Add the ability to access logs in sendTransaction

[janhesters]

Issue To Be Solved

When you log inside a transaction there is no easy way to access those logs inside of your code / tests.

(Optional): Suggest A Solution

Solution 1: add logs to the return value of sendTransaction

Currently, sendTransaction returns an object with 4 keys.

type ReturnValue = {
  status: number;
  statusCode: number;
  errorMessage: string;
  events: Events[];
}

We could add a fifth value logs

type ReturnValue = {
  // ...
  logs: string[];
}

---

Solution 2: use spyOn on console.log

You can spy on console.log after activating emulator.start to read logs in tests:

it('given a transaction: logs out the signers', async () => {
  const message = 'Hello from Emulator';
  const Alice = await getAccountAddress('Alice');
  const Bob = await getAccountAddress('Bob');
  const signers = [Alice, Bob];

  const consoleSpy = jest
    .spyOn(console, 'log')
    // eslint-disable-next-line @typescript-eslint/no-empty-function
    .mockImplementation(() => {});
  emulator.setLogging(true);

  await sendTransaction({
    name: 'log-signers',
    args: [message],
    signers,
  });

  const transactionLogs = consoleSpy.mock.calls.toString();
  consoleSpy.mockRestore();

  const actual = [
    transactionLogs.includes(message),
    transactionLogs.includes(Alice),
    transactionLogs.includes(Bob),
  ];
  const expected = [true, true, true];

  expect(actual).toEqual(expected);
});

---

Trade-offs between 1 and 2

Solution 2 works already (except for a bug that malformats addresses in logs).

Solution 1 would be more clean and doesn't need extensive knowledge of your testing framework. However, it would require additional dev work to implement. It would also make debugging easier.

(Optional): Context

I'm writing tests for a project to get familiar with Flow. In the future these tests will assert program correctness.