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[WIP] Add Key coding strategy #92

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[WIP] Add Key coding strategy #92

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51 changes: 44 additions & 7 deletions Sources/Yams/Decoder.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -9,13 +9,14 @@
import Foundation

public class YAMLDecoder {
public var options = Options()
public init() {}
public func decode<T>(_ type: T.Type = T.self,
from yaml: String,
userInfo: [CodingUserInfoKey: Any] = [:]) throws -> T where T: Swift.Decodable {
do {
let node = try Yams.compose(yaml: yaml, .basic) ?? ""
let decoder = _Decoder(referencing: node, userInfo: userInfo)
let decoder = _Decoder(referencing: node, options: options, userInfo: userInfo)
let container = try decoder.singleValueContainer()
return try container.decode(T.self)
} catch let error as DecodingError {
Expand All @@ -26,14 +27,39 @@ public class YAMLDecoder {
underlyingError: error))
}
}

public struct Options {
/// The strategy to use for decoding keys. Defaults to `.useDefaultKeys`.
public var keyDecodingStrategy: KeyDecodingStrategy = .useDefaultKeys
}

/// The strategy to use for automatically changing the value of keys before decoding.
public enum KeyDecodingStrategy {
/// Use the keys specified by each type. This is the default strategy.
case useDefaultKeys

/// Convert from "snake_case_keys" to "camelCaseKeys" before attempting to match a key with the one specified
/// by each type.
case convertFromSnakeCase

/// Provide a custom conversion from the key in the encoded JSON to the keys specified by the decoded types.
/// The full path to the current decoding position is provided for context (in case you need to locate this
/// key within the payload). The returned key is used in place of the last component in the coding path before
/// decoding.
/// If the result of the conversion is a duplicate key, then only one value will be present in the container
/// for the type to decode from.
case custom((_ codingPath: [CodingKey]) -> CodingKey)
}
}

struct _Decoder: Decoder { // swiftlint:disable:this type_name

fileprivate let node: Node
typealias Options = YAMLDecoder.Options
var options: Options

init(referencing node: Node, userInfo: [CodingUserInfoKey: Any], codingPath: [CodingKey] = []) {
init(referencing node: Node, options: Options, userInfo: [CodingUserInfoKey: Any], codingPath: [CodingKey] = []) {
self.node = node
self.options = options
self.userInfo = userInfo
self.codingPath = codingPath
}
Expand Down Expand Up @@ -69,9 +95,19 @@ struct _Decoder: Decoder { // swiftlint:disable:this type_name
return constructed
}


/// Returns `String` applied `KeyDecodingStrategy`
fileprivate func convert(_ key: CodingKey) -> String {
switch options.keyDecodingStrategy {
case .useDefaultKeys: return key.stringValue
case .convertFromSnakeCase: return key.stringValue.snakecased
case let .custom(converter): return converter(codingPath + [key]).stringValue
}
}

/// create a new `_Decoder` instance referencing `node` as `key` inheriting `userInfo`
fileprivate func decoder(referencing node: Node, `as` key: CodingKey) -> _Decoder {
return .init(referencing: node, userInfo: userInfo, codingPath: codingPath + [key])
return .init(referencing: node, options: options, userInfo: userInfo, codingPath: codingPath + [key])
}
}

Expand All @@ -92,7 +128,7 @@ struct _KeyedDecodingContainer<K: CodingKey> : KeyedDecodingContainerProtocol {

var codingPath: [CodingKey] { return decoder.codingPath }
var allKeys: [Key] { return mapping.keys.flatMap { $0.string.flatMap(Key.init(stringValue:)) } }
func contains(_ key: Key) -> Bool { return mapping[key.stringValue] != nil }
func contains(_ key: Key) -> Bool { return mapping[decoder.convert(key)] != nil }

func decodeNil(forKey key: Key) throws -> Bool {
return try node(for: key) == Node("null", Tag(.null))
Expand Down Expand Up @@ -132,8 +168,9 @@ struct _KeyedDecodingContainer<K: CodingKey> : KeyedDecodingContainerProtocol {
// MARK: -

private func node(for key: CodingKey) throws -> Node {
guard let node = mapping[key.stringValue] else {
throw _keyNotFound(at: codingPath, key, "No value associated with key \(key) (\"\(key.stringValue)\").")
let convertedKey = decoder.convert(key)
guard let node = mapping[convertedKey] else {
throw _keyNotFound(at: codingPath, key, "No value associated with key \(key) (\"\(convertedKey)\").")
}
return node
}
Expand Down
95 changes: 86 additions & 9 deletions Sources/Yams/Encoder.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -9,15 +9,14 @@
import Foundation

