[hermes] Isolate shadow crate from other artifacts

Previously, we stored the shadow crate in `target/hermes_shadow_<hash>`.
Now we store it in `target/hermes/<hash>/shadow`. This allows us to
store other build artifacts in `target/hermes/<hash>` but outside of
`/shadow` to avoid polluting the shadow copy.

gherrit-pr-id: G7f8abd90b628d02a6fdc01985535eef50509312e

Author: joshlf

tools/hermes/src/resolve.rs

@@ -102,10 +102,17 @@ impl TryFrom<&TargetKind> for HermesTargetKind {
 pub struct Roots {
     pub workspace: PathBuf,
     pub cargo_target_dir: PathBuf,
-    pub shadow_root: PathBuf,
+    // E.g., `target/hermes/<hash>`.
+    hermes_run_root: PathBuf,
     pub roots: Vec<(PackageName, HermesTargetKind, PathBuf)>,
 }
 
+impl Roots {
+    pub fn shadow_root(&self) -> PathBuf {
+        self.hermes_run_root.join("shadow")
+    }
+}
+
 /// Resolves all verification roots.
 ///
 /// Each entry represents a distinct compilation artifact to be verified.
@@ -129,7 +136,7 @@ pub fn resolve_roots(args: &Args) -> Result<Roots> {
     let mut roots = Roots {
         workspace: metadata.workspace_root.as_std_path().to_owned(),
         cargo_target_dir: metadata.target_directory.as_std_path().to_owned(),
-        shadow_root: resolve_shadow_path(&metadata),
+        hermes_run_root: resolve_run_root(&metadata),
         roots: Vec::new(),
     };
 
@@ -155,15 +162,16 @@ pub fn resolve_roots(args: &Args) -> Result<Roots> {
     Ok(roots)
 }
 
-fn resolve_shadow_path(metadata: &Metadata) -> PathBuf {
-    log::trace!("resolve_shadow_path");
+fn resolve_run_root(metadata: &Metadata) -> PathBuf {
+    log::trace!("resolve_run_root");
     log::debug!("workspace_root: {:?}", metadata.workspace_root.as_std_path());
     // NOTE: Automatically handles `CARGO_TARGET_DIR` env var.
     let target_dir = metadata.target_directory.as_std_path();
+    let hermes_global = target_dir.join("hermes");
 
     // Used by integration tests to ensure deterministic shadow dir names.
     if let Ok(name) = std::env::var("HERMES_TEST_SHADOW_NAME") {
-        return target_dir.join(name);
+        return hermes_global.join(name);
     }
 
     // Hash the path to the workspace root to avoid collisions between different
@@ -175,7 +183,7 @@ fn resolve_shadow_path(metadata: &Metadata) -> PathBuf {
         hasher.finish()
     };
 
-    target_dir.join(format!("hermes_shadow_{workspace_root_hash}"))
+    hermes_global.join(format!("{workspace_root_hash:x}"))
 }
 
 /// Resolves which packages to process based on workspace flags and CWD.

tools/hermes/src/shadow.rs

@@ -18,10 +18,11 @@ use crate::{parse, resolve::Roots, transform};
 /// 2. Creates symlinks for the remaining skeleton.
 pub fn build_shadow_crate(roots: &Roots) -> Result<()> {
     log::trace!("build_shadow_crate({:?})", roots);
-    if roots.shadow_root.exists() {
-        fs::remove_dir_all(&roots.shadow_root).context("Failed to clear shadow root")?;
+    let shadow_root = roots.shadow_root();
+    if shadow_root.exists() {
+        fs::remove_dir_all(&shadow_root).context("Failed to clear shadow root")?;
     }
-    fs::create_dir_all(&roots.shadow_root).context("Failed to create shadow root")?;
+    fs::create_dir_all(&shadow_root).context("Failed to create shadow root")?;
 
     let visited_paths = DashSet::new();
     let (err_tx, err_rx) = std::sync::mpsc::channel();
@@ -62,12 +63,7 @@ pub fn build_shadow_crate(roots: &Roots) -> Result<()> {
 
     let skip_paths: HashSet<PathBuf> = visited_paths.into_iter().collect();
 
-    create_symlink_skeleton(
-        &roots.workspace,
-        &roots.shadow_root,
-        &roots.cargo_target_dir,
-        &skip_paths,
-    )?;
+    create_symlink_skeleton(&roots.workspace, &shadow_root, &roots.cargo_target_dir, &skip_paths)?;
 
     Ok(())
 }
@@ -99,7 +95,7 @@ fn process_file_recursive<'a>(
             return;
         }
     };
-    let dest_path = config.shadow_root.join(relative_path);
+    let dest_path = config.shadow_root().join(relative_path);
 
     let result = (|| -> Result<Vec<PathBuf>> {
         if let Some(parent) = dest_path.parent() {

tools/hermes/tests/integration.rs

@@ -20,7 +20,7 @@ fn run_integration_test(path: &Path) -> datatest_stable::Result<()> {
     let mut cmd = assert_cmd::cargo_bin_cmd!("hermes");
     cmd.env("CARGO_TARGET_DIR", sandbox_root.join("target"))
         .env_remove("RUSTFLAGS")
-        .env("HERMES_TEST_SHADOW_NAME", "hermes_shadow");
+        .env("HERMES_TEST_SHADOW_NAME", "hermes_test_target");
 
     // Tests can specify the cwd to invoke from.
     let cwd_file = test_case_root.join("cwd.txt");
@@ -64,7 +64,7 @@ fn run_integration_test(path: &Path) -> datatest_stable::Result<()> {
     }
 
     // Tests can specify the expected shadow crate content.
-    let actual_shadow = sandbox_root.join("target/hermes_shadow");
+    let actual_shadow = sandbox_root.join("target/hermes/hermes_test_target/shadow");
     let expected_shadow = test_case_root.join("expected");
 
     if expected_shadow.exists() {