Add Key coding strategy

[norio-nomura]

It is a rewrite of #92.

API Changes

YAMLEncoder

• Add KeyEncodingStrategy with cases: useDefaultKeys, convertToSnakeCase and custom(_:)
• Copy Options from Emitter with adding keyEncodingStrategy

YAMLDecoder

• Add KeyDecodingStrategy with cases: useDefaultKeys, useSnakeCasedKeys, useCustomizedKeys(_:) and custom(_:)
• Add Options having keyDecodingStrategy
• Change behaviors of allKeys:
  • Do not include duplicate keys
  • The order of the keys is no longer the same as in YAML

Difference between JSONEncoder and YAMLEncoder of KeyEncodingStrategy

The behavior is compatible with JSONEncoder. KeyEncodingStrategy

Difference between JSONDecoder and YAMLDecoder of KeyDecodingStrategy

• Drop convertFromSnakeCase, because that has a problem: SR-6629
• Add useSnakeCasedKeys
  That uses snake cased CodingKeys for accessing YAML contents.
  same with Add useSnakeCasedKeys to JSONDecoder.KeyDecodingStrategy swiftlang/swift#14039
  This replaces convertFromSnakeCase.
• Add useCustomizedKeys((_ codingPath: [CodingKey]) -> CodingKey)
  That uses custom converted CodingKeys for accessing YAML contents.
• custom((_ codingPath: [CodingKey]) -> CodingKey) is compatible with JSONDecoder's one

[doofyus]

Hi, what's the status with this one and can i be of help in moving it forward?
(KeyDecodingStrategy seems like an essential part, as Swift is commonly written in camelCase vs yaml usually in snake_case)

[beijingrice]

I view the webpage of WWDC2019, and found it’s lib on Github. Is that you found me by Github? My English maybe gets some error. :-)

[beijingrice]

But I think that’s very good because everyone can link this lib to them’s Xcode project and that my our coding more easy.

[frugoman]

Why was this closed? what's needed for this to be reopened and added to the lib? it's pretty essential

[jpsim]

This is definitely something I'd like to see, not sure where @norio-nomura left it off. CI was failing but it seems that Microsoft Azure Pipelines hasn't kept the results from these runs.