Provide actionable steps to the user when an OmniSharp server specifi…

…c to the current Linux distribution can't be found

src/omnisharpServer.ts

@@ -264,7 +264,7 @@ export abstract class OmnisharpServer {
 		this._fireEvent(Events.StdOut, `[INFO] Starting OmniSharp at '${solutionPath}'...\n`);
 		this._fireEvent(Events.BeforeServerStart, solutionPath);
 
-		return omnisharpLauncher(cwd, argv).then(value => {
+		return omnisharpLauncher(this._channel, cwd, argv).then(value => {
 			this._serverProcess = value.process;
             this._requestDelays = {};
             this._fireEvent(Events.StdOut, `[INFO] Started OmniSharp from '${value.command}' with process id ${value.process.pid}...\n`);

src/omnisharpServerLauncher.ts

@@ -7,11 +7,12 @@
 
 import {exists as fileExists} from 'fs';
 import {spawn, ChildProcess} from 'child_process';
-import {workspace} from 'vscode';
+import {workspace, OutputChannel} from 'vscode';
 import {satisfies} from 'semver';
 import {join} from 'path';
 import {getOmnisharpLaunchFilePath} from './omnisharpPath';
 import {downloadOmnisharp} from './omnisharpDownload';
+import {SupportedPlatform, getSupportedPlatform} from './utils';
 
 const isWindows = process.platform === 'win32';
 
@@ -20,20 +21,33 @@ export interface LaunchResult {
     command: string;
 }
 
-export function installOmnisharpIfNeeded(): Promise<string> {
+export function installOmnisharpIfNeeded(output: OutputChannel): Promise<string> {
     return getOmnisharpLaunchFilePath().catch(err => {
+        if (getSupportedPlatform() == SupportedPlatform.None && process.platform === 'linux') {
+            output.appendLine("[ERROR] Could not locate an OmniSharp server that supports your Linux distribution.");
+            output.appendLine("");
+            output.appendLine("OmniSharp provides a richer C# editing experience, with features like IntelliSense and Find All References.");
+            output.appendLine("It is recommend that you download the version of OmniSharp that runs on Mono using the following steps:");
+            output.appendLine("    1. If it's not already installed, download and install Mono (http://www.mono-project.com)");
+            output.appendLine("    2. Download and untar https://github.com/OmniSharp/omnisharp-roslyn/releases/download/v1.9-alpha13/omnisharp-linux-mono.tar.gz");
+            output.appendLine("    3. In Visual Studio Code, select Preferences->User Settings to open settings.json.");
+            output.appendLine("    4. In settings.json, add a new setting: \"csharp.omnisharp\": \"/path/to/omnisharp/OmniSharp.exe\"");
+            output.appendLine("    5. Restart Visual Studio Code.");
+            throw err;
+        }
+
         return downloadOmnisharp().then(_ => {
             return getOmnisharpLaunchFilePath();
         })
     });
 }
 
-export default function launch(cwd: string, args: string[]): Promise<LaunchResult> {
+export default function launch(output: OutputChannel, cwd: string, args: string[]): Promise<LaunchResult> {
 
 	return new Promise<LaunchResult>((resolve, reject) => {
 
 		try {
-			(isWindows ? launchWindows(cwd, args) : launchNix(cwd, args)).then(value => {
+			(isWindows ? launchWindows(output, cwd, args) : launchNix(output, cwd, args)).then(value => {
 
 				// async error - when target not not ENEOT
 				value.process.on('error', reject);
@@ -52,8 +66,8 @@ export default function launch(cwd: string, args: string[]): Promise<LaunchResul
 	});
 }
 
-function launchWindows(cwd: string, args: string[]): Promise<LaunchResult> {
-	return installOmnisharpIfNeeded().then(command => {
+function launchWindows(output: OutputChannel, cwd: string, args: string[]): Promise<LaunchResult> {
+	return installOmnisharpIfNeeded(output).then(command => {
 
 		args = args.slice(0);
 		args.unshift(command);
@@ -77,9 +91,9 @@ function launchWindows(cwd: string, args: string[]): Promise<LaunchResult> {
 	});
 }
 
-function launchNix(cwd: string, args: string[]): Promise<LaunchResult>{
+function launchNix(output: OutputChannel, cwd: string, args: string[]): Promise<LaunchResult>{
 
-    return installOmnisharpIfNeeded().then(command => {
+    return installOmnisharpIfNeeded(output).then(command => {
 		let process = spawn(command, args, {
 			detached: false,
 			// env: details.env,