[nevridge]

Closes #197

Summary

Pure refactor of TaskRepository.UpdateAsync: the four near-identical "if changed, emit history event" blocks (Title, Priority, Description, DueDate) are replaced by one private helper, AddFieldChangedEvent(int taskId, bool changed, string eventType, Func<string> summary), placed after FormatDueDate. Task history is unchanged for users.

• Each call site keeps its own explicit comparison: Ordinal string.Equals for Title and Description, != for Priority and DueDate.
• EventType and ChangeSummary strings are byte-identical to main, because the frontend TaskHistoryPanel maps them.
• Event order is unchanged (Title, Priority, Description, DueDate, then the status block).
• Each event keeps its own DateTime.UtcNow.
• The combined Completed/Reopened/StatusChanged/Blocked block and the originals resolution are untouched.
• The Detached branch is kept, with a comment explaining it is a safety net for callers that pass untracked entities. It is not removable: an existing test exercises it.
• No API, database, migration, controller or frontend change.

Files changed

• TaskFlow.Api/Repositories/TaskRepository.cs: the helper, four call sites, and the Detached comment. The read paths at the top of the file are untouched, which limits conflicts with perf(api): add AsNoTracking to read-only repository query paths (#196) #359 ([Perf] Add AsNoTracking() to read-only repository query paths #196).
• TaskFlow.Api.Tests/Repositories/TaskRepositoryUpdateEventTests.cs (new): 20 characterization test cases (theory rows counted). They were written and run green against the unmodified code first, then re-run after the refactor.
• No existing test file is edited.

Tests

As reported by the test-verifier (CI will run them again):

• dotnet format TaskFlow.sln --verify-no-changes: exit 0
• dotnet build TaskFlow.sln -c Release: 0 warnings, 0 errors
• Full backend suite: 663 passed, 0 failed
• Coverage threshold of 75%: passed (exit 0)

New tests cover exact summaries for each field, Priority-only, single-event assertions, ordering (including field events before the status event), the case-only Title change, an Ordinal-only Description change, null/empty Description swaps, same-value no-ops, a DueDate with a different Kind (no event), InProgress falling through to StatusChanged, and Detached title and priority changes.

Validator status

Critical 0, Important 0, Minor 1 (after one rework pass).

Residual, for awareness:

• The Detached comment says the branch is covered by "the Detached-entity tests in TaskRepositoryTests"; only one such test is there, and the others are in the new file. Wording only.
• The Ordinal Description test catches a case-insensitive comparer but not a case-sensitive culture-sensitive one. Production code uses StringComparison.Ordinal.

Suggested follow-up issue (not filed)

Possible missed Description/DueDate event on the Detached path when the persisted value is null. The originals use persisted?.X ?? entry.OriginalValues..., and after Update(task) the fallback already equals the incoming value. This was found by code reading and is unverified, and no production caller reaches the Detached path. This PR neither hides nor alters it, and no test asserts it. It is worth verifying and fixing separately.

[nevridge]

Review: 💬 Comments

No issues found in this diff.

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_{Reviewed at 582918d · findings from pr-review + code-review, verified and triaged by @nevridge with Claude Code}