Should explicitly report the fatal settings error

package.json

@@ -543,7 +543,7 @@
         },
         "java.format.settings.url": {
           "type": "string",
-          "markdownDescription": "Specifies the url or file path to the [Eclipse formatter xml settings](https://github.com/redhat-developer/vscode-java/wiki/Formatter-settings).",
+          "markdownDescription": "Specifies the url or file path to the Eclipse formatter xml. \n\nFor example: \n\n`\"java.format.settings.url\":\"file://home/myuser/format.xml\"`\n\n `\"java.format.settings.url\": \"https://raw.githubusercontent.com/google/styleguide/gh-pages/eclipse-java-google-style.xml\"`\n\n`\"java.format.settings.url\":\".vscode/format.xml\"`\n\n `\"java.format.settings.url\":\".vscode\\\\format.xml\" (Windows)` \n\n`\"java.format.settings.url\":\"file:///C:/Users/MyUser/format.xml\" (Windows)` \n\n`\"java.format.settings.url\":\"C:\\\\Users\\\\MyUser\\\\format.xml\" (Windows)` \n\nSee [Eclipse formatter xml settings](https://github.com/redhat-developer/vscode-java/wiki/Formatter-settings).",
           "default": null,
           "scope": "window"
         },
@@ -839,7 +839,7 @@
         },
         "java.settings.url": {
           "type": "string",
-          "markdownDescription": "Specifies the url or file path to the workspace Java settings. See [Setting Global Preferences](https://github.com/redhat-developer/vscode-java/wiki/Settings-Global-Preferences)",
+          "markdownDescription": "Specifies the url or file path to the workspace Java settings. \n\nFor example: \n\n`\"java.settings.url\":\"file://home/myuser/settings.prefs\"`\n\n`\"java.settings.url\":\".vscode/settings.prefs\"`\n\n `\"java.settings.url\":\".vscode\\\\settings.prefs\" (Windows)` \n\n`\"java.settings.url\":\"file:///C:/Users/MyUser/settings.prefs\" (Windows)` \n\n`\"java.settings.url\":\"C:\\\\Users\\\\MyUser\\\\settings.prefs\" (Windows)` \n\nSee [Setting Global Preferences](https://github.com/redhat-developer/vscode-java/wiki/Settings-Global-Preferences)",
           "default": null,
           "scope": "window"
         },

src/extension.ts

@@ -14,7 +14,7 @@ import { initialize as initializeRecommendation } from './recommendation';
 import { Commands } from './commands';
 import { ExtensionAPI, ClientStatus } from './extension.api';
 import { getJavaConfiguration, deleteDirectory, getBuildFilePatterns, getInclusionPatternsFromNegatedExclusion, convertToGlob, getExclusionBlob, ensureExists } from './utils';
-import { onConfigurationChange, getJavaServerMode, ServerMode, ACTIVE_BUILD_TOOL_STATE, handleTextBlockClosing } from './settings';
+import { onConfigurationChange, getJavaServerMode, ServerMode, ACTIVE_BUILD_TOOL_STATE, handleTextBlockClosing, checkJavaPreferences, checkSettings, isRemote } from './settings';
 import { logger, initializeLogFile } from './log';
 import glob = require('glob');
 import { SyntaxLanguageClient } from './syntaxLanguageClient';
@@ -185,6 +185,10 @@ export function activate(context: ExtensionContext): Promise<ExtensionAPI> {
 
 	cleanJavaWorkspaceStorage();
 
+	checkSettings('format.settings.url');
+
+	checkSettings('settings.url');
+
 	serverStatusBarProvider.initialize();
 
 	return requirements.resolveRequirements(context).catch(error => {
@@ -856,10 +860,6 @@ function openDocument(extensionPath, formatterUrl, defaultFormatter, relativePat
 		});
 }
 
-function isRemote(f) {
-	return f !== null && f.startsWith('http:/') || f.startsWith('https:/') || f.startsWith('file:/');
-}
-
 async function addFormatter(extensionPath, formatterUrl, defaultFormatter, relativePath) {
 	const options: InputBoxOptions = {
 		value: (relativePath ? relativePath : formatterUrl),

src/settings.ts

@@ -2,6 +2,7 @@
 
 import * as fs from 'fs';
 import * as path from 'path';
+import * as url from 'url';
 import { window, Uri, workspace, WorkspaceConfiguration, commands, ConfigurationTarget, env, ExtensionContext, TextEditor, Range, Disposable, WorkspaceFolder, TextDocument, Position, SnippetString, TextLine } from 'vscode';
 import { Commands } from './commands';
 import { cleanWorkspaceFileName } from './extension';
@@ -55,6 +56,8 @@ export function onConfigurationChange(workspacePath: string) {
 		}
 		// update old config
 		oldConfig = newConfig;
+		checkSettings('format.settings.url');
+		checkSettings('settings.url');
 	});
 }
 
@@ -319,3 +322,42 @@ export function handleTextBlockClosing(document: TextDocument, changes: readonly
 		}
 	}
 }
+
+export function checkSettings(preferenceName) {
+	const preference: string = getJavaConfiguration().get(preferenceName);
+	let show = false;
+	if (isRemote(preference)) {
+		try {
+			const fileUrl = new url.URL(preference);
+			const protocol = fileUrl.protocol;
+			if (protocol === 'file:') {
+				show = !fs.existsSync(fileUrl);
+				if (!show) {
+					show = !preference.startsWith("file:///") && (preference.startsWith("file://") || !preference.startsWith("file:/"));
+				}
+			}
+		} catch (err) {
+			show = true;
+		}
+	} else if (preference !== null && !fs.existsSync(preference)) {
+		show = true;
+	}
+	if (show) {
+		const msg = `The 'java.${preferenceName}=${preference}' preference is not valid.`;
+		const action = 'Open settings';
+		const restartId = Commands.OPEN_JSON_SETTINGS;
+		window.showWarningMessage(msg, action).then((selection) => {
+			if (action === selection) {
+				commands.executeCommand(restartId, `java.${preferenceName}`);
+			}
+		});
+	}
+}
+
+export function isRemote(f) {
+	if (f !== null) {
+		const protocol = url.parse(f).protocol;
+		return protocol !== null && (protocol === 'file:' || protocol === 'http:' || protocol === 'https:');
+	}
+	return false;
+}