# Multi-level error retrieval and state-decision audit

This report is based on static inspection of the bundled `source_reference/dobot_core/dobot_tcp.py` and `dobot_error.py`. It is not a hardware or network test.

## Call paths

| Public API (via `DobotCtrl`) | `DobotTcp` | `DobotErrorManager` | Result |
|---|---|---|---|
| `get_error()` | `get_error()` | `get_error()` → `_get_error_records()` | Alarm ID list from `GetErrorID()` |
| `get_error_code()` | `get_error_code()` | `get_error_code()` → `_get_error_records()` | First ID, or `0` if empty |
| `get_error_count()` | `get_error_count()` | `get_error_count()` → `_get_error_records()` | Record count |
| `check_error()` | `check_error()` | `get_error_count()` → `_get_error_records()` | `True` when count is zero |
| `get_error_info(index)` | Same name | Same name → `_get_error_records()` → `_error_record_info()` | `None` for out-of-range index |
| `get_current_error_info()` | Same name | Same name → `_get_error_records()` → `_error_record_info()` | Enriched alarm records |
| `error_description` | Same property | Same property → `get_current_error_info()` | Empty string when no records |

## Where failures can become normal-looking values

1. `_get_error_records()` returns `[]` if the Dashboard object is `None`.
2. A nonzero or unparsable leading `GetErrorID()` return code is logged and converted to `[]`.
3. `_parse_error_groups()` returns `[]` for empty or malformed replies, invalid JSON, or non-list payloads.
4. Consequently, `get_error() == []`, `get_error_count() == 0`, `get_error_code() == 0`, and `check_error() is True` **do not uniquely establish that no alarm exists**.
5. If `dashboard.GetErrorID()` raises an exception, `_get_error_records()` has no handler around that call, so the exception may propagate. **Not every communication failure becomes an empty list.**

## Feedback-dependent motion error detection

`motion_error_active()` catches `RuntimeError` from `_state_getter("ErrorStatus", timeout=0.1)` and substitutes `error_status=False`. With `query_error_id=False`, it does not query `GetErrorID()` unless Feedback indicates an error. With `query_error_id=True` or `ErrorStatus=True`, it queries `_get_error_records()`.

`wait_motion_start_or_error()` monitors for 0.25 seconds by default, then performs a final check with `query_error_id=True`. This is a **limited post-acceptance check**, not verification of the entire motion.

## Operational implications

- Do not infer communication health solely from `check_error()`.
- Some error-retrieval failures cannot be distinguished from no-alarm responses through the current public return values.
- External Dashboard exceptions depend on its implementation and are not guaranteed by this report.
- This documents observed source behavior; it does not modify the implementation.