Encode/Decode SemanticVersion as a single value string

Since SemanticVersion is LosslessStringConvertible, it seems to make more sense for its encoding/decoding strategy to use that to allow it to be serialized more succinctly as a single string value, rather than using the synthesized structured encoding provided by simply declaring Codable conformance. This is also more likely to conform to how such values will be served up by APIs.

This change implements custom init(from:) and encode(to:) methods to provide this behavior, as well as unit tests to verify the behavior.

Note this *is* a breaking change to the encoded format of the structure.

Sources/SemanticVersion/SemanticVersion.swift

@@ -22,7 +22,7 @@ import Foundation
 /// 2. MINOR version when you add functionality in a backwards compatible manner, and
 /// PATCH version when you make backwards compatible bug fixes.
 /// Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.
-public struct SemanticVersion: Codable, Equatable, Hashable {
+public struct SemanticVersion: Equatable, Hashable {
     public var major: Int
     public var minor: Int
     public var patch: Int
@@ -50,6 +50,25 @@ public struct SemanticVersion: Codable, Equatable, Hashable {
     }
 }
 
+extension SemanticVersion: Codable {
+    public init(from decoder: Decoder) throws {
+        let container = try decoder.singleValueContainer()
+        guard let version = SemanticVersion(try container.decode(String.self)) else {
+            throw DecodingError.dataCorrupted(
+                DecodingError.Context(
+                    codingPath: container.codingPath,
+                    debugDescription: "Expected valid semver 2.0 string"
+                )
+            )
+        }
+        self = version
+    }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.singleValueContainer()
+        try container.encode(description)
+    }
+}
 
 extension SemanticVersion: LosslessStringConvertible {
 

Tests/SemanticVersionTests/SemanticVersionTests.swift

@@ -179,4 +179,58 @@ final class SemanticVersionTests: XCTestCase {
         XCTAssertFalse(SemanticVersion(0, 0, 0).isPatchRelease)
     }
 
+    func test_encodable() throws {
+        let encoder = JSONEncoder()
+        var actual: String
+
+        actual = String(data: try encoder.encode(SemanticVersion(1, 2, 3)), encoding: .utf8)!
+        XCTAssertEqual(actual, #""1.2.3""#)
+
+        actual = String(data: try encoder.encode(SemanticVersion(3, 2, 1, "alpha.4")), encoding: .utf8)!
+        XCTAssertEqual(actual, #""3.2.1-alpha.4""#)
+
+        actual = String(data: try encoder.encode(SemanticVersion(3, 2, 1, "", "build.42")), encoding: .utf8)!
+        XCTAssertEqual(actual, #""3.2.1+build.42""#)
+
+        actual = String(data: try encoder.encode(SemanticVersion(7, 7, 7, "beta.423", "build.17")), encoding: .utf8)!
+        XCTAssertEqual(actual, #""7.7.7-beta.423+build.17""#)
+    }
+
+    func test_decodable() throws {
+        let decoder = JSONDecoder()
+        var json: Data
+
+        json = #""1.2.3-a.4+42.7""#.data(using: .utf8)!
+        XCTAssertEqual(
+            try decoder.decode(SemanticVersion.self, from: json),
+            SemanticVersion(1, 2, 3, "a.4", "42.7")
+        )
+
+        json = #"["1.2.3-a.4+42.7", "7.7.7"]"#.data(using: .utf8)!
+        XCTAssertEqual(
+            try decoder.decode([SemanticVersion].self, from: json),
+            [SemanticVersion(1, 2, 3, "a.4", "42.7"), SemanticVersion(7, 7, 7)]
+        )
+
+        struct Foo: Decodable, Equatable {
+            let v: SemanticVersion
+        }
+
+        json = #"{"v": "1.2.3-a.4+42.7"}"#.data(using: .utf8)!
+        XCTAssertEqual(
+            try decoder.decode(Foo.self, from: json),
+            Foo(v: SemanticVersion(1, 2, 3, "a.4", "42.7"))
+        )
+
+        json = #"{"v": "I AM NOT A SEMVER"}"#.data(using: .utf8)!
+        XCTAssertThrowsError(_ = try decoder.decode(Foo.self, from: json)) { error in
+            switch error as? DecodingError {
+            case .dataCorrupted(let context):
+                XCTAssertEqual(context.codingPath.map(\.stringValue), ["v"])
+                XCTAssertEqual(context.debugDescription, "Expected valid semver 2.0 string")
+            default:
+                XCTFail("Expected DecodingError.dataCorrupted, got \(error)")
+            }
+        }
+    }
 }