Auto merge of #17110 - Veykril:cargo-script-mvp, r=Veykril

Cargo script mvp

Based on #15456,

As the original PR stated, detached files are still horrendous to work with.

crates/load-cargo/src/lib.rs

@@ -335,7 +335,7 @@ fn load_crate_graph(
 ) -> RootDatabase {
     let (ProjectWorkspace::Cargo { toolchain, target_layout, .. }
     | ProjectWorkspace::Json { toolchain, target_layout, .. }
-    | ProjectWorkspace::DetachedFiles { toolchain, target_layout, .. }) = ws;
+    | ProjectWorkspace::DetachedFile { toolchain, target_layout, .. }) = ws;
 
     let lru_cap = std::env::var("RA_LRU_CAP").ok().and_then(|it| it.parse::<usize>().ok());
     let mut db = RootDatabase::new(lru_cap);

crates/project-model/src/cargo_workspace.rs

@@ -305,6 +305,12 @@ impl CargoWorkspace {
                     .collect(),
             );
         }
+        // The manifest is a rust file, so this means its a script manifest
+        if cargo_toml.extension().is_some_and(|ext| ext == "rs") {
+            // Deliberately don't set up RUSTC_BOOTSTRAP or a nightly override here, the user should
+            // opt into it themselves.
+            other_options.push("-Zscript".to_owned());
+        }
         meta.other_options(other_options);
 
         // FIXME: Fetching metadata is a slow process, as it might require
@@ -373,11 +379,12 @@ impl CargoWorkspace {
             let is_local = source.is_none();
             let is_member = ws_members.contains(&id);
 
+            let manifest = AbsPathBuf::assert(manifest_path);
             let pkg = packages.alloc(PackageData {
                 id: id.repr.clone(),
                 name,
                 version,
-                manifest: AbsPathBuf::assert(manifest_path).try_into().unwrap(),
+                manifest: manifest.clone().try_into().unwrap(),
                 targets: Vec::new(),
                 is_local,
                 is_member,
@@ -400,11 +407,22 @@ impl CargoWorkspace {
             for meta_tgt in meta_targets {
                 let cargo_metadata::Target { name, kind, required_features, src_path, .. } =
                     meta_tgt;
+                let kind = TargetKind::new(&kind);
                 let tgt = targets.alloc(TargetData {
                     package: pkg,
                     name,
-                    root: AbsPathBuf::assert(src_path),
-                    kind: TargetKind::new(&kind),
+                    root: if kind == TargetKind::Bin
+                        && manifest.extension().is_some_and(|ext| ext == "rs")
+                    {
+                        // cargo strips the script part of a cargo script away and places the
+                        // modified manifest file into a special target dir which is then used as
+                        // the source path. We don't want that, we want the original here so map it
+                        // back
+                        manifest.clone()
+                    } else {
+                        AbsPathBuf::assert(src_path)
+                    },
+                    kind,
                     required_features,
                 });
                 pkg_data.targets.push(tgt);