RUMM-437 Encoding doesn't ignore miliseconds anymore

[buranmert]

Closes #95

What and why?

SDK collects Logs and writes them onto disk, then uploads them as raw data
It relies on JSONEncoder with dateEncodingStrategy = .iso8601
However, it turns out IS08601 doesn't enforce miliseconds and JSONEncoder omits them

let date = {2020-05-04T18:19:57.109Z}
jsonEncoder.dateEncodingStrategy = .iso8601
jsonEncoder.encode(date) // becomes {2020-05-04T18:19:57Z}

The result is very well described in the original issue #95

How?

There are 2 main solutions:

ISO8601DateFormatter and dateEncodingStrategy = .custom

🍎 Apple recommends using ISO8601DateFormatter when dealing with ISO8601 format.
❌ However, that enforces us to use dateEncodingStrategy = .custom
Because the logical strategy option, .formatted(DateFormatter), doesn't accept it as it's not a subclass of DateFormatter

Customized DateFormatter and dateEncodingStrategy = .formatted

Although this is not the official way, this method is used in many places/projects.

Basically, we describe the ISO8601 standard in our own DateFormatter instance
Then we pass the instance to dateEncodingStrategy = .formatted(dateFormatter)
✅ Now we have miliseconds in the encoded data

UPDATE:

I turned to the first option: ISO8601DateFormatter and dateEncodingStrategy = .custom

Questions?

How can we test encoding without making types Decodable, since they don't need to be decoded in the main target?

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference

[ncreated]

let date = {2020-05-04T18:19:57.109Z}
jsonEncoder.dateEncodingStrategy = .iso8601
jsonEncoder.encode(date) // becomes {2020-05-04T18:19:57Z}

That's super interesting 👌. Is this factorial precision lost somewhere documented by Apple?

How can we test encoding without making types Decodable, since they don't need to be decoded in the main target?

We should unit test the iso8601Formatter by its own and just assert that the encoded String includes factorial seconds:

func testEncodingDateWithISO8601FullFormat() throws {
    let jsonEncoder = JSONEncoder()
    jsonEncoder.dateEncodingStrategy = .formatted(iso8601Formatter)

    let knownDate: Date = .mockDecember15th2019At10AMUTC(addingTimeInterval: 0.123)
    let encodedKnownDate = try jsonEncoder.encode(knownDate)

    let jsonDecoder = JSONDecoder()
    let knownDateDecodedString = try jsonDecoder.decode(String.self, from: encodedKnownDate)

    XCTAssertEqual(knownDateDecodedString, "2019-12-15T10:00:00.123")
}

Higher-level tests should just work, because:

• we only have a few precisely picked unit tests which assert the date format - with LoggerTests.testSendingMinimalLogWithDefaultLogger() being the most crucial one;
• they work against .mockDecember15th2019At10AMUTC() mock, which doesn't include factorial seconds.

[buranmert]

@ncreated I was thinking of a more complete encoding testing strategy (not only Dates) but I couldn't come up with any idea
I guess the test case that you suggested should be fine 👌

[ncreated]

✨ 🚀