fix(sse): skip empty keepalive events

[agufagit]

Summary

• skip empty SSE keepalive/comment events before forwarding to the GraphQL response parser
• keep empty unnamed SSE events as unknown instead of treating them as completion
• add coverage for comment keepalives, named empty events, and terminal complete events

Tests

• go test ./pkg/engine/datasource/graphql_datasource/subscriptionclient/transport

[claude]

Claude Code Review

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 1c9643fe-435b-4dbf-aa1a-26ee2b260295

📥 Commits

Reviewing files that changed from the base of the PR and between b08f86e and 01fd2c0.

📒 Files selected for processing (2)

• v2/pkg/engine/datasource/graphql_datasource/subscriptionclient/transport/sse_conn.go
• v2/pkg/engine/datasource/graphql_datasource/subscriptionclient/transport/sse_conn_test.go

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📝 Walkthrough

Walkthrough

This PR refines SSE connection handling in the GraphQL subscription client to filter empty keepalive events from reaching the downstream message parser, while preserving terminal complete events. The implementation also corrects the default message type for unknown events from Complete to Unknown. A test validates the filtering behavior.

Changes

SSE Keepalive Event Filtering

Layer / File(s)	Summary
Event filtering and message type handling v2/pkg/engine/datasource/graphql_datasource/subscriptionclient/transport/sse_conn.go	The readLoop condition now skips empty events except terminal complete events, preventing keepalive comments from propagating downstream. The parseEvent default case returns MessageTypeUnknown instead of MessageTypeComplete for unknown event types with no data.
Keepalive filtering validation v2/pkg/engine/datasource/graphql_datasource/subscriptionclient/transport/sse_conn_test.go	New test subcase confirms that keepalive comment lines and empty SSE events are filtered out while valid next and complete events are delivered to the handler.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix(sse): skip empty keepalive events' accurately and concisely describes the main change: filtering out empty SSE keepalive events before they reach the downstream GraphQL parser.
Description check	✅ Passed	The description provides clear, related context about the changes: skipping empty SSE keepalive events, handling empty unnamed events as unknown rather than complete, and adding test coverage.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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• Create PR with unit tests

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