[MRG] Turn off datatype check (#744)

* Fixing datatype check.

* Fix pr number.

* Update changelog

* Fix unit test.

* Fixing docstring.

* Rework Notes section

* Example indentation

Co-authored-by: Richard Höchenberger <richard.hoechenberger@gmail.com>

doc/whats_new.rst

@@ -43,10 +43,11 @@ Enhancements
 - Improve the ``Convert iEEG data to BIDS`` tutorial to include a note on how BIDS and MNE-Python coordinate frames are handled, by `Adam Li`_ (:gh:`717`)
 - More detailed error messages when trying to write modified data via :func:`mne_bids.write_raw_bids`, by `Richard Höchenberger`_ (:gh:`719`)
 - If ``check=True``, :class:`mne_bids.BIDSPath` now checks the ``space`` entity to be valid according to BIDS specification Appendix VIII, by `Stefan Appelhoff`_ (:gh:`724`)
-- ``BIDSPath.root`` now automatically expands ``~`` to the user's home directory, by `Richard Höchenberger`_ (:gh:`725`)
+- Data types that are currently unsupported by MNE-BIDS (e.g. ``dwi``, ``func``) can now be used in :class:`mne_bids.BIDSPath` by setting ``check=False``, by `Adam Li`_ (:gh:`744`)
 - Arbitrary file names can now be represented as a `BIDSPath`` by passing the entire name as ``suffix`` and setting ``check=False``, by `Adam Li`_ (:gh:`729`)
 - Add support for MNE's flux excitation channel (``exci``), by `Maximilien Chaumon`_ (:gh:`728`)
 - :meth:`mne_bids.BIDSPath.match` gained a new parameter ``check``; when setting ``check=True``, ``match()`` will only return paths that conform to BIDS, by `Richard Höchenberger`_ (:gh:`726`)
+- ``BIDSPath.root`` now automatically expands ``~`` to the user's home directory, by `Richard Höchenberger`_ (:gh:`725`)
 
 API and behavior changes
 ^^^^^^^^^^^^^^^^^^^^^^^^

mne_bids/path.py

@@ -228,15 +228,15 @@ class BIDSPath(object):
     Examples
     --------
     >>> bids_path = BIDSPath(subject='test', session='two', task='mytask',
-                                 suffix='ieeg', extension='.edf')
+                             suffix='ieeg', extension='.edf')
     >>> print(bids_path.basename)
     sub-test_ses-two_task-mytask_ieeg.edf
     >>> bids_path
     BIDSPath(root: None,
     basename: sub-test_ses-two_task-mytask_ieeg.edf)
     >>> # copy and update multiple entities at once
     >>> new_bids_path = bids_path.copy().update(subject='test2',
-                                                   session='one')
+                                                session='one')
     >>> print(new_bids_path.basename)
     sub-test2_ses-one_task-mytask_ieeg.edf
     >>> # printing the BIDSPath will show relative path when
@@ -261,15 +261,20 @@ class BIDSPath(object):
 
     Notes
     -----
-    BIDS entities are separated generally with a ``"_"`` character, while
-    entity key/value pairs are separated with a ``"-"`` character (e.g.
-    ``subject``, ``session``, ``task``, etc.). There are checks performed
-    to make sure that there are no ``'-'``, ``'_'``, or ``'/'`` characters
-    associated with any of these entities.
+    BIDS entities are generally separated with a ``"_"`` character, while
+    entity key/value pairs are separated with a ``"-"`` character.
+    There are checks performed to make sure that there are no ``'-'``, ``'_'``,
+    or ``'/'`` characters contained in any entity keys or values.
 
     To represent a filename such as ``dataset_description.json``,
     one can set ``check=False``, and pass ``suffix='dataset_description'``
     and ``extension='.json'``.
+
+    ``BIDSPath`` can also be used to represent file and folder names of data
+    types that are not yet supported through MNE-BIDS, but are recognized by
+    BIDS. For example, one can set ``datatype`` to ``dwi`` or ``func`` and
+    pass ``check=False`` to represent diffusion-weighted imaging and
+    functional MRI paths.
     """
 
     def __init__(self, subject=None, session=None,
@@ -552,7 +557,8 @@ def update(self, *, check=None, **kwargs):
                 continue
 
             if key == 'datatype':
-                if val is not None and val not in ALLOWED_DATATYPES:
+                if val is not None and val not in ALLOWED_DATATYPES \
+                        and self.check:
                     raise ValueError(f'datatype ({val}) is not valid. '
                                      f'Should be one of '
                                      f'{ALLOWED_DATATYPES}')

mne_bids/tests/test_path.py

@@ -504,9 +504,13 @@ def test_bids_path(return_bids_test_dir):
                          suffix=suffix, check=False)
 
     # also inherits error check from instantiation
-    # always error check datatype
+    # always error check entities though
+    with pytest.raises(ValueError, match='Key must be one of'):
+        bids_path.copy().update(blah='blah-entity')
+
+    # error check datatype if check is turned back on
     with pytest.raises(ValueError, match='datatype .* is not valid'):
-        bids_path.copy().update(datatype=error_kind)
+        bids_path.copy().update(check=True, datatype=error_kind)
 
     # does not error check on space if check=False ...
     BIDSPath(subject=subject_id, space='foo', suffix='eeg', check=False)