public class YAMLEncoder {
public typealias Options = Emitter.Options
public var options = Options()
public init() {}
public func encode<T: Swift.Encodable>(_ value: T, userInfo: [CodingUserInfoKey: Any] = [:]) throws -> String {
do {
let encoder = _Encoder(userInfo: userInfo)
let encoder = _Encoder(options: options, userInfo: userInfo)
var container = encoder.singleValueContainer()
try container.encode(value)
return try serialize(node: encoder.node, options: options)
return try serialize(node: encoder.node, options: options.emitterOptions)
} catch let error as EncodingError {
throw error
} catch {
Expand All @@ -28,12 +27,78 @@ public class YAMLEncoder {
throw EncodingError.invalidValue(value, context)
}
}

public struct Options {
/// Set if the output should be in the "canonical" format as in the YAML specification.
public var canonical: Bool = false
/// Set the intendation increment.
public var indent: Int = 0
/// Set the preferred line width. -1 means unlimited.
public var width: Int = 0
/// Set if unescaped non-ASCII characters are allowed.
public var allowUnicode: Bool = false
/// Set the preferred line break.
public var lineBreak: Emitter.LineBreak = .ln

// internal since we don't know if these should be exposed.
var explicitStart: Bool = false
var explicitEnd: Bool = false

/// The %YAML directive value or nil
public var version: (major: Int, minor: Int)?

/// Set if emitter should sort keys in lexicographic order.
public var sortKeys: Bool = false

/// The strategy to use for encoding keys. Defaults to `.useDefaultKeys`.
public var keyEncodingStrategy: KeyEncodingStrategy = .useDefaultKeys

fileprivate var emitterOptions: Emitter.Options {
return .init(canonical: canonical, indent: indent, width: width, allowUnicode: allowUnicode,
lineBreak: lineBreak, version: version, sortKeys: sortKeys)
}
}

/// The strategy to use for automatically changing the value of keys before encoding.
public enum KeyEncodingStrategy {
/// Use the keys specified by each type. This is the default strategy.
case useDefaultKeys

/// Convert from "camelCaseKeys" to "snake_case_keys" before writing a key to YAML payload.
case convertToSnakeCase

/// Provide a custom conversion to the key in the encoded YAML from the keys specified by the encoded types.
/// The full path to the current encoding position is provided for context (in case you need to locate this
/// key within the payload). The returned key is used in place of the last component in the coding path before
/// encoding.
/// If the result of the conversion is a duplicate key, then only one value will be present in the result.
case custom((_ codingPath: [CodingKey]) -> CodingKey)
}
}

extension YAMLEncoder.Options {
// initializer without exposing internal properties
public init(canonical: Bool = false, indent: Int = 0, width: Int = 0, allowUnicode: Bool = false,
lineBreak: Emitter.LineBreak = .ln, version: (major: Int, minor: Int)? = nil, sortKeys: Bool = false,
keyEncodingStrategy: YAMLEncoder.KeyEncodingStrategy = .useDefaultKeys) {
self.canonical = canonical
self.indent = indent
self.width = width
self.allowUnicode = allowUnicode
self.lineBreak = lineBreak
self.version = version
self.sortKeys = sortKeys
self.keyEncodingStrategy = keyEncodingStrategy
}
}

class _Encoder: Swift.Encoder { // swiftlint:disable:this type_name
var node: Node = .unused
typealias Options = YAMLEncoder.Options
let options: Options

init(userInfo: [CodingUserInfoKey: Any] = [:], codingPath: [CodingKey] = []) {
init(options: Options, userInfo: [CodingUserInfoKey: Any] = [:], codingPath: [CodingKey] = []) {
self.options = options
self.userInfo = userInfo
self.codingPath = codingPath
}
Expand Down Expand Up @@ -116,6 +181,15 @@ class _Encoder: Swift.Encoder { // swiftlint:disable:this type_name
}

fileprivate var canEncodeNewValue: Bool { return node == .unused }

/// Returns `String` applied `KeyEncodingStrategy`
fileprivate func convert(_ key: CodingKey) -> String {
switch options.keyEncodingStrategy {
case .useDefaultKeys: return key.stringValue
case .convertToSnakeCase: return key.stringValue.snakecased
case let .custom(converter): return converter(codingPath + [key]).stringValue
}
}
}

