Auto merge of #8819 - EmbarkStudios:target-root-path, r=ehuss

Make host_root return host.root(), not host.dest()

Also create host_dest function to let other callsites retain their old functionality. Fixes #8817, verified it works on the original problem reported in the `rust-gpu` repo.

I did two things here:

1) Rename `host_root` (which returns `self.host.dest()`) to be `host_dest`. This has three callsites. I did this to make it more clear that it returns dest, not root.
2) For the callsite that's relevant in #8817, I created a "new" `host_root` function (that returns `self.host.root()`). This means that the callsite that this PR is actually fixing doesn't show up in this diff :/ - but I thought it was more clear this way.

(Also copied the example path docs over from `layout.rs` to hopefully avoid this mistake again in the future)

I tried to look into if the other two callsites should actually be calling `host.root()` instead of `dest`, because I imagine the same mistake could have been made again, but it quickly grew out of my understanding (this is my first time in the cargo codebase). Feel free to let me know if they should also call `host.root()` too, and I can update them.

Thanks! (oh gosh I have no idea what I'm doing, I hope this is right)

r? `@alexcrichton`

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

@@ -207,11 +207,16 @@ impl<'a, 'cfg: 'a> CompilationFiles<'a, 'cfg> {
         }
     }
 
-    /// Returns the root of the build output tree for the host
-    pub fn host_root(&self) -> &Path {
+    /// Returns the final artifact path for the host (`/…/target/debug`)
+    pub fn host_dest(&self) -> &Path {
         self.host.dest()
     }
 
+    /// Returns the root of the build output tree for the host (`/…/target`)
+    pub fn host_root(&self) -> &Path {
+        self.host.root()
+    }
+
     /// Returns the host `deps` directory path.
     pub fn host_deps(&self) -> &Path {
         self.host.deps()

src/cargo/core/compiler/custom_build.rs

@@ -272,7 +272,7 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
     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().host_root().to_path_buf();
+    let host_target_root = cx.files().host_dest().to_path_buf();
     let all = (
         id,
         pkg_name.clone(),

src/cargo/core/compiler/mod.rs

@@ -217,7 +217,7 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
     exec.init(cx, unit);
     let exec = exec.clone();
 
-    let root_output = cx.files().host_root().to_path_buf();
+    let root_output = cx.files().host_dest().to_path_buf();
     let target_dir = cx.bcx.ws.target_dir().into_path_unlocked();
     let pkg_root = unit.pkg.root().to_path_buf();
     let cwd = rustc

tests/testsuite/dep_info.rs

@@ -176,6 +176,42 @@ fn build_dep_info_dylib() {
     assert!(p.example_lib("ex", "dylib").with_extension("d").is_file());
 }
 
+#[cargo_test]
+fn dep_path_inside_target_has_correct_path() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("a"))
+        .file("target/debug/blah", "")
+        .file(
+            "src/main.rs",
+            r#"
+                fn main() {
+                    let x = include_bytes!(concat!(env!("CARGO_MANIFEST_DIR"), "/target/debug/blah"));
+                }
+            "#,
+        )
+        .build();
+
+    p.cargo("build").run();
+
+    let depinfo_path = &p.bin("a").with_extension("d");
+
+    assert!(depinfo_path.is_file(), "{:?}", depinfo_path);
+
+    let depinfo = p.read_file(depinfo_path.to_str().unwrap());
+
+    let bin_path = p.bin("a");
+    let target_debug_blah = Path::new("target").join("debug").join("blah");
+    if !depinfo.lines().any(|line| {
+        line.starts_with(&format!("{}:", bin_path.display()))
+            && line.contains(target_debug_blah.to_str().unwrap())
+    }) {
+        panic!(
+            "Could not find {:?}: {:?} in {:?}",
+            bin_path, target_debug_blah, depinfo_path
+        );
+    }
+}
+
 #[cargo_test]
 fn no_rewrite_if_no_change() {
     let p = project().file("src/lib.rs", "").build();