Merge #8955

8955: feature: Support standalone Rust files r=matklad a=SomeoneToIgnore

![standalone](https://user-images.githubusercontent.com/2690773/119277037-0b579380-bc26-11eb-8d77-20d46ab4916a.gif)

Closes https://github.com/rust-analyzer/rust-analyzer/issues/6388

Caveats: 

* I've decided to support multiple detached files in the code (anticipating the scratch files), but I found no way to open multiple files in VSCode at once: running `code *.rs` makes the plugin to register in the `vscode.workspace.textDocuments` only the first file, while code actually displays all files later.
Apparently what happens is the same as when you have VSCode open at some workplace already and then run `code some_other_file.rs`: it gets opened in the same workspace of the same VSCode with no server to support it.
If there's a way to override it, I'd appreciate the pointer.

* No way to toggle inlay hints, since the setting is updated for the workspace (which does not exist for a single file opened)
> [2021-05-24 00:22:49.100] [exthost] [error] Error: Unable to write to Workspace Settings because no workspace is opened. Please open a workspace first and try again.

* No runners/lens to run or check the code are implemented for this mode. 
In theory, we can detect `rustc`, run it on a file and run the resulting binary, but not sure if worth doing it at this stage.

Otherwise imports, hints, completion and other features work.

Co-authored-by: Kirill Bulatov <[email protected]>

1 files changed, 12 insertions, 2 deletions

diff --git a/editors/code/src/ctx.ts b/editors/code/src/ctx.ts
index bd023f803..22c5f62a1 100644
--- a/editors/code/src/ctx.ts
+++ b/editors/code/src/ctx.ts
@@ -7,6 +7,16 @@ import { createClient } from './client';
 import { isRustEditor, RustEditor } from './util';
 import { ServerStatusParams } from './lsp_ext';
 
+export type Workspace =
+    {
+        kind: 'Workspace Folder';
+        folder: vscode.Uri;
+    }
+    | {
+        kind: 'Detached Files';
+        files: vscode.TextDocument[];
+    };
+
 export class Ctx {
     private constructor(
         readonly config: Config,
@@ -22,9 +32,9 @@ export class Ctx {
         config: Config,
         extCtx: vscode.ExtensionContext,
         serverPath: string,
-        cwd: string,
+        workspace: Workspace,
     ): Promise<Ctx> {
-        const client = createClient(serverPath, cwd, config.serverExtraEnv);
+        const client = createClient(serverPath, workspace, config.serverExtraEnv);
 
         const statusBar = vscode.window.createStatusBarItem(vscode.StatusBarAlignment.Left);
         extCtx.subscriptions.push(statusBar);