Adding Workspace DIR functionality

src/cargo/core/workspace.rs

@@ -201,6 +201,17 @@ impl<'cfg> Workspace<'cfg> {
         }.parent().unwrap()
     }
 
+    /// Returns the root path of this workspace.
+    ///
+    /// That is, this returns the path of the directory containing the
+    /// `Cargo.toml` which is the root of this workspace.
+    pub fn workspace_dir(&self) -> Option<&Path> {
+        match self.root_manifest {
+            Some(ref p) => p.parent(),
+            None => None
+        }
+    }
+
     pub fn target_dir(&self) -> Filesystem {
         self.target_dir.clone().unwrap_or_else(|| {
             Filesystem::new(self.root().join("target"))

src/cargo/ops/cargo_rustc/custom_build.rs

@@ -120,6 +120,10 @@ fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
         cmd.env("CARGO_MANIFEST_LINKS", links);
     }
 
+    if let Some(ws_dir) = cx.ws.workspace_dir() {
+        cmd.env("CARGO_WORKSPACE_DIR", ws_dir);
+    }
+
     // Be sure to pass along all enabled features for this package, this is the
     // last piece of statically known information that we have.
     for feat in cx.resolve.features(unit.pkg.package_id()).iter() {

src/doc/environment-variables.md

@@ -75,6 +75,8 @@ let out_dir = env::var("OUT_DIR").unwrap();
                          script). Also note that this is the value of the
                          current working directory of the build script when it
                          starts.
+* `CARGO_WORKSPACE_DIR` - The directory containing the manifest of the workspace,
+                          for the package being built.
 * `CARGO_MANIFEST_LINKS` - the manifest `links` value.
 * `CARGO_FEATURE_<name>` - For each activated feature of the package being
                            built, this environment variable will be present

tests/workspaces.rs

@@ -1469,3 +1469,72 @@ Caused by:
 "));
 }
 
+fn missing_workspace_build_dir(){
+    let p = project("foo")
+    .file("Cargo.toml", r#"
+        [project]
+        name = "foo"
+        version = "0.5.0"
+        authors = []
+    "#)
+    .file("src/lib.rs", "")
+    .file("build.rs", r#"
+        fn main() {
+            use std::env;
+            use std::env::VarError::NotPresent;
+
+            assert_eq!(env::var("CARGO_WORSPACE_DIR"), Err(NotPresent));
+        }
+    "#);
+    p.build();
+
+    assert_that(p.cargo("build"),
+                execs().with_status(0));
+}
+
+#[test]
+fn workspace_build_dir(){
+    let p = project("foo")
+    .file("Cargo.toml", r#"
+        [project]
+        name = "foo"
+        version = "0.5.0"
+        authors = []
+
+
+        [workspace]
+        members = ["bar"]
+    "#)
+    .file("src/lib.rs", "")
+    .file("build.rs", r#"
+        use std::env;
+
+        fn main() {
+            assert!(env::var("CARGO_WORKSPACE_DIR").unwrap().ends_with("foo"));
+        }
+    "#)
+    .file("bar/Cargo.toml", r#"
+        [project]
+        name = "bar"
+        version = "0.5.0"
+        authors = []
+        links = "bar"
+        build = "build.rs"
+    "#)
+    .file("bar/src/lib.rs", "")
+    .file("bar/build.rs", r#"
+        use std::env;
+
+        fn main() {
+            assert!(env::var("CARGO_WORKSPACE_DIR").unwrap().ends_with("foo"));
+        }
+    "#);
+    p.build();
+
+    assert_that(p.cargo("build"),
+                execs().with_status(0));
+    assert_that(&p.root().join("target"), existing_dir());
+    assert_that(p.cargo("build").cwd(p.root().join("bar")),
+                execs().with_status(0));
+}
+