"New Codable" prototype available for feedback

[tera]

@kperryua

// Written code:
@JSONCodable
struct BlogPost {
    ...
    @CodingDefault([])
    let tags: [String]
}

Could this use the default value provided normally? var tags: [String] = []

BTW, do you plan to have an ability to opt-out some fields from being encodable/decodable?
Either on a per field manner or, on a per type manner.

@kperryua

// Synthesized code:
extension BlogPost: JSONEncodable {
    func encode(to encoder: inout JSONEncoder2) throws -> Person {
        try encoder.encodeStructFields() { fieldEncoder in
            try fieldEncoder.encode(field: CodingFields.title, value: self.title)
            try fieldEncoder.encode(field: CodingFields.subtitle, value: self.subtitle)
            let publishDateValue = self.publishDate.formatted(.iso8601)
            try fieldEncoder.encode(field: CodingFields.publishDate, value: publishDateValue)
            try fieldEncoder.encode(field: CodingFields.body, value: self.body)
            let tagsValue = self.tags ?? []
            try fieldEncoder.encode(field: CodingFields.tags, value: tagsValue)
        }
    }
}

I wonder if this could be more generic like this (pseudocode):

    // generic
    func encode(to encoder: inout JSONEncoder2) throws -> T {
        try encoder.encodeStructFields() { fieldEncoder in
           fieldEncoder.allFields { field in
              try fieldEncoder.encode(field: field.title, value: field.value)
           }
        }
    }

in which case having this per-type might be not required. Similarly for decoding.

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I like the desire, but maybe we could invest into a more complete, robust and performant mirror machinery first... and reimplement new codable on top of that.