class _ReferencingEncoder: _Encoder { // swiftlint:disable:this type_name
Expand All @@ -126,14 +200,16 @@ class _ReferencingEncoder: _Encoder { // swiftlint:disable:this type_name

fileprivate init(referencing encoder: _Encoder, key: CodingKey) {
self.encoder = encoder
reference = .mapping(key.stringValue)
super.init(userInfo: encoder.userInfo, codingPath: encoder.codingPath + [key])
reference = .mapping(encoder.convert(key))
super.init(options: encoder.options, userInfo: encoder.userInfo, codingPath: encoder.codingPath + [key])
}

fileprivate init(referencing encoder: _Encoder, at index: Int) {
self.encoder = encoder
reference = .sequence(index)
super.init(userInfo: encoder.userInfo, codingPath: encoder.codingPath + [_YAMLCodingKey(index: index)])
super.init(options: encoder.options,
userInfo: encoder.userInfo,
codingPath: encoder.codingPath + [_YAMLCodingKey(index: index)])
}

deinit {
Expand All @@ -158,7 +234,7 @@ struct _KeyedEncodingContainer<K: CodingKey> : KeyedEncodingContainerProtocol {
// MARK: - Swift.KeyedEncodingContainerProtocol Methods

var codingPath: [CodingKey] { return encoder.codingPath }
func encodeNil(forKey key: Key) throws { encoder.mapping[key.stringValue] = .null }
func encodeNil(forKey key: Key) throws { encoder.mapping[encoder.convert(key)] = .null }
func encode(_ value: Bool, forKey key: Key) throws { try encoder(for: key).represent(value) }
func encode(_ value: Int, forKey key: Key) throws { try encoder(for: key).represent(value) }
func encode(_ value: Int8, forKey key: Key) throws { try encoder(for: key).represent(value) }
Expand All @@ -172,7 +248,7 @@ struct _KeyedEncodingContainer<K: CodingKey> : KeyedEncodingContainerProtocol {
func encode(_ value: UInt64, forKey key: Key) throws { try encoder(for: key).represent(value) }
func encode(_ value: Float, forKey key: Key) throws { try encoder(for: key).represent(value) }
func encode(_ value: Double, forKey key: Key) throws { try encoder(for: key).represent(value) }
func encode(_ value: String, forKey key: Key) throws { encoder.mapping[key.stringValue] = Node(value) }
func encode(_ value: String, forKey key: Key) throws { encoder.mapping[encoder.convert(key)] = Node(value) }
func encode<T>(_ value: T, forKey key: Key) throws where T: Encodable { try encoder(for: key).encode(value) }

func nestedContainer<NestedKey>(keyedBy type: NestedKey.Type,
Expand Down Expand Up @@ -339,3 +415,4 @@ private func serialize(node: Node, options: Emitter.Options) throws -> String {
version: options.version,
sortKeys: options.sortKeys)
}
// swiftlint:disable:this file_length
26 changes: 26 additions & 0 deletions Sources/Yams/String+Yams.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -91,4 +91,30 @@ extension String {
return self + "\n"
}
}

/// Returns snake cased string
/// - example: "myURLProperty".snakecased() == "my_url_property"
var snakecased: String {
guard !isEmpty else { return self }
var words = [Range<Index>](), wordStart = startIndex, searchStart = startIndex
while let upperCaseRange = rangeOfCharacter(from: .uppercaseLetters, range: searchStart..<endIndex) {
if upperCaseRange.lowerBound != startIndex {
words.append(wordStart..<upperCaseRange.lowerBound)
}
guard let lowerCaseRange = rangeOfCharacter(from: .lowercaseLetters,
range: upperCaseRange.upperBound..<endIndex) else {
wordStart = upperCaseRange.lowerBound
break
}
if upperCaseRange.upperBound == lowerCaseRange.lowerBound {
wordStart = upperCaseRange.lowerBound
} else {
wordStart = index(before: lowerCaseRange.lowerBound)
words.append(upperCaseRange.lowerBound..<wordStart)
}
searchStart = lowerCaseRange.upperBound
}
words.append(wordStart..<endIndex)
return words.map({ self[$0] }).joined(separator: "_").lowercased()
}
}
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