Better encapsulate reverse-mapping of files to cargo targets

We need to find a better way to do it...

CrateGraph by itself is fine, CargoWorkspace as well, but the mapping
between the two seems arbitrary...

crates/rust-analyzer/src/cargo_target_spec.rs

@@ -2,7 +2,7 @@
 
 use ra_cfg::CfgExpr;
 use ra_ide::{FileId, RunnableKind, TestId};
-use ra_project_model::{self, ProjectWorkspace, TargetKind};
+use ra_project_model::{self, TargetKind};
 
 use crate::{global_state::GlobalStateSnapshot, Result};
 
@@ -89,27 +89,23 @@ pub(crate) fn runnable_args(
     }
 
     pub(crate) fn for_file(
-        world: &GlobalStateSnapshot,
+        global_state_snapshot: &GlobalStateSnapshot,
         file_id: FileId,
     ) -> Result<Option<CargoTargetSpec>> {
-        let &crate_id = match world.analysis().crate_for(file_id)?.first() {
-            Some(crate_id) => crate_id,
+        let crate_id = match global_state_snapshot.analysis().crate_for(file_id)?.first() {
+            Some(crate_id) => *crate_id,
             None => return Ok(None),
         };
-        let file_id = world.analysis().crate_root(crate_id)?;
-        let path = world.file_id_to_path(file_id);
-        let res = world.workspaces.iter().find_map(|ws| match ws {
-            ProjectWorkspace::Cargo { cargo, .. } => {
-                let tgt = cargo.target_by_root(&path)?;
-                Some(CargoTargetSpec {
-                    package: cargo.package_flag(&cargo[cargo[tgt].package]),
-                    target: cargo[tgt].name.clone(),
-                    target_kind: cargo[tgt].kind,
-                })
-            }
-            ProjectWorkspace::Json { .. } => None,
-        });
-        Ok(res)
+        let (cargo_ws, target) = match global_state_snapshot.cargo_target_for_crate_root(crate_id) {
+            Some(it) => it,
+            None => return Ok(None),
+        };
+        let res = CargoTargetSpec {
+            package: cargo_ws.package_flag(&cargo_ws[cargo_ws[target].package]),
+            target: cargo_ws[target].name.clone(),
+            target_kind: cargo_ws[target].kind,
+        };
+        Ok(Some(res))
     }
 
     pub(crate) fn push_to(self, buf: &mut Vec<String>, kind: &RunnableKind) {

crates/rust-analyzer/src/global_state.rs

@@ -15,7 +15,7 @@
 use ra_ide::{
     Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, LibraryData, SourceRootId,
 };
-use ra_project_model::{ProcMacroClient, ProjectWorkspace};
+use ra_project_model::{CargoWorkspace, ProcMacroClient, ProjectWorkspace, Target};
 use ra_vfs::{LineEndings, RootEntry, Vfs, VfsChange, VfsFile, VfsTask, Watch};
 use relative_path::RelativePathBuf;
 use stdx::format_to;
@@ -28,7 +28,7 @@
     vfs_glob::{Glob, RustPackageFilterBuilder},
     LspError, Result,
 };
-use ra_db::ExternSourceId;
+use ra_db::{CrateId, ExternSourceId};
 use rustc_hash::{FxHashMap, FxHashSet};
 
 fn create_flycheck(workspaces: &[ProjectWorkspace], config: &FlycheckConfig) -> Option<Flycheck> {
@@ -290,10 +290,6 @@ pub fn file_id_to_url(&self, id: FileId) -> Url {
         file_id_to_url(&self.vfs.read(), id)
     }
 
-    pub fn file_id_to_path(&self, id: FileId) -> PathBuf {
-        self.vfs.read().file2path(VfsFile(id.0))
-    }
-
     pub fn file_line_endings(&self, id: FileId) -> LineEndings {
         self.vfs.read().file_line_endings(VfsFile(id.0))
     }
@@ -305,6 +301,20 @@ pub fn anchored_path(&self, file_id: FileId, path: &str) -> Url {
         url_from_abs_path(&path)
     }
 
+    pub(crate) fn cargo_target_for_crate_root(
+        &self,
+        crate_id: CrateId,
+    ) -> Option<(&CargoWorkspace, Target)> {
+        let file_id = self.analysis().crate_root(crate_id).ok()?;
+        let path = self.vfs.read().file2path(VfsFile(file_id.0));
+        self.workspaces.iter().find_map(|ws| match ws {
+            ProjectWorkspace::Cargo { cargo, .. } => {
+                cargo.target_by_root(&path).map(|it| (cargo, it))
+            }
+            ProjectWorkspace::Json { .. } => None,
+        })
+    }
+
     pub fn status(&self) -> String {
         let mut buf = String::new();
         if self.workspaces.is_empty() {