[2.0] Continue GLIDE scans across empty batches

[progys]

Closes #108.

Target

This fixes Spring Data Valkey 2.0.0. The defect was reproduced in the released v2.0.0 tag, and this branch is based on main, which currently points to the same commit as that tag.

Protocol and driver documentation

• The official Valkey SCAN documentation explicitly states that a call may return zero elements and that clients must continue while the returned cursor is non-zero. Its MATCH example also shows empty intermediate responses.
• The Valkey GLIDE migration guide's SCAN example processes keys only when a batch is non-empty but continues until cursor 0.

Change

An empty SCAN result does not mean iteration is complete when the returned cursor is non-zero. The GLIDE standalone cursor previously loaded only one batch per hasNext() call and returned false if that batch was empty, causing callers to stop before later matches were returned.

This change makes hasNext() keep loading batches until it finds a key or receives cursor zero. It also adds a deterministic unit test covering a non-empty batch, an empty intermediate batch with a non-zero cursor, and a final non-empty batch. The cursor Javadoc documents why empty intermediate batches must be skipped and links directly to the Valkey SCAN contract.

• I have read the Spring Data contribution guidelines.
• I used the project code format and did not include unrelated formatting changes.
• I submitted a test case that backs the change.
• I added myself as author in the headers of the classes I touched.

Tests

• ./mvnw test -pl spring-data-valkey -Dtest=ValkeyGlideKeyCommandsUnitTests — passes (1 test).
• make test — the new test passes, but the full suite fails in unrelated existing tests because the harness builds Valkey 8.1.1 while tests invoke commands not supported there, including HSETEX, HEXPIREAT, and XDELEX (28,706 run; 51 failures; 130 errors; 613 skipped).

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Review configuration:

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: 99d3e64c-48fc-4d25-8d70-7b70efacb67e

📥 Commits

Reviewing files that changed from the base of the PR and between 88c51a8 and 11ae5a1.

📒 Files selected for processing (1)

• spring-data-valkey/src/test/java/io/valkey/springframework/data/valkey/connection/valkeyglide/ValkeyGlideKeyCommandsUnitTests.java

📝 Walkthrough

Walkthrough

The GLIDE SCAN cursor now continues loading batches when an intermediate response is empty but has a non-zero cursor. A unit test verifies that keys after the empty batch are returned.

Changes

GLIDE SCAN continuation

Layer / File(s)	Summary
Cursor iteration behavior spring-data-valkey/src/main/java/io/valkey/springframework/data/valkey/connection/valkeyglide/ValkeyGlideKeyCommands.java	The cursor documentation describes empty intermediate batches. hasNext() now loads batches until it finds an item or reaches completion.
Regression coverage spring-data-valkey/src/test/java/io/valkey/springframework/data/valkey/connection/valkeyglide/ValkeyGlideKeyCommandsUnitTests.java	The test verifies that iteration returns keys before and after an empty batch and invokes SCAN for all three responses.

Suggested reviewers: jeremyprime

Priority: ➖ Normal

Change: Bug fix · Severity of issue fixed: Medium

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: continuing GLIDE scans across empty intermediate batches.
Description check	✅ Passed	The description directly explains the SCAN defect, the fix, the test coverage, and the test results.
Linked Issues check	✅ Passed	The GLIDE standalone scan cursor now loops in hasNext() while the current batch is empty and iteration is not finished. loadNextBatch() sets finished when the returned cursor is 0, so empty in…
Out of Scope Changes check	✅ Passed	The changes stay within issue #108. They update the affected GLIDE standalone scan cursor, add related SCAN contract Javadoc, and add focused unit coverage. No unrelated behavior or files are shown in…

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Actionable comments posted: 1

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Inline comments:
In
`@spring-data-valkey/src/test/java/io/valkey/springframework/data/valkey/connection/valkeyglide/ValkeyGlideKeyCommandsUnitTests.java`:
- Line 2: Update the copyright header in ValkeyGlideKeyCommandsUnitTests to use
“Copyright 2025-present the original author or authors.”

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: 08d34705-d636-4468-862f-e8a9cc30af68

📥 Commits

Reviewing files that changed from the base of the PR and between 427208e and 88c51a8.

📒 Files selected for processing (2)

• spring-data-valkey/src/main/java/io/valkey/springframework/data/valkey/connection/valkeyglide/ValkeyGlideKeyCommands.java
• spring-data-valkey/src/test/java/io/valkey/springframework/data/valkey/connection/valkeyglide/ValkeyGlideKeyCommandsUnitTests.java

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[progys]

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