Add ability to collect traces and log errors to log file

README.md

@@ -86,6 +86,8 @@ Set `go.useLanguageServer` to `true` to use the Go language server from [Sourceg
 * This is an experimental feature and is not available in Windows yet.
 * If set to true, you will be prompted to install the Go language server. Once installed, you will have to reload VS Code window. The language server will then be run by the Go extension in the background to provide services needed for the above mentioned features.
 * Everytime you change the value of the setting `go.useLanguageServer`, you need to reload the VS Code window for it to take effect.
+* To collect traces, set `"go.languageServerFlags": ["-trace"]`
+* To collect errors from language server in a logfile, set `"go.languageServerFlags": ["-trace", "-logfile", "path to a text file that exists" ]`
 
 
 ### Linter

package.json

@@ -485,6 +485,11 @@
           "default": false,
           "description": "Experimental: Not available in Windows. Use Go language server from Sourcegraph for Hover, Definition, Find All References, Signature Help, File Outline and Workspace Symbol features"
         },
+        "go.languageServerFlags": {
+          "type": "array",
+          "default": [],
+          "description": "Flags like -trace and -logfile to be used while running the language server."
+        },
         "go.gotoSymbol.includeImports": {
           "type": "boolean",
           "default": false,

src/goMain.ts

@@ -36,19 +36,19 @@ let diagnosticCollection: vscode.DiagnosticCollection;
 
 export function activate(ctx: vscode.ExtensionContext): void {
 	let useLangServer = vscode.workspace.getConfiguration('go')['useLanguageServer'];
+	let langServerFlags: string[] = vscode.workspace.getConfiguration('go')['languageServerFlags'] || [];
 	let toolsGopath = vscode.workspace.getConfiguration('go')['toolsGopath'];
 
 	updateGoPathGoRootFromConfig().then(() => {
 		offerToInstallTools();
 		let langServerAvailable = checkLanguageServer();
 		if (langServerAvailable) {
+			let langServerFlags: string[] = vscode.workspace.getConfiguration('go')['languageServerFlags'] || [];
 			const c = new LanguageClient(
 				'go-langserver',
 				{
 					command: getBinPath('go-langserver'),
-					args: [
-						'-mode=stdio'
-					],
+					args: ['-mode=stdio', ...langServerFlags],
 				},
 				{
 					documentSelector: ['go'],
@@ -143,7 +143,7 @@ export function activate(ctx: vscode.ExtensionContext): void {
 
 		// If there was a change in "useLanguageServer" setting, then ask the user to reload VS Code.
 		if (process.platform !== 'win32'
-			&& useLangServer !== updatedGoConfig['useLanguageServer']
+			&& didLangServerConfigChange(useLangServer, langServerFlags, updatedGoConfig)
 			&& (!updatedGoConfig['useLanguageServer'] || checkLanguageServer())) {
 			vscode.window.showInformationMessage('Reload VS Code window for the change in usage of language server to take effect', 'Reload').then(selected => {
 				if (selected === 'Reload') {
@@ -319,4 +319,18 @@ function sendTelemetryEventForConfig(goConfig: vscode.WorkspaceConfiguration) {
 		useLanguageServer: goConfig['useLanguageServer'] + '',
 		includeImports: goConfig['gotoSymbol'] && goConfig['gotoSymbol']['includeImports'] + ''
 	});
+}
+
+function didLangServerConfigChange(useLangServer: boolean, langServerFlags: string[], newconfig: vscode.WorkspaceConfiguration) {
+	let newLangServerFlags = newconfig['languageServerFlags'] || [];
+	if (useLangServer !== newconfig['useLanguageServer'] || langServerFlags.length !== newLangServerFlags.length) {
+		return true;
+	}
+
+	for (let i = 0; i < langServerFlags.length; i++) {
+		if (newLangServerFlags[i] !== langServerFlags[i]) {
+			return true;
+		}
+	}
+	return false;
 }