🧩 ErrorInfo

A Swift-native, type-safe and concurrency-compliant alternative to [String: Any] for storing structured error details.

(currently is prepared for release 0.1.0)

🚀 Why ErrorInfo?

While Swift has robust support for modeling errors through the Error protocol, the language lacks a native, structured, and thread-safe way to store additional error context.

In practice, [String: Any] is often used for this, but this pattern suffers from serious drawbacks:

• ❌ Not compatible with modern concurrency – can't be safely used across concurrent contexts
• ❌ Unsafe typing – Any allows placing arbitrary, non-type-safe values
• ❌ Loss of previous values – inserting a value for an existing key overwrites the old one
• ❌ Poor merging support – key collisions can lead to data loss
• ❌ Debugging complexity – lacks built-in ordering or tracing mechanisms

✅ ErrorInfo

The ErrorInfo library introduces a family of structured, type-safe, and Sendable error info containers that:

• Provide checking values for safety at compile time
• Support advanced merge strategies to avoid data loss
• Are compatible with Swift concurrency
• Provide ordered and unordered variants
• Allow merging, tracing, and resolving conflicts intelligently

⚠️ Design Principles

• ✅ Safe merging without data loss
• ✅ Trackable value origins for logging & debugging
• ✅ No implicit value overwrites
• ✅ Type-safe values only

📦 Library Overview

Provided Types

Feature	ErrorInfo	LegacyErrorInfo	[String: Any]
Collision Resolution	✅ Yes (store all values)	☑️ Yes (key augmentation)	❌ No
Prevent implicit overwrite	✅ No	✅ No	❌ Yes
Prevent equal values	✅ Yes	✅ Yes	－
Preserve nil values	✅ Yes	✅ Yes	❌ No
Collision source	✅ Yes	✅ Yes	❌ No
Type info	✅ Yes	✅ Yes	❌ No
Merge	✅ Yes	☑️ Yes	💥 Data loss
Key transform	✅ Yes	☑️ Yes	💥 Data loss
Sendable	✅ Yes	❌ No	❌ No
Ordered	Yes	No	No
Type of Value	any ErrorInfoValueType	Any	Any

*any ErrorInfoValueType is typeaias to Sendable & Equatable & CustomStringConvertible

This constraint ensures:

• ✅ Thread Safety via Sendable
• ✅ Meaningful Logging via CustomStringConvertible
• ✅ Collision Detection via Equatable

🧠 Design Highlights

🔁 Merging with Collision Resolution The library supports two collision resolution strategies:

• Multiple Values per Key – preserve all values
• Key Augmentation – append suffixes (e.g., error domain, code) to conflicting keys

Example:

let e1: ErrorInfo = ["key": 1]
let e2: ErrorInfo = ["key": "A"]
let merged = e1.merged(with: e2)

// result: [1, "A"]
let allValues = merged.allValues(forKey: "key")

Or with key augmentation: TBD

🧩 Example: value collisions, no implicit overwrite, prevent equal values, preserve nil values

Unlike dictionaries, ErrorInfo keeps all values.

var info: ErrorInfo = ["a": 1]
info["a"] = 1                     // ❌ Skipped (duplicate)
info["a"] = 2                     // ✅ Added (another value)
info["a"] = "2"                   // ✅ Added (different type)
info["a"] = nil Optional<Decimal> // ✅ Added (nil value)

info.appendIfNotNil(3 as Optional,
                    forKey: "a")  // ✅ added (non-nil another value)

allValues(forKey: "a")             // 1, 2, "2", 3
allValuesWithMetaInfo(forKey: "a") // 1, 2, "2", nil, 3

🧪 Example Use Case

Merging Multiple Errors TBD

🔐 Non-Sendable & AnyObject Storage Storing non-Sendable or AnyObject values is explicitly not supported in ErrorInfo. If needed, use a separate, opt-in container like TransferableStorage (prototype available in [Sources]).

📦 Installation .package(url: "https://github.com/iDmitriyy/ErrorInfo", branch: "main")

🧪 Tests (TBD after api surface become stable) All collision detection, value comparison, and merge behaviors are covered in unit tests.

📣 Contributing Contributions are welcome! If you have ideas, optimizations, or find a bug — feel free to open an issue or submit a PR.

ErrorInfo details