// /tmp/test_decode.swift
import Foundation

// アプリと同じモデル定義をコピー
struct MyModel: Codable { /* ... */ }
struct Container: Codable { let items: [MyModel] }

do {
    let url = URL(fileURLWithPath: "path/to/data.json")
    let data = try Data(contentsOf: url)
    let container = try JSONDecoder().decode(Container.self, from: data)
    print("SUCCESS: \(container.items.count) items")
} catch let error as DecodingError {
    switch error {
    case .keyNotFound(let key, let context):
        print("KEY NOT FOUND: \(key.stringValue)")
        print("Path: \(context.codingPath.map { $0.stringValue })")
    case .typeMismatch(let type, let context):
        print("TYPE MISMATCH: expected \(type)")
        print("Path: \(context.codingPath.map { $0.stringValue })")
    case .valueNotFound(let type, let context):
        print("VALUE NOT FOUND: \(type)")
        print("Path: \(context.codingPath.map { $0.stringValue })")
    case .dataCorrupted(let context):
        print("DATA CORRUPTED: \(context.debugDescription)")
    @unknown default:
        print("Unknown: \(error)")
    }
} catch {
    print("ERROR: \(error)")
}

cd /path/to/project && swift /tmp/test_decode.swift