From 6cce6f606aae1d1cbd46fa0ddc7cfa2edfc39746 Mon Sep 17 00:00:00 2001
From: Nicolas Mattia <nicolas@nmattia.com>
Date: Wed, 3 Jul 2019 17:38:26 +0200
Subject: [PATCH 1/3] Test that cargo rebuilds if symlink changed target

---
 tests/testsuite/build.rs | 55 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/tests/testsuite/build.rs b/tests/testsuite/build.rs
index e1fae224237..2bd36af1c9e 100644
--- a/tests/testsuite/build.rs
+++ b/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();
+}

From 854f8757a4094fd77f9ad3a94cb0840e36f6fb6c Mon Sep 17 00:00:00 2001
From: Nicolas Mattia <nicolas@nmattia.com>
Date: Fri, 28 Jun 2019 15:34:08 +0200
Subject: [PATCH 2/3] Canonicalize path_args src

---
 src/cargo/core/compiler/mod.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/cargo/core/compiler/mod.rs b/src/cargo/core/compiler/mod.rs
index 628ac8bbff8..5c8728d683b 100644
--- a/src/cargo/core/compiler/mod.rs
+++ b/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);

From 979904e092b39bb6aafe62a3ff3d994d3d8b6247 Mon Sep 17 00:00:00 2001
From: Nicolas Mattia <nicolas@nmattia.com>
Date: Thu, 4 Jul 2019 12:50:40 +0200
Subject: [PATCH 3/3] Fix formatting

---
 tests/testsuite/build.rs | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/tests/testsuite/build.rs b/tests/testsuite/build.rs
index 2bd36af1c9e..8f1c6891111 100644
--- a/tests/testsuite/build.rs
+++ b/tests/testsuite/build.rs
@@ -4707,7 +4707,6 @@ d
 #[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.
@@ -4723,25 +4722,26 @@ fn symlink_rebuild() {
             "#,
         )
         .file("src/main.rs", "fn main(){}")
-        .file("a/Cargo.toml",
-              r#"
-                  [package]
-                  name = "a"
-                  version = "0.1.0"
-              "#,
-            )
+        .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/Cargo.toml",
+            r#"
+                [package]
+                name = "a"
+                version = "0.1.0"
+            "#,
+        )
         .file("b/src/lib.rs", "pub fn not_a(){}");
 
-    let foo = project
-        .build();
+    let foo = project.build();
 
     foo.cargo("build -p foo")
         .with_status(0)