src/extensionAPI: expose isPreview

Expose isPreview - whether the extension is running in preview mode
(e.g. a prerelease version) - in the extension API.

Also, fix a typo.

Updates #3651.

Change-Id: I991d3118d2f7786facb43d8252bf3e4fb294118d
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/653115
Reviewed-by: Hongxiang Jiang <hxjiang@golang.org>
kokoro-CI: kokoro <noreply+kokoro@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Madeline Kalil <mkalil@google.com>

Author: firelizzard18

extension/src/config.ts

@@ -37,7 +37,7 @@ export class ExtensionInfo {
 	readonly appName: string;
 	/** True if the extension runs in preview mode (e.g. Nightly, prerelease) */
 	readonly isPreview: boolean;
-	/** True if the extension runs in well-kwnon cloud IDEs */
+	/** True if the extension runs in well-known cloud IDEs */
 	readonly isInCloudIDE: boolean;
 
 	constructor() {

extension/src/export.d.ts

@@ -10,7 +10,20 @@ export interface CommandInvocation {
 	binPath: string;
 }
 
+/**
+ * The API we expose to other extensions.
+ *
+ * @example
+ * const Go = await vscode.extensions
+ *     .getExtension<ExtensionAPI>('golang.go')
+ *     .then(x => x.activate());
+ *
+ * console.log(`Go extension is a ${Go.isPreview ? 'preview' : 'release'} version`);
+ */
 export interface ExtensionAPI {
+	/** True if the extension is running in preview mode (e.g. prerelease) */
+	isPreview: boolean;
+
 	settings: {
 		/**
 		 * Returns the execution command corresponding to the specified resource, taking into account

extension/src/extensionAPI.ts

@@ -6,8 +6,11 @@
 import { Uri } from 'vscode';
 import { CommandInvocation, ExtensionAPI } from './export';
 import { getBinPathWithExplanation } from './util';
+import { extensionInfo } from './config';
 
 const api: ExtensionAPI = {
+	isPreview: extensionInfo.isPreview,
+
 	settings: {
 		getExecutionCommand(toolName: string, resource?: Uri): CommandInvocation | undefined {
 			const { binPath } = getBinPathWithExplanation(toolName, true, resource);