fix constraint violation on sync

[hahn-kev]

related to sillsdev/languageforge-lexbox#1615

WordTags are linking objects between a word and a tag. There is a constraint that there can only be one row with the same tag and word id. If a sync comes in that creates a word tag which already exists, but the commit precedes the local word tag we run into this constraint violation.

Summary by CodeRabbit

• Bug Fixes

  • Improved duplicate prevention to ensure that duplicate tag relationships are not created, even if a duplicate entry is inserted with an earlier version.

• Tests

  • Added a new test to verify that the system prevents duplicate tag relationships when a duplicate is created before the current version.

• Refactor

  • Updated internal class structures and constructors for better maintainability and serialization support.
  • Enhanced snapshot processing logic to handle deleted entities more robustly.

[coderabbitai]

Walkthrough

This update refactors the TagWordChange class to use explicit constructors, including one marked with [JsonConstructor] for deserialization, and moves property initialization into these constructors. A new unit test is introduced to verify correct handling of duplicate tag-word relationships, especially when duplicates are inserted retroactively. Additionally, the snapshot processing logic in the repository is revised to group and process snapshots by deletion status, ensuring deleted entities are handled first and saving changes after each group. The early-exit condition in the ProjectSnapshot method for deleted root snapshots is removed.

Changes

File(s)	Change Summary
src/SIL.Harmony.Sample/Changes/TagWordChange.cs	Refactored TagWordChange to use explicit constructors, added [JsonConstructor] overload, moved property initialization into constructors, and added necessary namespace import.
src/SIL.Harmony.Tests/SnapshotTests.cs	Added a new test method to verify duplicate prevention when a duplicate is created before the current version.
src/SIL.Harmony/Db/CrdtRepository.cs	Modified snapshot processing to group by deletion status and process deleted entities first; moved save and error handling inside the group loop; removed early return for deleted root snapshots in ProjectSnapshot.

Sequence Diagram(s)

sequenceDiagram
    participant Test as SnapshotTests
    participant Repo as CrdtRepository
    participant Db as DbContext

    Test->>Repo: AddSnapshots(snapshots)
    loop For each group by deletion status (deleted first)
        Repo->>Db: Add snapshots in group
        Repo->>Repo: ProjectSnapshot for new EntityIds
        Repo->>Db: SaveChangesAsync()
        alt Exception occurs
            Repo->>Repo: Handle exception
        end
    end

Loading

Possibly related PRs

• Include snapshots from current commit when finding referencing snapshots #29: Originally introduced the TagWordChange class and its methods; directly related as the current PR refactors and extends this class.

Poem

In the code garden where snapshots bloom,
Constructors now have extra room.
Duplicates chased from every nook,
With tests to ensure a tidy look.
Snapshots grouped, deletions first—
Harmony’s logic, well-rehearsed!
🐇✨

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📜 Recent review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3145188 and c45f3bb.

📒 Files selected for processing (3)

• src/SIL.Harmony.Sample/Changes/TagWordChange.cs (1 hunks)
• src/SIL.Harmony.Tests/SnapshotTests.cs (1 hunks)
• src/SIL.Harmony/Db/CrdtRepository.cs (1 hunks)

🧰 Additional context used

🧬 Code Graph Analysis (1)

src/SIL.Harmony.Sample/Changes/TagWordChange.cs (1)

src/SIL.Harmony/Changes/CreateChange.cs (1)

• CreateChange (3-9)

🔇 Additional comments (5)

src/SIL.Harmony.Tests/SnapshotTests.cs (1)

125-142: Good test coverage for duplicate prevention.

This test effectively validates that the system correctly handles duplicate tag-word relationships even when they're inserted retroactively with an earlier timestamp. It directly addresses the constraint violation issue mentioned in the PR objectives, ensuring that duplicates are properly prevented regardless of insertion order.

src/SIL.Harmony/Db/CrdtRepository.cs (2)

259-281: Well-structured ordering for snapshot processing.

The modified code now groups snapshots by deletion status and processes deleted entities first, which effectively prevents constraint violations during synchronization. Saving changes after each group is also a good approach to isolate potential errors.

One minor suggestion:

-foreach (var grouping in snapshots.GroupBy(s => s.EntityIsDeleted).OrderByDescending(g => g.Key))//execute deletes first
+foreach (var grouping in snapshots.GroupBy(s => s.EntityIsDeleted).OrderByDescending(g => g.Key)) // Process deletes first to prevent constraint violations during sync

---

287-287: Improved handling of root deleted snapshots.

Removing the early-exit condition for deleted root snapshots ensures proper processing of all snapshot types, supporting the enhanced duplicate prevention mechanism.

src/SIL.Harmony.Sample/Changes/TagWordChange.cs (2)

1-2: Added JsonSerializer support.

Adding the System.Text.Json.Serialization namespace enables proper JSON serialization/deserialization, which is essential for handling sync operations.

---

8-24: Improved class design with explicit constructors.

Refactoring from a primary constructor to explicit constructors with a dedicated [JsonConstructor] improves serialization support while maintaining the same functionality. The readonly properties ensure immutability after initialization, which is a good practice for change objects.

This change directly addresses the PR objective of fixing constraint violations during sync by ensuring proper deserialization of TagWordChange objects, particularly when handling retroactive duplicate entries.

✨ Finishing Touches

• 📝 Generate Docstrings

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[myieye]

LGTM 👍