Ensure that we throw and capture error output if the process fails to start

Author: dibarbet

package.json

@@ -1130,6 +1130,12 @@
             "scope": "machine-overridable",
             "description": "%configuration.dotnet.server.path%"
           },
+          "dotnet.server.startTimeout": {
+            "type": "number",
+            "scope": "machine-overridable",
+            "default": 30000,
+            "description": "%configuration.dotnet.server.startTimeout%"
+          },
           "dotnet.server.waitForDebugger": {
             "type": "boolean",
             "scope": "machine-overridable",

package.nls.json

@@ -2,6 +2,7 @@
   "configuration.dotnet.defaultSolution.description": "The path of the default solution to be opened in the workspace, or set to 'disable' to skip it. (Previously `omnisharp.defaultLaunchSolution`)",
   "configuration.dotnet.dotnetPath": "Specifies the path to a dotnet installation directory to use instead of the default system one. This only influences the dotnet installation to use for hosting the language server itself. Example: \"/home/username/mycustomdotnetdirectory\".",
   "configuration.dotnet.server.path": "Specifies the absolute path to the server (LSP or O#) executable. When left empty the version pinned to the C# Extension is used. (Previously `omnisharp.path`)",
+  "configuration.dotnet.server.startTimeout": "Specifies a timeout (in ms) for the client to successfully start and connect to the language server.",
   "configuration.dotnet.server.waitForDebugger": "Passes the --debug flag when launching the server to allow a debugger to be attached. (Previously `omnisharp.waitForDebugger`)",
   "configuration.dotnet.server.trace": "Sets the logging level for the language server",
   "configuration.dotnet.server.extensionPaths": "Override for path to language server --extension arguments",

src/lsptoolshost/roslynLanguageServer.ts

@@ -532,9 +532,28 @@ export class RoslynLanguageServer {
             childProcess = cp.spawn(serverPath, args, cpOptions);
         }
 
+        // Record the stdout and stderr streams from the server process.
+        childProcess.stdout.on('data', (data: { toString: (arg0: any) => any }) => {
+            const result: string = isString(data) ? data : data.toString(RoslynLanguageServer.encoding);
+            _channel.append('[stdout] ' + result);
+        });
+        childProcess.stderr.on('data', (data: { toString: (arg0: any) => any }) => {
+            const result: string = isString(data) ? data : data.toString(RoslynLanguageServer.encoding);
+            _channel.append('[stderr] ' + result);
+        });
+
         // Timeout promise used to time out the connection process if it takes too long.
-        const timeout = new Promise<undefined>((resolve) => {
-            RAL().timer.setTimeout(resolve, 30000);
+        const timeout = new Promise<undefined>((resolve, reject) => {
+            RAL().timer.setTimeout(resolve, languageServerOptions.startTimeout);
+
+            // If the child process exited unexpectedly, reject the promise early.
+            // Error information will be captured from the stdout/stderr streams above.
+            childProcess.on('exit', (code) => {
+                if (code && code !== 0) {
+                    _channel.appendLine(`Language server process exited with ${code}`);
+                    reject();
+                }
+            });
         });
 
         // The server process will create the named pipe used for communcation. Wait for it to be created,
@@ -543,8 +562,6 @@ export class RoslynLanguageServer {
             _channel.appendLine('waiting for named pipe information from server...');
             childProcess.stdout.on('data', (data: { toString: (arg0: any) => any }) => {
                 const result: string = isString(data) ? data : data.toString(RoslynLanguageServer.encoding);
-                _channel.append('[stdout] ' + result);
-
                 // Use the regular expression to find all JSON lines
                 const jsonLines = result.match(RoslynLanguageServer.namedPipeKeyRegex);
                 if (jsonLines) {

src/shared/options.ts

@@ -72,6 +72,7 @@ export interface LanguageServerOptions {
     readonly logLevel: string;
     readonly documentSelector: DocumentSelector;
     readonly extensionsPaths: string[] | null;
+    readonly startTimeout: number;
 }
 
 export interface RazorOptions {
@@ -377,6 +378,9 @@ class LanguageServerOptionsImpl implements LanguageServerOptions {
     public get extensionsPaths() {
         return readOption<string[] | null>('dotnet.server.extensionPaths', null);
     }
+    public get startTimeout() {
+        return readOption<number>('dotnet.server.startTimeout', 30000);
+    }
 }
 
 class RazorOptionsImpl implements RazorOptions {