nbformat.reader.NotJSONError

[alexlenail]

Tried to merge a couple jupyterlab notebooks, but got an error:

nbmerge a.ipynb b.ipynb > a.ipynb
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/nbformat/reader.py", line 14, in parse_json
    nb_dict = json.loads(s, **kwargs)
  File "/usr/local/Cellar/python@3.7/3.7.10_3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/__init__.py", line 348, in loads
    return _default_decoder.decode(s)
  File "/usr/local/Cellar/python@3.7/3.7.10_3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/local/Cellar/python@3.7/3.7.10_3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/local/bin/nbmerge", line 8, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.7/site-packages/nbmerge/__init__.py", line 194, in main
    plan['boundary_key'])
  File "/usr/local/lib/python3.7/site-packages/nbmerge/__init__.py", line 72, in merge_notebooks
    nb = read_notebook(fp, as_version=4)
  File "/usr/local/lib/python3.7/site-packages/nbformat/__init__.py", line 143, in read
    return reads(buf, as_version, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/nbformat/__init__.py", line 73, in reads
    nb = reader.reads(s, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/nbformat/reader.py", line 58, in reads
    nb_dict = parse_json(s, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/nbformat/reader.py", line 17, in parse_json
    raise NotJSONError(("Notebook does not appear to be JSON: %r" % s)[:77] + "...") from e
nbformat.reader.NotJSONError: Notebook does not appear to be JSON: ''...

I can't vouch for these notebooks being valid JSON, but they are valid jupyter notebooks.

[alexlenail]

In a lovely turn of events, I tried the exact same thing again, changing nothing, and it worked.