Flag errors in TSconfig.json (#19656)

Fixes #3783

From https://github.com/Microsoft/TypeScript/issues/10473

extensions/typescript/src/typescriptMain.ts

@@ -9,7 +9,7 @@
  * ------------------------------------------------------------------------------------------ */
 'use strict';
 
-import { env, languages, commands, workspace, window, ExtensionContext, Memento, IndentAction, Diagnostic, DiagnosticCollection, Range, DocumentFilter, Disposable } from 'vscode';
+import { env, languages, commands, workspace, window, ExtensionContext, Memento, IndentAction, Diagnostic, DiagnosticCollection, Range, DocumentFilter, Disposable, Uri } from 'vscode';
 
 // This must be the first statement otherwise modules might got loaded with
 // the wrong locale.
@@ -420,51 +420,52 @@ class TypeScriptServiceClientHost implements ITypescriptServiceClientHost {
 
 	/* internal */ configFileDiagnosticsReceived(event: Proto.ConfigFileDiagnosticEvent): void {
 		// See https://github.com/Microsoft/TypeScript/issues/10384
-		/* https://github.com/Microsoft/TypeScript/issues/10473
 		const body = event.body;
-		if (body.diagnostics) {
-			const language = body.triggerFile ? this.findLanguage(body.triggerFile) : this.findLanguage(body.configFile);
-			if (language) {
-				if (body.diagnostics.length === 0) {
-					language.configFileDiagnosticsReceived(body.configFile, []);
-				} else if (body.diagnostics.length >= 1) {
-					workspace.openTextDocument(Uri.file(body.configFile)).then((document) => {
-						let curly: [number, number, number] = undefined;
-						let nonCurly: [number, number, number] = undefined;
-						let diagnostic: Diagnostic;
-						for (let index = 0; index < document.lineCount; index++) {
-							let line = document.lineAt(index);
-							let text = line.text;
-							let firstNonWhitespaceCharacterIndex = line.firstNonWhitespaceCharacterIndex;
-							if (firstNonWhitespaceCharacterIndex < text.length) {
-								if (text.charAt(firstNonWhitespaceCharacterIndex) === '{') {
-									curly = [index, firstNonWhitespaceCharacterIndex, firstNonWhitespaceCharacterIndex + 1];
-									break;
-								} else {
-									let matches = /\s*([^\s]*)(?:\s*|$)/.exec(text.substr(firstNonWhitespaceCharacterIndex));
-									if (matches.length >= 1) {
-										nonCurly = [index, firstNonWhitespaceCharacterIndex, firstNonWhitespaceCharacterIndex + matches[1].length];
-									}
-								}
-							}
-						}
-						let match = curly || nonCurly;
-						if (match) {
-							diagnostic = new Diagnostic(new Range(match[0], match[1], match[0], match[2]), body.diagnostics[0].text);
+		if (!body || !body.diagnostics) {
+			return;
+		}
+
+		const language = body.triggerFile ? this.findLanguage(body.triggerFile) : this.findLanguage(body.configFile);
+		if (!language) {
+			return;
+		}
+		if (body.diagnostics.length === 0) {
+			language.configFileDiagnosticsReceived(body.configFile, []);
+		} else if (body.diagnostics.length >= 1) {
+			workspace.openTextDocument(Uri.file(body.configFile)).then((document) => {
+				let curly: [number, number, number] | undefined = undefined;
+				let nonCurly: [number, number, number] | undefined = undefined;
+				let diagnostic: Diagnostic;
+				for (let index = 0; index < document.lineCount; index++) {
+					const line = document.lineAt(index);
+					const text = line.text;
+					const firstNonWhitespaceCharacterIndex = line.firstNonWhitespaceCharacterIndex;
+					if (firstNonWhitespaceCharacterIndex < text.length) {
+						if (text.charAt(firstNonWhitespaceCharacterIndex) === '{') {
+							curly = [index, firstNonWhitespaceCharacterIndex, firstNonWhitespaceCharacterIndex + 1];
+							break;
 						} else {
-							diagnostic = new Diagnostic(new Range(0,0,0,0), body.diagnostics[0].text);
-						}
-						if (diagnostic) {
-							diagnostic.source = language.diagnosticSource;
-							language.configFileDiagnosticsReceived(body.configFile, [diagnostic]);
+							const matches = /\s*([^\s]*)(?:\s*|$)/.exec(text.substr(firstNonWhitespaceCharacterIndex));
+							if (matches && matches.length >= 1) {
+								nonCurly = [index, firstNonWhitespaceCharacterIndex, firstNonWhitespaceCharacterIndex + matches[1].length];
+							}
 						}
-					}, (error) => {
-						language.configFileDiagnosticsReceived(body.configFile, [new Diagnostic(new Range(0,0,0,0), body.diagnostics[0].text)]);
-					});
+					}
 				}
-			}
+				const match = curly || nonCurly;
+				if (match) {
+					diagnostic = new Diagnostic(new Range(match[0], match[1], match[0], match[2]), body.diagnostics[0].text);
+				} else {
+					diagnostic = new Diagnostic(new Range(0, 0, 0, 0), body.diagnostics[0].text);
+				}
+				if (diagnostic) {
+					diagnostic.source = language.diagnosticSource;
+					language.configFileDiagnosticsReceived(body.configFile, [diagnostic]);
+				}
+			}, (error) => {
+				language.configFileDiagnosticsReceived(body.configFile, [new Diagnostic(new Range(0, 0, 0, 0), body.diagnostics[0].text)]);
+			});
 		}
-		*/
 	}
 
 	private createMarkerDatas(diagnostics: Proto.Diagnostic[], source: string): Diagnostic[] {