Support offline usage

Only log a warning instead of throwing an exception if the user is
offline and a valid version of the language server/debug adapter is
installed.

Author: fwcd

src/debugSetup.ts

@@ -18,7 +18,7 @@ export async function registerDebugAdapter(context: vscode.ExtensionContext, sta
 			await debugAdapterDownloader.downloadServerIfNeeded(status);
 		} catch (error) {
 			console.error(error);
-			vscode.window.showErrorMessage(`Could not download debug adapter: ${error}`);
+			vscode.window.showWarningMessage(`Could not update/download Kotlin Debug Adapter: ${error}`);
 			return;
 		}
 	}

src/languageSetup.ts

@@ -23,8 +23,8 @@ export async function activateLanguageServer(context: vscode.ExtensionContext, s
         try {
             await langServerDownloader.downloadServerIfNeeded(status);
         } catch (error) {
-            console.error(error);
-            vscode.window.showErrorMessage(`Could not download language server: ${error}`);
+			console.error(error);
+            vscode.window.showWarningMessage(`Could not update/download Kotlin Language Server: ${error}`);
             return;
         }
     }

src/serverDownloader.ts

@@ -78,16 +78,33 @@ export class ServerDownloader {
 	}
 
 	async downloadServerIfNeeded(status: Status): Promise<void> {
-		const serverInfo = (await this.installedServerInfo()) || { version: "0.0.0", lastUpdate: Number.MIN_SAFE_INTEGER };
-		const secondsSinceLastUpdate = (Date.now() - serverInfo.lastUpdate) / 1000;
+		const serverInfo = await this.installedServerInfo();
+		const serverInfoOrDefault = serverInfo || { version: "0.0.0", lastUpdate: Number.MIN_SAFE_INTEGER };
+		const secondsSinceLastUpdate = (Date.now() - serverInfoOrDefault.lastUpdate) / 1000;
 
 		if (secondsSinceLastUpdate > 480) {
 			// Only query GitHub API for latest version if some time has passed
-			LOG.info("Querying GitHub API for new KLS version...");
+			LOG.info(`Querying GitHub API for new ${this.displayName} version...`);
+			
+			let releaseInfo: GitHubReleasesAPIResponse;
+			
+			try {
+				releaseInfo = await this.latestReleaseInfo();
+			} catch (error) {
+				const message = `Could not fetch from GitHub releases API: ${error}.`;
+				if (serverInfo == null) {
+					// No server is installed yet, so throw
+					throw new Error(message);
+				} else {
+					// Do not throw since user might just be offline
+					// and a version of the server is already installed
+					LOG.warn(message);
+					return;
+				}
+			}
 
-			const releaseInfo = await this.latestReleaseInfo();
 			const latestVersion = releaseInfo.tag_name;
-			const installedVersion = serverInfo.version;
+			const installedVersion = serverInfoOrDefault.version;
 			const serverNeedsUpdate = semver.gt(latestVersion, installedVersion);
 			let newVersion = installedVersion;