feature: Add Weaver[Any] support for Map[String, Any] serialization

[xerial]

Summary

• Add AnyWeaver to support serialization of generic collections like Map[String, Any] and Seq[Any]
• Support knownWeavers parameter for registering custom type weavers (similar to airframe-codec's knownSurfaces)
• Runtime type matching for primitives, collections, and Scala 3 enums
• Falls back to toString for unknown types

Usage Example

case class Person(name: String, age: Int)

val anyWeaver = AnyWeaver(
  knownWeavers = Map(classOf[Person] -> Weaver.derived[Person])
)

val data: Map[String, Any] = Map(
  "user" -> Person("Alice", 30),
  "count" -> 42
)
val msgpack = anyWeaver.weave(data)

Test plan

• Map[String, Any] with primitives (roundtrip)
• JSON serialization of Map[String, Any]
• Nested Map[String, Any] with inner maps and lists
• Seq[Any] with mixed types
• null values and Option[Any]
• Scala 3 enum serialization
• Array[Any] and Array[Byte] handling
• knownWeavers with custom case class

🤖 Generated with Claude Code

[gemini-code-assist]

Summary of Changes

Hello @xerial, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the uni-weaver library by introducing an AnyWeaver component, which provides a flexible and powerful mechanism for serializing and deserializing heterogeneous Scala data structures. The primary goal is to enable seamless handling of generic collections like Map[String, Any] and Seq[Any] by performing runtime type matching for common types, supporting custom type serializers through knownWeavers, and ensuring a consistent fallback for unhandled types. This improvement makes the library more adaptable for working with dynamically typed data, mirroring the functionality found in similar serialization frameworks.

Highlights

• New AnyWeaver Implementation: Introduced a new AnyWeaver component to support serialization and deserialization of Any types, enabling flexible handling of heterogeneous data structures.
• Generic Collection Support: Added robust support for serializing generic collections such as Map[String, Any] and Seq[Any], which can contain values of various types.
• Custom Type Registration: Implemented a knownWeavers parameter, allowing users to register custom Weaver instances for specific types, ensuring proper serialization of domain-specific objects.
• Runtime Type Matching and Fallback: The AnyWeaver performs runtime type matching for primitives, collections, and Scala 3 enums, with a graceful fallback to toString serialization for unknown types.
• Comprehensive Test Coverage: A new test suite (AnyWeaverTest) has been added, covering a wide range of scenarios including nested collections, null handling, enum serialization, and custom type integration.

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[gemini-code-assist]

Code Review

This pull request introduces AnyWeaver for serializing generic collections like Map[String, Any], which is a great addition. The implementation is comprehensive, covering primitives, collections, and custom types via knownWeavers. The test suite is also thorough and covers many edge cases.

I've found one high-severity bug in the error handling logic within AnyWeaverImpl's unpackMap method, which could lead to errors when unpacking malformed map data. I've also left a minor comment on the design document to improve its reusability for other developers.

Overall, this is a solid feature implementation. Once the identified issue is addressed, it should be ready for merging.

[gemini-code-assist]

There's a bug in the error handling logic when unpacking a map key. If unpack(u, keyContext) fails, the unpacker's position will be at the corresponding value of the failed key. The current loop while i < len do ... attempts to skip len - i full key-value pairs. This is one value too many and will likely cause an error by reading past the end of the map.

The logic should be to first skip the value of the current failed pair, and then skip the remaining full pairs.

          u.skipValue // Skip value of the current pair
          i += 1
          while i < len do
            u.skipValue // key
            u.skipValue // value
            i += 1

[gemini-code-assist]

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