2 files changed, 14 insertions, 1 deletions

diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index 81cb506b7..71976071f 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -19,6 +19,7 @@ use crate::Result;
 pub struct CargoWorkspace {
     packages: Arena<Package, PackageData>,
     targets: Arena<Target, TargetData>,
+    pub(crate) workspace_root: PathBuf,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
@@ -165,7 +166,7 @@ impl CargoWorkspace {
             }
         }
 
-        Ok(CargoWorkspace { packages, targets })
+        Ok(CargoWorkspace { packages, targets, workspace_root: meta.workspace_root })
     }
 
     pub fn packages<'a>(&'a self) -> impl Iterator<Item = Package> + 'a {
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index 3bad4f8d3..63eb7041e 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -255,6 +255,18 @@ impl ProjectWorkspace {
         }
         crate_graph
     }
+
+    pub fn workspace_root_for(&self, path: &Path) -> Option<&Path> {
+        match self {
+            ProjectWorkspace::Cargo { cargo, .. } => {
+                Some(cargo.workspace_root.as_ref()).filter(|root| path.starts_with(root))
+            }
+            ProjectWorkspace::Json { project: JsonProject { roots, .. } } => roots
+                .iter()
+                .find(|root| path.starts_with(&root.path))
+                .map(|root| root.path.as_ref()),
+        }
+    }
 }
 
 fn find_rust_project_json(path: &Path) -> Option<PathBuf> {