eventsource-parser 3.1.1: EventSourceParser

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 EventSourceParser in pkg:npm/eventsource-parser@3.1.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/eventsource-parser@3.1.1
Demonstrate these symbols/APIs:
  - EventSourceParser
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:b987c91379c625a6c3d201d51faccb6bc1b6a1c8e4408b074ea64dd72fd4bc8e","constraints":{"executionContext":"node"},"contract":["createParser returns an EventSourceParser instance with feed and reset methods","EventSourceParser parses basic messages, multiline data, event types, and message IDs","EventSourceParser streams partial chunks across line and message boundaries","EventSourceParser emits comment and retry events to their respective callbacks","EventSourceParser handles reset and reports invalid retry or unknown fields","EventSourceParser enforces maxBufferSize and throws on subsequent feed until reset"],"goal":"verify EventSourceParser in pkg:npm/eventsource-parser@3.1.1","kind":"HOW","packages":["pkg:npm/eventsource-parser@3.1.1"],"schemaVersion":1,"symbols":["EventSourceParser"]},"contractCommand":["node","test/contract.js"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/eventsource-parser@3.1.1"],"schemaVersion":1,"subject":"pkg:npm/eventsource-parser@3.1.1","symbols":["EventSourceParser"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-eventsource-parser",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-eventsource-parser",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "eventsource-parser": "3.1.1"
      }
    },
    "node_modules/eventsource-parser": {
      "version": "3.1.1",
      "resolved": "https://registry.npmjs.org/eventsource-parser/-/eventsource-parser-3.1.1.tgz",
      "integrity": "sha512-EKN1vKAMcZ8MlYMpaNuxN6R9yakzH6uajHcHVTqWJzvu5pWw9DyhbP35HH8MVBQ+dZjAfDxk+A8NiR9KWaXiyQ==",
      "license": "MIT",
      "engines": {
        "node": ">=18.0.0"
      }
    }
  }
}

{
  "name": "sample-eventsource-parser",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification sample for EventSourceParser in eventsource-parser",
  "main": "src/index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "eventsource-parser": "3.1.1"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify EventSourceParser in pkg:npm/eventsource-parser@3.1.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/eventsource-parser@3.1.1"
  ],
  "symbols": [
    "EventSourceParser"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

const { createParser, ParseError } = require('eventsource-parser');

/**
 * Creates an EventSource parser instance with given callbacks and options.
 * @param {import('eventsource-parser').ParserConfig} config
 * @returns {import('eventsource-parser').EventSourceParser}
 */
function createEventParser(config) {
  return createParser(config);
}

/**
 * Feeds SSE chunked stream into a new parser and collects parsed events.
 * @param {string[]} chunks
 * @param {import('eventsource-parser').ParserConfig} [config]
 * @returns {Array<import('eventsource-parser').EventSourceMessage>}
 */
function parseChunks(chunks, config = {}) {
  const events = [];
  const parser = createParser({
    ...config,
    onEvent: (event) => {
      events.push(event);
      if (config.onEvent) config.onEvent(event);
    }
  });

  for (const chunk of chunks) {
    parser.feed(chunk);
  }

  return events;
}

module.exports = {
  createParser,
  createEventParser,
  parseChunks,
  ParseError
};

const assert = require('node:assert/strict');
const { createParser, ParseError } = require('eventsource-parser');
const { createEventParser, parseChunks } = require('../src/index.js');

// 1. createParser returns an EventSourceParser instance with feed and reset methods
{
  const parser = createParser({ onEvent: () => {} });
  assert.equal(typeof parser.feed, 'function', 'parser.feed should be a function');
  assert.equal(typeof parser.reset, 'function', 'parser.reset should be a function');
  assert.throws(() => createParser(() => {}), TypeError);

  const wrappedParser = createEventParser({ onEvent: () => {} });
  assert.equal(typeof wrappedParser.feed, 'function');
  assert.equal(typeof wrappedParser.reset, 'function');
}

// 2. EventSourceParser parses basic messages, multiline data, event types, and message IDs
{
  const events = [];
  const parser = createParser({
    onEvent: (event) => events.push(event)
  });

  parser.feed('data: hello world\n\n');
  assert.deepEqual(events[0], {
    id: undefined,
    event: undefined,
    data: 'hello world'
  });

  parser.feed('id: 42\nevent: custom-event\ndata: line 1\ndata: line 2\n\n');
  assert.deepEqual(events[1], {
    id: '42',
    event: 'custom-event',
    data: 'line 1\nline 2'
  });

  assert.equal(events.length, 2);
}

// 3. EventSourceParser streams partial chunks across line and message boundaries
{
  const events = [];
  const parser = createParser({
    onEvent: (event) => events.push(event)
  });

  parser.feed('\xEF\xBB\xBFdata: hel');
  assert.equal(events.length, 0);

  parser.feed('lo\n');
  assert.equal(events.length, 0);

  parser.feed('\n');
  assert.equal(events.length, 1);
  assert.deepEqual(events[0], {
    id: undefined,
    event: undefined,
    data: 'hello'
  });

  const parsedFromHelper = parseChunks(['data: ch', 'unk1\n\n', 'data: chunk2\n\n']);
  assert.equal(parsedFromHelper.length, 2);
  assert.equal(parsedFromHelper[0].data, 'chunk1');
  assert.equal(parsedFromHelper[1].data, 'chunk2');
}

// 4. EventSourceParser emits comment and retry events to their respective callbacks
{
  const comments = [];
  const retries = [];
  const parser = createParser({
    onComment: (comment) => comments.push(comment),
    onRetry: (retry) => retries.push(retry)
  });

  parser.feed(': this is a comment\n\n');
  assert.deepEqual(comments, ['this is a comment']);

  parser.feed('retry: 5000\n\n');
  assert.deepEqual(retries, [5000]);
}

// 5. EventSourceParser handles reset and reports invalid retry or unknown fields
{
  const errors = [];
  const parser = createParser({
    onError: (err) => errors.push(err)
  });

  parser.feed('retry: not-a-number\n\n');
  assert.equal(errors.length, 1);
  assert.equal(errors[0].type, 'invalid-retry');
  assert(errors[0] instanceof ParseError);

  parser.feed('unknown-field: some-value\n\n');
  assert.equal(errors.length, 2);
  assert.equal(errors[1].type, 'unknown-field');

  // reset with consume parses trailing incomplete line
  parser.feed('trailing-invalid: foo');
  parser.reset({ consume: true });
  assert.equal(errors.length, 3);
  assert.equal(errors[2].type, 'unknown-field');
}

// 6. EventSourceParser enforces maxBufferSize and throws on subsequent feed until reset
{
  const errors = [];
  const parser = createParser({
    maxBufferSize: 10,
    onError: (err) => errors.push(err)
  });

  parser.feed('data: unclosed line exceeding buffer size');
  assert.equal(errors.length, 1);
  assert.equal(errors[0].type, 'max-buffer-size-exceeded');
  assert(errors[0] instanceof ParseError);

  // Feeding terminated parser throws
  assert.throws(() => parser.feed('data: test\n\n'), /Cannot feed parser/);

  // Calling reset allows feeding again
  parser.reset();
  parser.feed('data: ok\n\n');
}

console.log('Contract tests passed successfully.');