4 files changed, 72 insertions, 6 deletions

diff --git a/editors/code/src/client.ts b/editors/code/src/client.ts
index d72ecc58f..f909f8db2 100644
--- a/editors/code/src/client.ts
+++ b/editors/code/src/client.ts
@@ -30,15 +30,14 @@ export function configToServerOptions(config: Config) {
     };
 }
 
-export async function createClient(config: Config, serverPath: string): Promise<lc.LanguageClient> {
+export async function createClient(config: Config, serverPath: string, cwd: string): Promise<lc.LanguageClient> {
     // '.' Is the fallback if no folder is open
     // TODO?: Workspace folders support Uri's (eg: file://test.txt).
     // It might be a good idea to test if the uri points to a file.
-    const workspaceFolderPath = vscode.workspace.workspaceFolders?.[0]?.uri.fsPath ?? '.';
 
     const run: lc.Executable = {
         command: serverPath,
-        options: { cwd: workspaceFolderPath },
+        options: { cwd },
     };
     const serverOptions: lc.ServerOptions = {
         run,
diff --git a/editors/code/src/ctx.ts b/editors/code/src/ctx.ts
index d2f49cd23..86b5f3629 100644
--- a/editors/code/src/ctx.ts
+++ b/editors/code/src/ctx.ts
@@ -15,8 +15,13 @@ export class Ctx {
 
     }
 
-    static async create(config: Config, extCtx: vscode.ExtensionContext, serverPath: string): Promise<Ctx> {
-        const client = await createClient(config, serverPath);
+    static async create(
+        config: Config,
+        extCtx: vscode.ExtensionContext,
+        serverPath: string,
+        cwd: string,
+    ): Promise<Ctx> {
+        const client = await createClient(config, serverPath, cwd);
         const res = new Ctx(config, extCtx, client, serverPath);
         res.pushCleanup(client.start());
         await client.onReady();
diff --git a/editors/code/src/main.ts b/editors/code/src/main.ts
index a46dbde33..7ba16120c 100644
--- a/editors/code/src/main.ts
+++ b/editors/code/src/main.ts
@@ -13,6 +13,7 @@ import { log, assert } from './util';
 import { PersistentState } from './persistent_state';
 import { fetchRelease, download } from './net';
 import { spawnSync } from 'child_process';
+import { activateTaskProvider } from './tasks';
 
 let ctx: Ctx | undefined;
 
@@ -41,11 +42,18 @@ export async function activate(context: vscode.ExtensionContext) {
     const state = new PersistentState(context.globalState);
     const serverPath = await bootstrap(config, state);
 
+    const workspaceFolder = vscode.workspace.workspaceFolders?.[0];
+    if (workspaceFolder === undefined) {
+        const err = "Cannot activate rust-analyzer when no folder is opened";
+        void vscode.window.showErrorMessage(err);
+        throw new Error(err);
+    }
+
     // Note: we try to start the server before we activate type hints so that it
     // registers its `onDidChangeDocument` handler before us.
     //
     // This a horribly, horribly wrong way to deal with this problem.
-    ctx = await Ctx.create(config, context, serverPath);
+    ctx = await Ctx.create(config, context, serverPath, workspaceFolder.uri.fsPath);
 
     // Commands which invokes manually via command palette, shortcut, etc.
 
@@ -85,6 +93,8 @@ export async function activate(context: vscode.ExtensionContext) {
     ctx.registerCommand('applySourceChange', commands.applySourceChange);
     ctx.registerCommand('selectAndApplySourceChange', commands.selectAndApplySourceChange);
 
+    ctx.pushCleanup(activateTaskProvider(workspaceFolder));
+
     activateStatusDisplay(ctx);
 
     if (!ctx.config.highlightingSemanticTokens) {
diff --git a/editors/code/src/tasks.ts b/editors/code/src/tasks.ts
new file mode 100644
index 000000000..fa1c4a951
--- /dev/null
+++ b/editors/code/src/tasks.ts
@@ -0,0 +1,52 @@
+import * as vscode from 'vscode';
+
+// This ends up as the `type` key in tasks.json. RLS also uses `cargo` and
+// our configuration should be compatible with it so use the same key.
+const TASK_TYPE = 'cargo';
+
+export function activateTaskProvider(target: vscode.WorkspaceFolder): vscode.Disposable {
+    const provider: vscode.TaskProvider = {
+        // Detect Rust tasks. Currently we do not do any actual detection
+        // of tasks (e.g. aliases in .cargo/config) and just return a fixed
+        // set of tasks that always exist. These tasks cannot be removed in
+        // tasks.json - only tweaked.
+        provideTasks: () => getStandardCargoTasks(target),
+
+        // We don't need to implement this.
+        resolveTask: () => undefined,
+    };
+
+    return vscode.tasks.registerTaskProvider(TASK_TYPE, provider);
+}
+
+function getStandardCargoTasks(target: vscode.WorkspaceFolder): vscode.Task[] {
+    return [
+        { command: 'build', group: vscode.TaskGroup.Build },
+        { command: 'check', group: vscode.TaskGroup.Build },
+        { command: 'test', group: vscode.TaskGroup.Test },
+        { command: 'clean', group: vscode.TaskGroup.Clean },
+        { command: 'run', group: undefined },
+    ]
+        .map(({ command, group }) => {
+            const vscodeTask = new vscode.Task(
+                // The contents of this object end up in the tasks.json entries.
+                {
+                    type: TASK_TYPE,
+                    command,
+                },
+                // The scope of the task - workspace or specific folder (global
+                // is not supported).
+                target,
+                // The task name, and task source. These are shown in the UI as
+                // `${source}: ${name}`, e.g. `rust: cargo build`.
+                `cargo ${command}`,
+                'rust',
+                // What to do when this command is executed.
+                new vscode.ShellExecution('cargo', [command]),
+                // Problem matchers.
+                ['$rustc'],
+            );
+            vscodeTask.group = group;
+            return vscodeTask;
+        });
+}