feat: Add metadata support to Part types

[ehsavoie]

Add optional metadata field to TextPart, FilePart, and DataPart records to support additional contextual information for message and artifact content parts as specified in the A2A protocol v1.0.

Changes:

• Add metadata parameter to Part constructors (TextPart, FilePart, DataPart)
• Update PartMapper to convert metadata between domain and gRPC proto
• Update JsonUtil PartTypeAdapter to serialize/deserialize metadata

Fixes #649 🦕

[gemini-code-assist]

Summary of Changes

Hello @ehsavoie, 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 enhances the A2A protocol implementation by adding support for an optional metadata field to TextPart, FilePart, and DataPart types. This change allows for richer contextual information to be associated with message and artifact content parts. The modifications span across domain object definitions, JSON serialization/deserialization logic, and gRPC mapping to ensure seamless integration and proper handling of this new field throughout the system.

Highlights

• Metadata Support for Part Types: Introduced an optional metadata field to TextPart, FilePart, and DataPart records, allowing for additional contextual information as specified in the A2A protocol v1.0.
• Serialization and Deserialization: Updated JsonUtil's PartTypeAdapter to correctly serialize and deserialize the new metadata field for all affected Part types, ensuring proper JSON representation.
• gRPC Mapping: Modified PartMapper to handle the conversion of the metadata field between the domain objects (TextPart, FilePart, DataPart) and their corresponding gRPC protocol buffer representations.
• Constructor and Builder Updates: Adjusted the constructors of TextPart, FilePart, and DataPart to accept the new optional metadata parameter. The DataPart.Builder was also updated to include a method for setting metadata.

Changelog

• jsonrpc-common/src/main/java/io/a2a/jsonrpc/common/json/JsonUtil.java
  • Imported java.util.Map and com.google.gson.reflect.TypeToken for metadata handling.
  • Modified PartTypeAdapter to serialize the metadata field for TextPart, FilePart, and DataPart.
  • Modified PartTypeAdapter to deserialize the metadata field for TextPart, FilePart, and DataPart.
  • Updated PartTypeAdapter's read method to allow metadata as an optional key in Part objects, adjusting key count validation.
• jsonrpc-common/src/test/java/io/a2a/jsonrpc/common/json/StreamingEventKindSerializationTest.java
  • Updated TextPart instantiations to include null for the new metadata parameter in test cases.
• jsonrpc-common/src/test/java/io/a2a/jsonrpc/common/json/TaskSerializationTest.java
  • Updated TextPart, FilePart, and DataPart instantiations to include null for the new metadata parameter in various test cases.
• pom.xml
  • Added version.testcontainers property to manage Testcontainers dependency version.
  • Added testcontainers-bom dependency with import scope to the dependency management section.
• spec-grpc/src/main/java/io/a2a/grpc/mapper/PartMapper.java
  • Modified toProto method to map the metadata field from TextPart, FilePart, and DataPart to their gRPC protocol buffer representations.
  • Modified fromProto method to map the metadata field from gRPC protocol buffer representations back to TextPart, FilePart, and DataPart.
• spec-grpc/src/test/java/io/a2a/grpc/mapper/StreamResponseMapperTest.java
  • Updated TextPart instantiations to include null for the new metadata parameter in test cases.
• spec-grpc/src/test/java/io/a2a/grpc/utils/ToProtoTest.java
  • Updated TextPart instantiations to include null for the new metadata parameter in test cases.
• spec/src/main/java/io/a2a/spec/DataPart.java
  • Imported java.util.HashMap and java.util.Map.
  • Added @Nullable Map<String, Object> metadata to the DataPart record constructor.
  • Updated the build method in DataPart.Builder to include the metadata parameter.
  • Added a metadata field and a metadata setter method to DataPart.Builder.
• spec/src/main/java/io/a2a/spec/FilePart.java
  • Imported java.util.Map and org.jspecify.annotations.Nullable.
  • Added @Nullable Map<String, Object> metadata to the FilePart record constructor.
• spec/src/main/java/io/a2a/spec/Message.java
  • Reformatted constructor parameters for improved readability without functional changes.
• spec/src/main/java/io/a2a/spec/TextPart.java
  • Imported java.util.Map and org.jspecify.annotations.Nullable.
  • Added @Nullable Map<String, Object> metadata to the TextPart record constructor.

Activity

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[gemini-code-assist]

Code Review

This pull request successfully adds support for an optional metadata field to TextPart, FilePart, and DataPart, which is a great enhancement for providing more context. The changes correctly update the domain objects, JSON serializers/deserializers, and gRPC mappers.

My review includes a few suggestions to improve the implementation:

• A critical fix for invalid characters in pom.xml.
• A fix for a potential NullPointerException in the DataPart builder.
• Suggestions for refactoring to reduce code duplication.
• A recommendation to add tests for the new metadata functionality to ensure correctness.

I also noticed that a dependency for testcontainers was added in pom.xml. This seems unrelated to the main goal of this PR. It's generally a good practice to keep pull requests focused on a single feature or fix to make them easier to review and merge.

[kabir]

Needs a rebase