Slightly more robust cargo watcher root search

crates/ra_lsp_server/src/world.rs

@@ -74,7 +74,7 @@ impl WorldState {
         lru_capacity: Option<usize>,
         exclude_globs: &[Glob],
         watch: Watch,
-        options: Options,
+        mut options: Options,
         feature_flags: FeatureFlags,
     ) -> WorldState {
         let mut change = AnalysisChange::new();
@@ -132,8 +132,20 @@ impl WorldState {
         change.set_crate_graph(crate_graph);
 
         // FIXME: Figure out the multi-workspace situation
-        let check_watcher =
-            CheckWatcher::new(&options.cargo_watch, folder_roots.first().cloned().unwrap());
+        let check_watcher = {
+            let first_workspace = workspaces.first().unwrap();
+            let cargo_project_root = match first_workspace {
+                ProjectWorkspace::Cargo { cargo, .. } => cargo.workspace_root.clone(),
+                ProjectWorkspace::Json { .. } => {
+                    log::warn!(
+                        "Cargo check watching only supported for cargo workspaces, disabling"
+                    );
+                    options.cargo_watch.enable = false;
+                    PathBuf::new()
+                }
+            };
+            CheckWatcher::new(&options.cargo_watch, cargo_project_root)
+        };
 
         let mut analysis_host = AnalysisHost::new(lru_capacity, feature_flags);
         analysis_host.apply_change(change);

crates/ra_project_model/src/cargo_workspace.rs

@@ -21,7 +21,7 @@ use crate::Result;
 pub struct CargoWorkspace {
     packages: Arena<Package, PackageData>,
     targets: Arena<Target, TargetData>,
-    pub(crate) workspace_root: PathBuf,
+    pub workspace_root: PathBuf,
 }
 
 #[derive(Deserialize, Clone, Debug, PartialEq, Eq)]