Throw when setting an invalid cursorStyle

Fixes #3477

demo/client.ts

@@ -173,6 +173,7 @@ function createTerminal(): void {
 
   const isWindows = ['Windows', 'Win16', 'Win32', 'WinCE'].indexOf(navigator.platform) >= 0;
   term = new Terminal({
+    allowTransparency: true,
     windowsMode: isWindows,
     fontFamily: 'Fira Code, courier-new, courier, monospace'
   } as ITerminalOptions);

src/common/Types.d.ts

@@ -35,6 +35,8 @@ export interface ITerminalOptions extends IPublicTerminalOptions {
   termName?: string;
 }
 
+export type CursorStyle = 'block' | 'underline' | 'bar';
+
 export type XtermListener = (...args: any[]) => void;
 
 /**

src/common/services/OptionsService.ts

@@ -6,6 +6,7 @@
 import { IOptionsService, ITerminalOptions, FontWeight } from 'common/services/Services';
 import { EventEmitter, IEvent } from 'common/EventEmitter';
 import { isMac } from 'common/Platform';
+import { CursorStyle } from 'common/Types';
 
 // Source: https://freesound.org/people/altemark/sounds/45759/
 // This sound is released under the Creative Commons Attribution 3.0 Unported
@@ -123,6 +124,14 @@ export class OptionsService implements IOptionsService {
 
   private _sanitizeAndValidateOption(key: string, value: any): any {
     switch (key) {
+      case 'cursorStyle':
+        if (!value) {
+          value = DEFAULT_OPTIONS[key];
+        }
+        if (!isCursorStyle(value)) {
+          throw new Error(`"${value}" is not a valid value for ${key}`);
+        }
+        break;
       case 'bellStyle':
       case 'cursorStyle':
       case 'rendererType':
@@ -176,3 +185,7 @@ export class OptionsService implements IOptionsService {
     return this.options[key];
   }
 }
+
+function isCursorStyle(value: unknown): value is CursorStyle {
+  return value === 'block' || value === 'underline' || value === 'bar';
+}

src/common/services/Services.ts

@@ -5,7 +5,7 @@
 
 import { IEvent, IEventEmitter } from 'common/EventEmitter';
 import { IBuffer, IBufferSet } from 'common/buffer/Types';
-import { IDecPrivateModes, ICoreMouseEvent, CoreMouseEncoding, ICoreMouseProtocol, CoreMouseEventType, ICharset, IWindowOptions, IModes, IAttributeData, ScrollSource, IDisposable, IColorRGB, IColor } from 'common/Types';
+import { IDecPrivateModes, ICoreMouseEvent, CoreMouseEncoding, ICoreMouseProtocol, CoreMouseEventType, ICharset, IWindowOptions, IModes, IAttributeData, ScrollSource, IDisposable, IColorRGB, IColor, CursorStyle } from 'common/Types';
 import { createDecorator } from 'common/services/ServiceRegistry';
 import { IDecorationOptions, IDecoration } from 'xterm';
 
@@ -217,7 +217,7 @@ export interface ITerminalOptions {
   cols: number;
   convertEol: boolean;
   cursorBlink: boolean;
-  cursorStyle: 'block' | 'underline' | 'bar';
+  cursorStyle: CursorStyle,
   cursorWidth: number;
   customGlyphs: boolean;
   disableStdin: boolean;