fix(powersync): Don't flush records when diff trigger isn't setup yet when using on-demand mode.

[Chriztiaan]

🎯 Changes

Users reported an error that occurs during startup when using on-demand: An error has been detected in the sync handler Error: no such table: __XXXX_tracking_6bed0e00. During initialisation we were flushing records before the diff trigger was setup.

This change simply skips flushing if the diff trigger hasn't been setup yet.

✅ Checklist

• I have tested this code locally with pnpm test.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.

Summary by CodeRabbit

• Bug Fixes
  • Fixed a non-critical error being logged during startup in on-demand sync mode.
  • Improved initialization to prevent unnecessary operations when sync tracking is not yet configured.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 068a86bc-4943-433b-82f5-708d493861ca

📥 Commits

Reviewing files that changed from the base of the PR and between 4d1abde and e830ffe.

📒 Files selected for processing (2)

• .changeset/five-turtles-yell.md
• packages/powersync-db-collection/src/powersync.ts

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📝 Walkthrough

Walkthrough

This PR adds defensive null checks to prevent flushing and disposing a diff trigger that hasn't been created yet during on-demand sync initialization, eliminating non-critical errors logged at startup in the loadSubset path.

Changes

Diff trigger initialization safety

Layer / File(s)	Summary
Guard diff trigger initialization in load/unload paths .changeset/five-turtles-yell.md, packages/powersync-db-collection/src/powersync.ts	Changeset documents that startup now skips flushing when diffTrigger is unconfigured. Code guards check disposeTracking before flushing/disposing in both the unload path (when last predicate is removed) and load path (on first subscription).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Suggested reviewers

• samwillis

Poem

🐰 A trigger that's not yet begun,
Now knows not to flush in the sun,
Guards catch the case,
At startup's own pace,
Errors begone—initialization is won! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main fix: preventing record flushing during initialization when the diff trigger isn't configured in on-demand mode.
Description check	✅ Passed	The description follows the template structure with clear sections explaining the issue, solution, and confirms testing and changeset generation.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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