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prachigauriarPrachi Gauriar
prachigauriar
and
Prachi Gauriar
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Add variable registration to ConfigVariableReader (#9)
 - Add RegisteredConfigVariable, a struct that captures a variable's key, default content, secrecy, and metadata for storage in homogeneous collections - Add encode closure to ConfigVariableContent for converting values back to ConfigContent, enabling default value encoding at registration time - Add encodeToContent on CodableValueRepresentation for converting encoded Data into the appropriate ConfigContent - Add ConfigVariableReader.register, which encodes and stores a variable's registration with duplicate-key detection and logging - Split ConfigVariableReaderTests into per-concern test files: scalar, array, raw representable, config expression, data representation, codable, and registration - Extract shared test mocks and metadata keys into Testing Support Co-authored-by: Prachi Gauriar <prachi@gauriar.com>
1 parent 7b4b0c4 commit e4cc18f

25 files changed

+3045
-2064
lines changed

‎Sources/DevConfiguration/Core/CodableValueRepresentation.swift‎

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@@ -118,6 +118,28 @@ public struct CodableValueRepresentation: Sendable {
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}
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/// Converts encoded `Data` into the appropriate ``ConfigContent`` for this representation.
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///
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/// For string-backed representations, this converts the data to a string using the representation's encoding and
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/// returns it as ``ConfigContent/string(_:)``. For data-backed representations, this returns the data's bytes as
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/// ``ConfigContent/bytes(_:)``.
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///
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/// - Parameter data: The encoded data to convert.
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/// - Returns: The ``ConfigContent`` representing the encoded data.
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/// - Throws: ``StringEncodingError`` if the data cannot be converted to a string using the expected encoding.
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func encodeToContent(_ data: Data) throws -> ConfigContent {
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switch kind {
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case .string(let encoding):
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guard let string = String(data: data, encoding: encoding) else {
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throw StringEncodingError(encoding: encoding)
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}
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return .string(string)
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case .data:
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return .bytes(Array(data))
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}
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}
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/// Watches for raw data changes from the reader based on this representation.
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///
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/// Each time the underlying configuration value changes, `onUpdate` is called with the new raw data (or `nil` if the
@@ -154,3 +176,10 @@ public struct CodableValueRepresentation: Sendable {
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}
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}
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}
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/// An error thrown when encoded data cannot be converted to a string using the expected encoding.
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struct StringEncodingError: Error {
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/// The string encoding that failed.
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let encoding: String.Encoding
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}

‎Sources/DevConfiguration/Core/ConfigVariableContent.swift‎

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@@ -65,6 +65,9 @@ public struct ConfigVariableContent<Value>: Sendable where Value: Sendable {
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_ line: UInt,
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_ continuation: AsyncStream<Value>.Continuation
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) async throws -> Void
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/// Encodes a value into a ``ConfigContent`` for registration.
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let encode: @Sendable (_ value: Value) throws -> ConfigContent
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}
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@@ -99,7 +102,8 @@ extension ConfigVariableContent where Value == Bool {
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .bool($0) }
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)
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}
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}
@@ -134,7 +138,8 @@ extension ConfigVariableContent where Value == [Bool] {
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .boolArray($0) }
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)
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}
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}
@@ -169,7 +174,8 @@ extension ConfigVariableContent where Value == Float64 {
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .double($0) }
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)
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}
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}
@@ -204,7 +210,8 @@ extension ConfigVariableContent where Value == [Float64] {
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .doubleArray($0) }
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)
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}
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}
@@ -239,7 +246,8 @@ extension ConfigVariableContent where Value == Int {
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .int($0) }
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)
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}
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .intArray($0) }
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)
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}
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .string($0) }
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)
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}
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}
@@ -344,7 +354,8 @@ extension ConfigVariableContent where Value == [String] {
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .stringArray($0) }
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)
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}
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}
@@ -379,7 +390,8 @@ extension ConfigVariableContent where Value == [UInt8] {
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .bytes($0) }
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)
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}
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}
@@ -420,7 +432,8 @@ extension ConfigVariableContent where Value == [[UInt8]] {
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .byteChunkArray($0) }
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)
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}
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .string($0.rawValue) }
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)
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .stringArray($0.map(\.rawValue)) }
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)
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .string($0.description) }
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)
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .stringArray($0.map(\.description)) }
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)
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}
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .int($0.rawValue) }
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)
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .intArray($0.map(\.rawValue)) }
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)
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .int($0.configInt) }
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)
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}
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continuation.yield(value)
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}
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}
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}
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},
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encode: { .intArray($0.map(\.configInt)) }
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)
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}
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}
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}
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continuation.yield(defaultValue)
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}
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},
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encode: { (value) in
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let resolvedEncoder = encoder ?? JSONEncoder()
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let data = try resolvedEncoder.encode(value)
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return try representation.encodeToContent(data)
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}
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)
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}

