Allow having Cargo.toml in a subdirectory with rust-client.cargoSubdir

Fixes rust-lang#222.

This patch is quite hacky and may reveal my lack of knowledge on the RLS or
LSP architectures. My idea was to give the user the opportunity using the
variable `rust-client.cargoSubdir` to select a subdirectory as the root for
the Cargo.toml file.

To do that, I hacked the vscode's workspaceFoldervariable; my hack won't
work with multi-workspaces.

Alternate solutions:
- (not so good idea) add a new setting to the initialize JSON-RPC (similar
  to the existing `omitInitBuild` in the rls server) that would set a
  different path that the one given by vscode's workspaceFolder.
- (better) we add support for multi-root workspaces in the RLS server;
  (mentionned in  <rust-lang/rls#608>)
  but this does not really help when we want to open a general project
  where one of the subfolders is a rust project.
- we tell people that in order to get RLS working in a subdirectory, they
  must use the 'Multi-crate projects' feature or the 'rlsCommandOverride'
  feature (see README at <https://github.com/mehcode/atom-ide-rust>).

Author: maelvls

package.json

@@ -47,7 +47,8 @@
         "postinstall": "node ./node_modules/vscode/bin/install"
     },
     "dependencies": {
-        "vscode-languageclient": "^4.1.4"
+        "vscode-languageclient": "^4.1.4",
+        "path": "^0.12.0"
     },
     "devDependencies": {
         "@types/mocha": "^2.2.43",
@@ -191,6 +192,11 @@
                     "default": "rls-preview",
                     "description": "Name of the RLS rustup component."
                 },
+                "rust-client.cargoSubdir": {
+                    "type": "string",
+                    "default": "",
+                    "description": "Relative path to Cargo.toml. By default, it is workspace root."
+                },
                 "rust.sysroot": {
                     "type": [
                         "string",

src/configuration.ts

@@ -40,6 +40,7 @@ export class RLSConfiguration {
      * If specified, RLS will be spawned by executing a file at the given path.
      */
     public readonly rlsPath: string | null;
+    public readonly cargoSubdir: string | null;
 
     public static loadFromWorkspace(): RLSConfiguration {
         const configuration = workspace.getConfiguration();
@@ -66,6 +67,7 @@ export class RLSConfiguration {
         if (!this.rlsPath) {
             this.rlsPath = rlsPath;
         }
+        this.cargoSubdir = configuration.get('rust-client.cargoSubdir', null);
     }
 
     private static readRevealOutputChannelOn(configuration: WorkspaceConfiguration) {

src/extension.ts

@@ -17,9 +17,10 @@ import { activateTaskProvider, deactivateTaskProvider } from './tasks';
 
 import * as child_process from 'child_process';
 import * as fs from 'fs';
+import * as path from 'path';
 
 import { commands, ExtensionContext, IndentAction, languages, TextEditor,
-    TextEditorEdit, window, workspace } from 'vscode';
+    TextEditorEdit, window, workspace, Uri } from 'vscode';
 import { LanguageClient, LanguageClientOptions, Location, NotificationType,
     ServerOptions } from 'vscode-languageclient';
 import { execFile, ExecChildProcessResult } from './utils/child_process';
@@ -82,14 +83,19 @@ async function makeRlsProcess(): Promise<child_process.ChildProcess> {
     const rls_path = CONFIGURATION.rlsPath;
 
     let childProcessPromise: Promise<child_process.ChildProcess>;
+    const cargoSubdir = workspace.getConfiguration().get('rust-client.cargoSubdir');
+    const cargo_toml_path = workspace.rootPath + ( cargoSubdir ? '/'+cargoSubdir : '');
     if (rls_path) {
         const env = await makeRlsEnv(true);
-        console.info('running ' + rls_path);
-        childProcessPromise = Promise.resolve(child_process.spawn(rls_path, [], { env }));
+        console.info('running ' + rls_path + ' using CWD "'+cargo_toml_path+'"');
+        childProcessPromise = Promise.resolve(child_process.spawn(rls_path, [], { cwd: cargo_toml_path, env }));
     } else {
         const env = await makeRlsEnv();
-        console.info('running with rustup');
-        childProcessPromise = runRlsViaRustup(env);
+        console.info('running with rustup using CWD "'+cargo_toml_path+'"');
+        const env_2 = {...env, cwd: cargo_toml_path};
+        console.info(env_2);
+        console.info(cargo_toml_path);
+        childProcessPromise = runRlsViaRustup(env_2);
     }
     try {
         const childProcess = await childProcessPromise;
@@ -134,7 +140,7 @@ export async function activate(context: ExtensionContext) {
 }
 
 async function startLanguageClient(context: ExtensionContext) {
-    if (workspace.rootPath === undefined) {
+    if (workspace.rootPath === undefined || !workspace.workspaceFolders) {
         window.showWarningMessage('Startup error: the RLS can only operate on a folder, not a single file');
         return;
     }
@@ -154,6 +160,8 @@ async function startLanguageClient(context: ExtensionContext) {
         await autoUpdate();
         return makeRlsProcess();
     };
+    const cargoSubdir = workspace.getConfiguration().get('rust-client.cargoSubdir');
+    const workspaceFolder = workspace.workspaceFolders[0];
     const clientOptions: LanguageClientOptions = {
         // Register the server for Rust files
         documentSelector: [
@@ -164,6 +172,8 @@ async function startLanguageClient(context: ExtensionContext) {
         // Controls when to focus the channel rather than when to reveal it in the drop-down list
         revealOutputChannelOn: CONFIGURATION.revealOutputChannelOn,
         initializationOptions: { omitInitBuild: true },
+        workspaceFolder: {...workspaceFolder,
+            uri: Uri.parse('file://' + workspace.rootPath + (cargoSubdir ? '/'+cargoSubdir : ''))}
     };
 
     // Create the language client and start the client.
@@ -186,10 +196,34 @@ export function deactivate(): Promise<void> {
 }
 
 async function warnOnMissingCargoToml() {
-    const files = await workspace.findFiles('Cargo.toml');
-
-    if (files.length < 1) {
-        window.showWarningMessage('A Cargo.toml file must be at the root of the workspace in order to support all features');
+    const setting_section = 'rust-client.cargoSubdir';
+    const root_toml_files = await workspace.findFiles('Cargo.toml');
+
+    if (root_toml_files.length < 1) {
+        const subdir_toml_files = await workspace.findFiles('**/Cargo.toml');
+        const setting_value = workspace.getConfiguration().get(setting_section);
+        if (subdir_toml_files.length < 1) {
+            window.showWarningMessage(`The Cargo.toml file has not been found at
+            the root of the workspace or anywhere else. In order to support all
+            RLS features, some Cargo.toml must be present.`);
+
+        } else if (! setting_value) {
+            const subdir = path.dirname(workspace.asRelativePath(subdir_toml_files[0]));
+            const item_save_to_settings = `Save to '.vscode/settings.json'`;
+            window.showWarningMessage(`A Cargo.toml has been found in the sudirectory '${subdir}/'.
+            Although RLS expects Cargo.toml to be at the root of the workspace,
+            we can set this path using the '${setting_section}' setting in your
+            '.vscode/settings.json'`, ...[item_save_to_settings])
+                .then(v => {
+                    switch (v) {
+                        case item_save_to_settings:
+                            workspace.getConfiguration().update(setting_section, subdir);
+                            break;
+                        default:
+                            break;
+                    }
+                });
+        }
     }
 }