Pretty-printed intrinsic-value elements are split across multiple lines

[weppos]

When an element stores its text content via the empty-string CodingKey (""), XMLEncoder pretty printing splits the intrinsic value onto its own line instead of keeping the element inline.

Minimal example:

struct Measurement: Codable {
    @Attribute var ref: String?
    var value: Double

    enum CodingKeys: String, CodingKey {
        case ref
        case value = ""
    }
}

let encoder = XMLEncoder()
encoder.outputFormatting = [.prettyPrinted]
encoder.prettyPrintIndentation = .spaces(4)

Actual output:

<measurement ref="sensor-1">
    120000.0
</measurement>

Expected output:

<measurement ref="sensor-1">120000.0</measurement>

This also affects the same intrinsic-value shape when the element has no attributes.