eventsource-parser 3.1.0: EventSourceParserStream

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify eventsource-parser.EventSourceParserStream in pkg:npm/eventsource-parser@3.1.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/eventsource-parser@3.1.0
Demonstrate these symbols/APIs:
  - eventsource-parser.EventSourceParserStream

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:9956da406ed8e903f481f472534f0a2142c292931ee43e33333a395aa677995a","contract":["assert EventSourceParserStream transforms chunked string streams into EventSourceMessage objects","assert EventSourceParserStream extracts event types and message ids from streamed events","assert EventSourceParserStream triggers onRetry and onComment callbacks during streaming","assert EventSourceParserStream emits ParseError to onError callback or terminates when configured","assert EventSourceParserStream errors the stream when maxBufferSize is exceeded"],"goal":"verify eventsource-parser.EventSourceParserStream in pkg:npm/eventsource-parser@3.1.0","kind":"HOW","packages":["pkg:npm/eventsource-parser@3.1.0"],"schemaVersion":1,"symbols":["eventsource-parser.EventSourceParserStream"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/eventsource-parser@3.1.0"],"schemaVersion":1,"subject":"pkg:npm/eventsource-parser@3.1.0","symbols":["eventsource-parser.EventSourceParserStream"],"verifierAdapter":"node-typescript@1"}

import { EventSourceParserStream, ParseError } from 'eventsource-parser/stream';

/**
 * Creates an EventSourceParserStream transform stream.
 * @param {import('eventsource-parser/stream').StreamOptions} [options]
 * @returns {EventSourceParserStream}
 */
export function createEventSourceStream(options) {
  return new EventSourceParserStream(options);
}

export { EventSourceParserStream, ParseError };
export default EventSourceParserStream;

{
  "name": "sample-eventsource-parser-stream-verify",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-eventsource-parser-stream-verify",
      "version": "1.0.0",
      "dependencies": {
        "eventsource-parser": "3.1.0"
      }
    },
    "node_modules/eventsource-parser": {
      "version": "3.1.0",
      "resolved": "https://registry.npmjs.org/eventsource-parser/-/eventsource-parser-3.1.0.tgz",
      "integrity": "sha512-kJezFj9YFAMLeORyi7aCLxLbD5/qWMQnoMVlVPyHIll7lgRJCc3JVln9Vgl9nwQi0YkMnhdGTMNn7CkRRAptMg==",
      "license": "MIT",
      "engines": {
        "node": ">=18.0.0"
      }
    }
  }
}

{
  "name": "sample-eventsource-parser-stream-verify",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "dependencies": {
    "eventsource-parser": "3.1.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify eventsource-parser.EventSourceParserStream in pkg:npm/eventsource-parser@3.1.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/eventsource-parser@3.1.0"
  ],
  "symbols": [
    "eventsource-parser.EventSourceParserStream"
  ]
}

import assert from 'node:assert/strict';
import { EventSourceParserStream, ParseError, createEventSourceStream } from '../index.mjs';

async function collectStreamEvents(readable) {
  const reader = readable.getReader();
  const events = [];
  while (true) {
    const { done, value } = await reader.read();
    if (done) break;
    events.push(value);
  }
  return events;
}

// 1. assert EventSourceParserStream transforms chunked string streams into EventSourceMessage objects
{
  const stream = new ReadableStream({
    start(controller) {
      controller.enqueue('data: chunk');
      controller.enqueue('ed message\n\n');
      controller.close();
    },
  });

  const parsedEvents = await collectStreamEvents(stream.pipeThrough(new EventSourceParserStream()));
  assert.strictEqual(parsedEvents.length, 1);
  assert.deepStrictEqual(parsedEvents[0], {
    id: undefined,
    event: undefined,
    data: 'chunked message',
  });
}

// 2. assert EventSourceParserStream extracts event types and message ids from streamed events
{
  const stream = new ReadableStream({
    start(controller) {
      controller.enqueue('id: 101\nevent: update\ndata: first event\n\n');
      controller.enqueue('id: 102\nevent: completion\ndata: second event\n\n');
      controller.close();
    },
  });

  const parsedEvents = await collectStreamEvents(stream.pipeThrough(createEventSourceStream()));
  assert.strictEqual(parsedEvents.length, 2);
  assert.strictEqual(parsedEvents[0].id, '101');
  assert.strictEqual(parsedEvents[0].event, 'update');
  assert.strictEqual(parsedEvents[0].data, 'first event');

  assert.strictEqual(parsedEvents[1].id, '102');
  assert.strictEqual(parsedEvents[1].event, 'completion');
  assert.strictEqual(parsedEvents[1].data, 'second event');
}

// 3. assert EventSourceParserStream triggers onRetry and onComment callbacks during streaming
{
  const retries = [];
  const comments = [];
  const stream = new ReadableStream({
    start(controller) {
      controller.enqueue(': connection keep-alive\nretry: 2500\ndata: payload\n\n');
      controller.close();
    },
  });

  const parsedEvents = await collectStreamEvents(
    stream.pipeThrough(
      new EventSourceParserStream({
        onRetry: (interval) => retries.push(interval),
        onComment: (comment) => comments.push(comment),
      })
    )
  );

  assert.strictEqual(parsedEvents.length, 1);
  assert.strictEqual(parsedEvents[0].data, 'payload');
  assert.deepStrictEqual(retries, [2500]);
  assert.deepStrictEqual(comments, ['connection keep-alive']);
}

// 4. assert EventSourceParserStream emits ParseError to onError callback or terminates when configured
{
  const errors = [];
  const streamWithCallback = new ReadableStream({
    start(controller) {
      controller.enqueue('bad_field: test\ndata: still parsed\n\n');
      controller.close();
    },
  });

  const parsedEvents = await collectStreamEvents(
    streamWithCallback.pipeThrough(
      new EventSourceParserStream({
        onError: (err) => errors.push(err),
      })
    )
  );

  assert.strictEqual(parsedEvents.length, 1);
  assert.strictEqual(errors.length, 1);
  assert.ok(errors[0] instanceof ParseError);
  assert.strictEqual(errors[0].type, 'unknown-field');

  const streamWithTerminate = new ReadableStream({
    start(controller) {
      controller.enqueue('bad_field: test\n\n');
      controller.close();
    },
  });

  let terminated = false;
  try {
    await collectStreamEvents(
      streamWithTerminate.pipeThrough(new EventSourceParserStream({ onError: 'terminate' }))
    );
  } catch (err) {
    terminated = true;
    assert.ok(err instanceof ParseError);
    assert.strictEqual(err.type, 'unknown-field');
  }
  assert.strictEqual(terminated, true);
}

// 5. assert EventSourceParserStream errors the stream when maxBufferSize is exceeded
{
  const stream = new ReadableStream({
    start(controller) {
      controller.enqueue('data: ' + 'x'.repeat(100));
      controller.close();
    },
  });

  let bufferErrorThrown = false;
  try {
    await collectStreamEvents(
      stream.pipeThrough(new EventSourceParserStream({ maxBufferSize: 20 }))
    );
  } catch (err) {
    bufferErrorThrown = true;
    assert.ok(err instanceof ParseError);
    assert.strictEqual(err.type, 'max-buffer-size-exceeded');
  }
  assert.strictEqual(bufferErrorThrown, true);
}

console.log('All EventSourceParserStream contract assertions passed.');