[copilot-finds] Bug: Export job orchestrator reports zero progress statistics on batch failure

[github-actions]

Problem

In packages/durabletask-js-export-history/src/orchestrators/export-job-orchestrator.ts (lines 160–165), when a batch of export activities fails after exhausting all retry attempts, the orchestrator commits a checkpoint with hardcoded zero values:

yield* commitCheckpoint(ctx, jobEntityId, {
  scannedInstances: 0,       // ← should be scannedCount
  exportedInstances: 0,      // ← should be batchResult.exportedCount
  failures: batchResult.failures,
} as CommitCheckpointRequest);

The actual values are available: scannedCount (line 121) tracks how many instances were listed, and batchResult.exportedCount (returned from processBatchWithRetry at line 220) tracks how many were successfully exported before the batch was marked as failed.

Root Cause

The failure-path checkpoint was written with literal 0 values instead of the computed variables used in the success path (lines 145–148). This appears to be a copy-paste oversight — the success path correctly uses scannedCount and batchResult.exportedCount.

Impact

The ExportJob entity accumulates scannedInstances and exportedInstances via addition in commitCheckpoint() (entity line 142–143). Reporting 0 means:

• Progress statistics undercount real work. If 100 instances are scanned and 80 are exported before 20 fail, the job's counters show 0/0 for that batch instead of 100/80.
• Operators see inaccurate progress data when monitoring long-running export jobs, making it harder to assess how much work was completed before failure.
• The failure-path and success-path behaviors are asymmetric, which is confusing for anyone reading the code.

This affects the @microsoft/durabletask-js-export-history package.

Proposed Fix

Replace the hardcoded zeros with the actual computed values, matching the success-path behavior:

yield* commitCheckpoint(ctx, jobEntityId, {
  scannedInstances: scannedCount,
  exportedInstances: batchResult.exportedCount,
  failures: batchResult.failures,
} as CommitCheckpointRequest);

[github-actions]

Fix Ready

The fix is ready on branch copilot-finds/bug/fix-batch-failure-progress-stats.

PR could not be created automatically because the repository has GitHub Actions PR creation disabled. A maintainer can create a PR from this branch.

Changes:

• packages/durabletask-js-export-history/src/orchestrators/export-job-orchestrator.ts — Replace hardcoded 0 values with scannedCount and batchResult.exportedCount in the failure-path checkpoint (2-line change)
• packages/durabletask-js-export-history/test/export-job-orchestrator.spec.ts — 3 new unit tests covering the failure, all-fail, and success scenarios

Verification:

• All 1010 existing tests pass ✅
• 3 new tests pass ✅
• Lint passes ✅
• New tests fail against the original code and pass with the fix ✅