Validate target in the options

package.json

@@ -1,6 +1,6 @@
 {
   "name": "webm-muxer",
-  "version": "5.0.1",
+  "version": "5.0.2",
   "description": "WebM multiplexer in pure TypeScript with support for WebCodecs API, video & audio.",
   "main": "./build/webm-muxer.js",
   "module": "./build/webm-muxer.mjs",

src/index.ts

@@ -1,3 +1,3 @@
 export { Muxer } from './muxer';
 export { SubtitleEncoder } from './subtitles';
-export * from './target';
+export { ArrayBufferTarget, StreamTarget, FileSystemWritableFileStreamTarget } from './target';

src/muxer.ts

@@ -22,7 +22,7 @@ const CODEC_PRIVATE_MAX_SIZE = 2**12;
 const APP_NAME = 'https://github.com/Vanilagy/webm-muxer';
 const SEGMENT_SIZE_BYTES = 6;
 const CLUSTER_SIZE_BYTES = 5;
-const FIRST_TIMESTAMP_BEHAVIORS = ['strict',  'offset', 'permissive'] as const;
+const FIRST_TIMESTAMP_BEHAVIORS = ['strict', 'offset', 'permissive'] as const;
 
 interface MuxerOptions<T extends Target> {
 	target: T,
@@ -136,6 +136,10 @@ export class Muxer<T extends Target> {
 			throw new TypeError('The muxer requires an options object to be passed to its constructor.');
 		}
 
+		if (!(options.target instanceof Target)) {
+			throw new TypeError('The target must be provided and an instance of Target.');
+		}
+
 		if (options.video) {
 			if (typeof options.video.codec !== 'string') {
 				throw new TypeError(`Invalid video codec: ${options.video.codec}. Must be a string.`);

src/target.ts

@@ -1,17 +1,23 @@
-export type Target = ArrayBufferTarget | StreamTarget | FileSystemWritableFileStreamTarget;
+const isTarget = Symbol('isTarget');
+export abstract class Target {
+	// If we didn't add this symbol, then {} would be assignable to Target
+	[isTarget]: true;
+}
 
-export class ArrayBufferTarget {
+export class ArrayBufferTarget extends Target {
 	buffer: ArrayBuffer = null;
 }
 
-export class StreamTarget {
+export class StreamTarget extends Target {
 	constructor(public options: {
 		onData?: (data: Uint8Array, position: number) => void,
 		onHeader?: (data: Uint8Array, position: number) => void,
 		onCluster?: (data: Uint8Array, position: number, timestamp: number) => void,
 		chunked?: boolean,
 		chunkSize?: number
 	}) {
+		super();
+
 		if (typeof options !== 'object') {
 			throw new TypeError('StreamTarget requires an options object to be passed to its constructor.');
 		}
@@ -44,11 +50,13 @@ export class StreamTarget {
 	}
 }
 
-export class FileSystemWritableFileStreamTarget {
+export class FileSystemWritableFileStreamTarget extends Target {
 	constructor(
 		public stream: FileSystemWritableFileStream,
 		public options?: { chunkSize?: number }
 	) {
+		super();
+
 		if (!(stream instanceof FileSystemWritableFileStream)) {
 			throw new TypeError('FileSystemWritableFileStreamTarget requires a FileSystemWritableFileStream instance.');
 		}

tsconfig.json

@@ -1,11 +1,10 @@
 {
 	"compilerOptions": {
-		"target": "ES2015",
+		"target": "ES2021",
 		"strict": true,
 		"strictNullChecks": false,
 		"noImplicitAny": true,
-		"noImplicitOverride": true,
-		"types": ["Node", "@types/wicg-file-system-access", "@types/dom-webcodecs"]
+		"noImplicitOverride": true
 	},
 	"include": [
 		"src/**/*",