null/~/NULL/Null parsed as strings, not nil

[finestructure]

null/~/NULL/Null parsed as strings, not nil

[norio-nomura]

Thanks for reporting! This is a bug in YAMLDecoder.
I opened #158 that fixes this issue.

[finestructure]

PS: For reference, this passes:

    func test_null_json() throws {
        let d = """
            {
                "n1": null,
            }
            """.data(using: .utf8)!
        struct Test: Decodable {
            let n1: String?
        }
        let t = try JSONDecoder().decode(Test.self, from: d)
        XCTAssertNil(t.n1)
    }

[norio-nomura]

side note:
YAMLDecoder does not use Resolver and calls construct(from:) directly for each type.
In addition, decodeNil() uses Node.null that calls NSNull.construct(from:).
https://github.com/jpsim/Yams/blob/master/Sources/Yams/Decoder.swift#L223