Command;
+
+            fn main() {
+                let rustc = env::var_os("RUSTC").unwrap();
+                let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
+                assert!(
+                    Command::new(rustc)
+                        .args(&[
+                            "--crate-type=staticlib",
+                            "--out-dir",
+                            out_dir.to_str().unwrap(),
+                            "slib.rs"
+                        ])
+                        .status()
+                        .unwrap()
+                        .success(),
+                    "slib build failed"
+                );
+                println!("cargo:rustc-link-lib=slib");
+                println!("cargo:rustc-link-search={}", out_dir.display());
+            }
+        "#,
+        )
+        .file("slib.rs", &slib(2))
+        .build();
+
+    p.cargo("build").run();
+
+    // 2 != 1
+    p.cargo("test --lib")
+        .with_status(101)
+        .with_stdout_contains("[..]doit assert failure[..]")
+        .run();
+
+    // Fix the mistake.
+    p.change_file("slib.rs", &slib(1));
+
+    p.cargo("build").run();
+    // This should recompile with the new static lib, and the test should pass.
+    p.cargo("test --lib").run();
+}