GitHub issue #7061: Custom Dataset | Still Raise Error while handling errors in _generate_examples
State: open | Created: 2024-07-22T21:18:12Z

### Describe the bug

I follow this [example](https://discuss.huggingface.co/t/error-handling-in-iterabledataset/72827/3) to handle errors in custom dataset. I am writing a dataset script which read jsonl files and i need to handle errors and continue reading files without raising exception and exit the execution.

```
def _generate_examples(self, filepaths):
        errors=[]
        
        id_ = 0
        for filepath in filepaths:
            try:
                with open(filepath, 'r') as f:
                    for line in f:
                        json_obj = json.loads(line)
                        
                        yield id_, json_obj
                        id_ += 1
            except Exception as exc:     
                logger.error(f"error occur at filepath: {filepath}")      
                errors.append(error)
```

seems the logger.error is printed but still exception is raised the the run is exit.

```
Downloading and preparing dataset custom_dataset/default to /home/myuser/.cache/huggingface/datasets/custom_dataset/default-a14cdd566afee0a6/1.0.0/acfcc9fb9c57034b580c4252841
ERROR: datasets_modules.datasets.custom_dataset.acfcc9fb9c57034b580c4252841bb890a5617cbd28678dd4be5e52b81188ad02.custom_dataset: 2024-07-22 10:47:42,167: error occur at filepath: '/home/myuser/ds/corrupted-file.jsonl
Traceback (most recent call last):
  File "/home/myuser/.cache/huggingface/modules/datasets_modules/datasets/custom_dataset/ac..2/custom_dataset.py", line 48, in _generate_examples
    json_obj = json.loads(line)
  File "myenv/lib/python3.8/json/__init__.py", line 357, in loads
    return _default_decoder.decode(s)
  File "myenv/lib/python3.8/json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "myenv/lib/python3.8/json/decoder.py", line 353, in raw_decode
    obj, end = self.scan_once(s, idx)
json.decoder.JSONDecodeError: Invalid control character at: line 1 column 4 (char 3)
Generating train split: 0 examples [00:06, ? examples/s]>
RemoteTraceback: 
"""
Traceback (most recent call last):
  File "myenv/lib/python3.8/site-packages/datasets/builder.py", line 1637, in _prepare_split_single
    num_examples, num_bytes = writer.finalize()
  File "myenv/lib/python3.8/site-packages/datasets/arrow_writer.py", line 594, in finalize
    raise SchemaInferenceError("Please pass `features` or at least one example when writing data")
datasets.arrow_writer.SchemaInferenceError: Please pass `features` or at least one example when writing data

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "myenv/lib/python3.8/site-packages/multiprocess/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "myenv/lib/python3.8/site-packages/datasets/utils/py_utils.py", line 1353, in 
_write_generator_to_queue
    for i, result in enumerate(func(**kwargs)):
  File "myenv/lib/python3.8/site-packages/datasets/builder.py", line 1646, in _prepare_split_single
    raise DatasetGenerationError("An error occurred while generating the dataset") from e
datasets.builder.DatasetGenerationError: An error occurred while generating the dataset
"""

The above exception was the direct cause of the following exception:


│                                                                                                  │
│ myenv/lib/python3.8/site-packages/datasets/utils/py_utils. │
│ py:1377 in <listcomp>                                                                            │
│                                                                                                  │
│   1374 │   │   │   │   if all(async_result.ready() for async_result in async_results) and queue  │
│   1375 │   │   │   │   │   break                                                                 │
│   1376 │   │   # we get the result in case there's an error to raise                             │
│ ❱ 1377 │   │   [async_result.get() for async_result in async_results]                            │
│   1378                                                                                           │
│                                                                                                  │
│ ╭──────────────────────────────── locals ─────────────────────────────────╮                      │
│ │           .0 = <list_iterator object at 0x7f2cc1f0ce20>                 │                      │
│ │ async_result = <multiprocess.pool.ApplyResult object at 0x7f2cc1f79c10> │                      │
│ ╰─────────────────────────────────────────────────────────────────────────╯                      │
│                                                                                                  │
│ myenv/lib/python3.8/site-packages/multiprocess/pool.py:771 │
│ in get                                                                                           │
│                                                                                                  │
│   768 │   │   if self._success:                                                                  │
│   769 │   │   │   return self._value                                                             │
│   770 │   │   else:                                                                              │
│ ❱ 771 │   │   │   raise self._value                                                              │
│   772 │                                                                                          │
│   773 │   def _set(self, i, obj):                                                                │
│   774 │   │   self._success, self._value = obj                                                   │
│                                                                                                  │
│ ╭────────────────────────────── locals ──────────────────────────────╮                           │
│ │    self = <multiprocess.pool.ApplyResult object at 0x7f2cc1f79c10> │                           │
│ │ timeout = None                                                     │                           │
│ ╰────────────────────────────────────────────────────────────────────╯                           │

DatasetGenerationError: An error occurred while generating the dataset
```

### Steps to reproduce the bug

same as above

### Expected behavior

should handle error and continue reading remaining files

### Environment info

python 3.9