Use public extension API to fetch the current client workspace

It seems that we do not share that on Windows the same way we do on the
other platforms, so make sure to go through the 'blessed' way of
fetching the public API that's returned by extension's `activate`
function.

This should fix tests on all platforms.

Author: Xanewok

test/suite/extension.test.ts

@@ -5,17 +5,25 @@ import * as vscode from 'vscode';
 import { Disposable, Uri } from 'vscode';
 
 import * as extension from '../../src/extension';
+import { Observable } from '../../src/utils/observable';
 
 const fixtureDir = path.resolve(
   path.join(__dirname, '..', '..', '..', 'fixtures'),
 );
 
 suite('Extension Tests', () => {
   test('cargo tasks are auto-detected', async () => {
+    // Activate manually to ease the access to internal, exported APIs without
+    // having to open any file before
+    const ext = vscode.extensions.getExtension<extension.Api>(
+      'rust-lang.rust',
+    )!;
+    const { activeWorkspace } = await ext.activate();
+
     const projects = [
       path.join(fixtureDir, 'bare-lib-project'),
       path.join(fixtureDir, 'another-lib-project'),
-    ];
+    ].map(path => Uri.file(path).fsPath);
 
     const expected = [
       { subcommand: 'build', group: vscode.TaskGroup.Build, cwd: projects[0] },
@@ -26,10 +34,9 @@ suite('Extension Tests', () => {
       { subcommand: 'run', group: undefined },
     ];
 
-    const whenWorkspacesActive = projects.map(path => {
-      const fsPath = Uri.file(path).fsPath;
-      return whenWorkspaceActive(fsPath);
-    });
+    const whenWorkspacesActive = projects.map(path =>
+      whenWorkspaceActive(activeWorkspace, path),
+    );
 
     // This makes sure that we set the focus on the opened files (which is what
     // actually triggers the extension for the project)
@@ -89,11 +96,12 @@ async function currentTasksInclude(
  * @param fsPath normalized file system path of a URI
  */
 function whenWorkspaceActive(
+  observable: Observable<extension.ClientWorkspace | null>,
   fsPath: string,
 ): Promise<extension.ClientWorkspace> {
   return new Promise(resolve => {
     let disposable: Disposable | undefined;
-    disposable = extension.activeWorkspace.observe(value => {
+    disposable = observable.observe(value => {
       if (value && value.folder.uri.fsPath === fsPath) {
         if (disposable) {
           disposable.dispose();