fix: Add missing extensions to Artifact and Message #409

fjuma · 2025-10-29T14:44:19Z

Description

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Ensure the tests pass
Appropriate READMEs were updated (if necessary)

Fixes #408 🦕

gemini-code-assist · 2025-10-29T14:44:40Z

Summary of Changes

Hello @fjuma, 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 introduces a significant enhancement to the core Artifact and Message data structures by adding a new extensions field. This change allows for the inclusion of arbitrary string-based extensions, improving the extensibility and adaptability of these fundamental objects. The modifications span across the model definitions, their builders, and the utility layers responsible for their creation and serialization, ensuring seamless integration and proper handling of this new capability.

Highlights

Model Enhancement: The Artifact and Message data models have been extended to include a new extensions field, which is a list of strings, allowing for greater flexibility and custom data association.
Constructor and Builder Updates: Constructors and Builder patterns for both Artifact and Message classes have been updated to properly incorporate and manage the new extensions field.
gRPC Integration: The ProtoUtils class has been modified to correctly map the extensions list when converting between gRPC MessageOrBuilder/ArtifactOrBuilder and the internal Message/Artifact objects.
Utility and Test Adjustments: Related utility methods in ArtifactUtils and serialization tests in EventSerializationTest have been updated to align with the new Artifact constructor signature, ensuring compatibility and correct behavior.

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Code Review

This pull request adds a missing extensions field to the Artifact and Message data models, propagating the change through constructors, builders, and serialization/deserialization logic in related test and utility classes. The changes are correct and follow the existing patterns. I've added a couple of suggestions to improve the immutability of the Artifact and Message classes by making defensive copies of the new extensions list, which is a good practice for data model objects, especially when using records or aiming for immutability.

gemini-code-assist · 2025-10-29T14:46:18Z

spec/src/main/java/io/a2a/spec/Artifact.java

+        public Builder extensions(List<String> extensions) {
+            this.extensions = extensions;
+            return this;
+        }


To ensure the immutability of the Artifact record, it's a good practice to create a defensive copy of the extensions list. Assigning the list directly allows the Artifact's internal state to be modified from outside if a mutable list is passed to the builder. This would violate the immutability contract of a record.

I noticed that the parts(Part<?>... parts) method correctly uses List.of() to create an immutable list. This new extensions method should follow a similar robust pattern.

For consistency and robustness, you might also consider applying this to other collection-based builder methods like parts(List<Part<?>> parts) and metadata(Map<String, Object> metadata).

Suggested change

public Builder extensions(List<String> extensions) {

this.extensions = extensions;

return this;

}

public Builder extensions(List<String> extensions) {

this.extensions = (extensions == null) ? null : List.copyOf(extensions);

return this;

}

gemini-code-assist · 2025-10-29T14:46:19Z

spec/src/main/java/io/a2a/spec/Message.java

        this.taskId = taskId;
        this.referenceTaskIds = referenceTaskIds;
        this.metadata = metadata;
+        this.extensions = extensions;


The Message class appears to be designed as mostly immutable (with final fields), but assigning the extensions list directly can break this if a mutable list is provided. This would allow the internal state of the Message object to be changed after its construction. To ensure immutability for this field, you should create a defensive copy of the list.

For completeness, you might consider applying the same pattern to other collection fields like parts, referenceTaskIds, and metadata to make the class more robustly immutable (acknowledging that contextId and taskId are mutable by design).

Suggested change

this.extensions = extensions;

this.extensions = (extensions == null) ? null : List.copyOf(extensions);

Backporting #409 to 0.3.x Depends on #412

# Description Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly: - [x] Follow the [`CONTRIBUTING` Guide](../CONTRIBUTING.md). - [x] Make your Pull Request title in the <https://www.conventionalcommits.org/> specification. - Important Prefixes for [release-please](https://github.com/googleapis/release-please): - `fix:` which represents bug fixes, and correlates to a [SemVer](https://semver.org/) patch. - `feat:` represents a new feature, and correlates to a SemVer minor. - `feat!:`, or `fix!:`, `refactor!:`, etc., which represent a breaking change (indicated by the `!`) and will result in a SemVer major. - [x] Ensure the tests pass - [x] Appropriate READMEs were updated (if necessary) Fixes a2aproject#408 🦕

gemini-code-assist bot reviewed Oct 29, 2025

View reviewed changes

fix: Add missing extensions to Artifact and Message

5b3efc5

fjuma force-pushed the spec branch from 94dd3b2 to 5b3efc5 Compare October 29, 2025 14:51

kabir approved these changes Oct 29, 2025

View reviewed changes

kabir merged commit f9cfbdd into a2aproject:main Oct 29, 2025
10 checks passed

fjuma mentioned this pull request Oct 29, 2025

fix: Add missing extensions to Artifact and Message #411

Merged

kabir pushed a commit that referenced this pull request Nov 3, 2025

fix: Add missing extensions to Artifact and Message (#411)

fd474fa

Backporting #409 to 0.3.x Depends on #412

jmesnil added this to the 1.0.0 milestone Dec 11, 2025

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	this.extensions = extensions;
	this.extensions = (extensions == null) ? null : List.copyOf(extensions);

fix: Add missing extensions to Artifact and Message #409

fix: Add missing extensions to Artifact and Message #409

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fjuma commented Oct 29, 2025

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