Canonicalize path_args src

src/cargo/core/compiler/mod.rs

@@ -688,6 +688,7 @@ fn path_args(bcx: &BuildContext<'_, '_>, unit: &Unit<'_>) -> (PathBuf, PathBuf)
         TargetSourcePath::Metabuild => unit.pkg.manifest().metabuild_path(bcx.ws.target_dir()),
     };
     assert!(src.is_absolute());
+    let src = canonicalize_path_arg(&src).unwrap_or(src);
     if unit.pkg.package_id().source_id().is_path() {
         if let Ok(path) = src.strip_prefix(ws_root) {
             return (path.to_path_buf(), ws_root.to_path_buf());
@@ -696,6 +697,19 @@ fn path_args(bcx: &BuildContext<'_, '_>, unit: &Unit<'_>) -> (PathBuf, PathBuf)
     (src, unit.pkg.root().to_path_buf())
 }
 
+#[cfg(windows)]
+// On Windows cargo cannot read back the canonicalized paths. The paths are
+// canonicalized to resolve symlinks, which aren't as ordinary on Windows as
+// they are on other platforms, so we simply skip this.
+pub fn canonicalize_path_arg<P: AsRef<Path>>(path: P) -> CargoResult<PathBuf> {
+    Ok(path.as_ref().to_path_buf())
+}
+
+#[cfg(not(windows))]
+pub fn canonicalize_path_arg<P: AsRef<Path>>(path: P) -> CargoResult<PathBuf> {
+    Ok(fs::canonicalize(path)?)
+}
+
 fn add_path_args(bcx: &BuildContext<'_, '_>, unit: &Unit<'_>, cmd: &mut ProcessBuilder) {
     let (arg, cwd) = path_args(bcx, unit);
     cmd.arg(arg);

tests/testsuite/build.rs

@@ -4703,3 +4703,58 @@ d
         )
         .run();
 }
+
+#[cargo_test]
+#[cfg(not(target_os = "windows"))]
+fn symlink_rebuild() {
+    // Create a crate foo that depends on one crate: a.
+    // After the initial build we swap the 'a' directory for a symlink to 'b'.
+    // Since the underlying crate changed, cargo should perform a rebuild.
+    let project = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+                [dependencies]
+                a = { path = "a" }
+            "#,
+        )
+        .file("src/main.rs", "fn main(){}")
+        .file(
+            "a/Cargo.toml",
+            r#"
+                [package]
+                name = "a"
+                version = "0.1.0"
+            "#,
+        )
+        .file("a/src/lib.rs", "")
+        .file(
+            "b/Cargo.toml",
+            r#"
+                [package]
+                name = "a"
+                version = "0.1.0"
+            "#,
+        )
+        .file("b/src/lib.rs", "pub fn not_a(){}");
+
+    let foo = project.build();
+
+    foo.cargo("build -p foo")
+        .with_status(0)
+        .with_stderr_contains("[..] Compiling a v0.1.0 [..]")
+        .run();
+
+    let root = foo.root();
+
+    fs::remove_dir_all(root.join("a")).unwrap();
+    std::os::unix::fs::symlink(root.join("b"), root.join("a")).unwrap();
+
+    foo.cargo("build -p foo")
+        .with_status(0)
+        .with_stderr_contains("[..] Compiling a v0.1.0 [..]")
+        .run();
+}