Summary

Adds a WebWritableStream class that wraps the Parser using the Web Streams API's WritableStream, enabling direct piping from fetch() response bodies into the parser.

Closes #1862

Motivation

The existing WritableStream wraps Node.js stream.Writable, which is incompatible with the Web Streams API. Users in browsers, Deno, Bun, or modern Node.js cannot pipe a fetch() response body into the parser without manual glue code.

Design

• New file: src/WritableStreamWeb.ts — a WebWritableStream class extending globalThis.WritableStream<string | Uint8Array>
• Subpath export: htmlparser2/WebWritableStream (mirrors the existing htmlparser2/WritableStream pattern)
• Constructor: (cbs: Partial<Handler>, options?: ParserOptions) — same signature as the Node.js WritableStream
• Chunk handling: accepts string (passed directly) and Uint8Array (decoded via TextDecoder in streaming mode for correct multi-byte UTF-8 handling)
• Lifecycle: write() sink calls parser.write(), close() sink flushes the decoder then calls parser.end()

Usage

import { WebWritableStream } from "htmlparser2/WebWritableStream";

const stream = new WebWritableStream({
    onopentag(name, attribs) {
        console.log("Opened:", name);
    },
    ontext(text) {
        console.log("Text:", text);
    },
});

const response = await fetch("https://example.com");
await response.body.pipeTo(stream);

Test plan

• Fragmented UTF-8 decoding via split Uint8Array chunks
• String chunk handling
• Empty stream (verifies onend fires)
• Abort signal (verifies neither ontext nor onend fires)
• ReadableStream.pipeTo() integration with HTML parsing assertions
• Snapshot tests for all 6 fixture documents (Basic.html, Attributes.html, Svg.html, RSS, Atom, RDF)
• Single-pass vs streamed consistency verification for each fixture
• All existing 103 tests continue to pass (114 total with the 11 new tests)
• ESLint, TypeScript (tsc --noEmit), and Biome all clean