Sync mode selection should validate against stream's supported_sync_modes

[devin-ai-integration]

Summary

When building the configured catalog, the _get_sync_mode helper function unconditionally falls back to SyncMode.incremental, even for streams that only support full_refresh. This can cause connector failures for streams that don't support incremental sync.

Background

This issue was identified during code review of PR #899 (force_full_refresh fix). The current behavior predates that PR, so it's not a regression - but it's a valid edge case that should be addressed.

Requested by: Aaron ("AJ") Steers (@aaronsteers) (AJ Steers)

Current Behavior

def _get_sync_mode(stream: AirbyteStream) -> SyncMode:
    supported_modes = getattr(stream, "supported_sync_modes", None)

    if force_full_refresh:
        if supported_modes and SyncMode.full_refresh in supported_modes:
            return SyncMode.full_refresh
        return SyncMode.incremental  # BUG: stream might not support incremental

    return SyncMode.incremental  # BUG: stream might only support full_refresh

Expected Behavior

The selected sync mode should always be validated against supported_sync_modes when that attribute is present:

def _get_sync_mode(stream: AirbyteStream) -> SyncMode:
    supported_modes = getattr(stream, "supported_sync_modes", None)

    if force_full_refresh:
        if supported_modes and SyncMode.full_refresh in supported_modes:
            return SyncMode.full_refresh
        if supported_modes and SyncMode.incremental in supported_modes:
            return SyncMode.incremental
        return SyncMode.full_refresh  # fallback for unknown/empty

    # Default: prefer incremental if supported, otherwise full_refresh
    if supported_modes and SyncMode.incremental in supported_modes:
        return SyncMode.incremental
    if supported_modes and SyncMode.full_refresh in supported_modes:
        return SyncMode.full_refresh
    return SyncMode.incremental  # preserve backwards compat for unknown

Affected Code

• airbyte/sources/base.py - _get_sync_mode helper function (around line 449)

References

• CodeRabbit comment: fix: Pass explicit SyncMode.full_refresh when force_full_refresh=True #899 (comment)
• Related PR: fix: Pass explicit SyncMode.full_refresh when force_full_refresh=True #899