‎Sources/DevConfiguration/Core/ConfigVariableReader.swift‎

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@@ -7,6 +7,7 @@
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import Configuration
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import DevFoundation
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import OSLog
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/// Provides access to configuration values queried by a `ConfigVariable`.
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///
@@ -53,6 +54,12 @@ public struct ConfigVariableReader {
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/// The event bus used to post diagnostic events like ``ConfigVariableDecodingFailedEvent``.
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public let eventBus: EventBus
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/// The variables that have been registered with this reader, keyed by their configuration key.
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private(set) var registeredVariables: [ConfigKey: RegisteredConfigVariable] = [:]
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/// The logger used for registration diagnostics.
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private static let logger = Logger(subsystem: "DevConfiguration", category: "ConfigVariableReader")
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/// Creates a new `ConfigVariableReader` with the specified providers and the default telemetry access reporter.
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///
@@ -87,6 +94,44 @@ public struct ConfigVariableReader {
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}
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// MARK: - Registration
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extension ConfigVariableReader {
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/// Registers a configuration variable with this reader.
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///
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/// Registration records the variable's key, default value, secrecy, and metadata in a non-generic form so that the
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/// reader can provide information about all registered variables without needing their generic type parameters.
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///
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/// Registration is intended to be performed during setup, before the reader is shared with other components. If a
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/// variable with the same key has already been registered, the new registration overwrites the previous one, a
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/// warning is logged, and an assertion failure is triggered.
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///
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/// - Parameter variable: The configuration variable to register.
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public mutating func register<Value>(_ variable: ConfigVariable<Value>) {
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let defaultContent: ConfigContent
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do {
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defaultContent = try variable.content.encode(variable.defaultValue)
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} catch {
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assertionFailure("Failed to encode default value for config variable '\(variable.key)': \(error)")
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Self.logger.error("Failed to encode default value for config variable '\(variable.key)': \(error)")
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return
118+
}
119+
120+
if registeredVariables[variable.key] != nil {
121+
assertionFailure("Config variable '\(variable.key)' is already registered")
122+
Self.logger.error("Config variable '\(variable.key)' is already registered; overwriting")
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}
124+
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registeredVariables[variable.key] = RegisteredConfigVariable(
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key: variable.key,
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defaultContent: defaultContent,
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secrecy: variable.secrecy,
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metadata: variable.metadata
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)
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}
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}
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// MARK: - Value Access
91136

92137
extension ConfigVariableReader {

‎Sources/DevConfiguration/Core/RegisteredConfigVariable.swift‎

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@@ -0,0 +1,42 @@
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//
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// RegisteredConfigVariable.swift
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// DevConfiguration
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//
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// Created by Prachi Gauriar on 3/5/2026.
6+
//
7+
8+
import Configuration
9+
10+
/// A non-generic representation of a registered ``ConfigVariable``.
11+
///
12+
/// `RegisteredConfigVariable` stores the type-erased information from a ``ConfigVariable`` so that registered variables
13+
/// can be stored in homogeneous collections. It captures the variable's key, its default value as a ``ConfigContent``,
14+
/// its secrecy setting, and any attached metadata.
15+
@dynamicMemberLookup
16+
struct RegisteredConfigVariable: Sendable {
17+
/// The configuration key used to look up this variable's value.
18+
let key: ConfigKey
19+
20+
/// The variable's default value represented as a ``ConfigContent``.
21+
let defaultContent: ConfigContent
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23+
/// Whether this value should be treated as a secret.
24+
let secrecy: ConfigVariableSecrecy
25+
26+
/// The configuration variable's metadata.
27+
let metadata: ConfigVariableMetadata
28+
29+
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/// Provides dynamic member lookup access to metadata properties.
31+
///
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/// This subscript enables dot-syntax access to metadata properties, mirroring the access pattern on
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/// ``ConfigVariable``.
34+
///
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/// - Parameter keyPath: A keypath to a property on `ConfigVariableMetadata`.
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/// - Returns: The value of the metadata property.
37+
subscript<MetadataValue>(
38+
dynamicMember keyPath: KeyPath<ConfigVariableMetadata, MetadataValue>
39+
) -> MetadataValue {
40+
metadata[keyPath: keyPath]
41+
}
42+
}

‎Tests/DevConfigurationTests/Testing Support/MockCodableConfig.swift‎

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//
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// MockCodableConfig.swift
3+
// DevConfiguration
4+
//
5+
// Created by Prachi Gauriar on 3/5/2026.
6+
//
7+
8+
struct MockCodableConfig: Codable, Hashable, Sendable {
9+
let variant: String
10+
let count: Int
11+
}

‎Tests/DevConfigurationTests/Testing Support/MockConfigIntValue.swift‎

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//
2+
// MockConfigIntValue.swift
3+
// DevConfiguration
4+
//
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// Created by Prachi Gauriar on 3/5/2026.
6+
//
7+
8+
import Configuration
9+
10+
struct MockConfigIntValue: ExpressibleByConfigInt, Hashable, Sendable {
11+
let intValue: Int
12+
var configInt: Int { intValue }
13+
var description: String { "\(intValue)" }
14+
15+
init?(configInt: Int) {
16+
self.intValue = configInt
17+
}
18+
}

‎Tests/DevConfigurationTests/Testing Support/MockConfigStringValue.swift‎

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1+
//
2+
// MockConfigStringValue.swift
3+
// DevConfiguration
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//
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// Created by Prachi Gauriar on 3/5/2026.
6+
//
7+
8+
import Configuration
9+
10+
struct MockConfigStringValue: ExpressibleByConfigString, Hashable, Sendable {
11+
let stringValue: String
12+
var description: String { stringValue }
13+
14+
init?(configString: String) {
15+
self.stringValue = configString
16+
}
17+
}

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