Contextual Logger - Initial Implementation

logger.js

const pino = require('pino');

function createLogger(opts, destination) {
  return pino(opts, destination);
}

module.exports = createLogger;

logger.test.js

const test = require('ava');
const parseJSONStream = require('./utils/parse-json-stream');
const streamToGenerator = require('./utils/stream-to-generator');
const createLogger = require('./logger');

async function testMethod(t, input = {}, expected = {}) {
  const { method } = input;
  const { level } = expected;

  const stream = parseJSONStream();
  const logger = createLogger({ level: 'trace' }, stream);

  const gen = streamToGenerator(stream);

  logger[method]('foo');

  const data = await gen.next().value;

  t.is(data.level, level);
}

const loggerMethodUseCases = [
  { input: { method: 'trace' }, expected: { level: 10 } },
  { input: { method: 'debug' }, expected: { level: 20 } },
  { input: { method: 'info' }, expected: { level: 30 } },
  { input: { method: 'warn' }, expected: { level: 40 } },
  { input: { method: 'error' }, expected: { level: 50 } },
  { input: { method: 'fatal' }, expected: { level: 60 } },
];

loggerMethodUseCases.forEach(({ input, expected }) => {
  test(
    `Logger methods: ${JSON.stringify(input)} - ${JSON.stringify(expected)}`,
    testMethod,
    input,
    expected
  );
});

parse-json-stream.js

const { Transform } = require('stream');

const parseJSONStream = () =>
  new Transform({
    objectMode: true,
    transform(chunk, encoding, cb) {
      try {
        const data = JSON.parse(chunk.toString('utf8'));
        return cb(null, data);
      } catch (err) {
        return cb(err);
      }
    },
  });

module.exports = parseJSONStream;

stream-to-generator.js

function* streamToGenerator(stream) {
  while (true) {
    const res = yield Promise.race([
      new Promise(resolve => stream.once('data', resolve)),
      new Promise(resolve => stream.once('end', resolve)),
      new Promise((resolve, reject) => stream.once('end', reject)),
    ]);

    if (!res) {
      break;
    }
  }
}

module.exports = streamToGenerator;