fix: allow setitem over nonopen arg

hansel/crumb.py

@@ -162,7 +162,11 @@ def _open_arg_items(self):
 
     def _last_open_arg(self):
         """ Return the name and idx of the last (right-most) open argument."""
-        for dpth, arg in reversed(list(self._open_arg_items())):
+        open_args = list(self._open_arg_items())
+        if not open_args:
+            return None, None
+
+        for dpth, arg in reversed(open_args):
             return dpth, arg
 
     def _first_open_arg(self):
@@ -408,7 +412,7 @@ def _check_args(self, arg_names, self_args):
         if not anames and not aself:
             return
 
-        if not aself:
+        if not aself or aself is None:
             raise AttributeError('This Crumb has no remaining arguments: {}.'.format(self.path))
 
         if not anames.issubset(aself):
@@ -522,6 +526,9 @@ def values_map(self, arg_name='', check_exists=False):
         if not arg_name:
             _, arg_name = self._last_open_arg()
 
+        if arg_name is None:
+            return [list(self.arg_values.items())]
+
         arg_deps   = self._arg_parents(arg_name)
         values_map = None
         for arg in arg_deps:
@@ -594,8 +601,10 @@ def ls(self, arg_name='', fullpath=True, make_crumbs=True, check_exists=True):
         if not arg_name:
             _, arg_name = self._last_open_arg()
 
-        self._check_open_args([arg_name])
-        self._check_for_ls(make_crumbs, fullpath)
+        if arg_name is not None:
+            self._check_args([arg_name], self.all_args())
+
+        self._check_ls_params(make_crumbs, fullpath)
         values_map = self.values_map(arg_name, check_exists=check_exists)
         if fullpath:
             paths = self.build_paths(values_map, make_crumbs=make_crumbs)
@@ -604,7 +613,7 @@ def ls(self, arg_name='', fullpath=True, make_crumbs=True, check_exists=True):
 
         return sorted(paths)
 
-    def _check_for_ls(self, make_crumbs, fullpath):
+    def _check_ls_params(self, make_crumbs, fullpath):
         """ Raise errors if the arguments are not good for ls function."""
         # if the first chunk of the path is a parameter, I am not interested in this (for now)
         # check if the path is absolute, if not raise an NotImplementedError
@@ -709,9 +718,6 @@ def __getitem__(self, arg_name):
             return self.ls(arg_name, fullpath=False, make_crumbs=False, check_exists=True)
 
     def __setitem__(self, key, value):
-        if not _has_arg(self.path, arg_name=key):
-            raise KeyError("Expected `arg_name` to be one of ({}),"
-                           " got {}.".format(list(self.open_args()), key))
         _ = self.update(**{key: value})
 
     def __ge__(self, other):

hansel/tests/test_crumb.py

@@ -510,6 +510,33 @@ def test_exists2(tmp_crumb):
     assert not tmp_crumb.exists()
 
 
+def test_setitem(tmp_crumb):
+    assert not op.exists(tmp_crumb.split()[0])
+
+    values_dict = {'session_id': ['session_{:02}'.format(i) for i in range(2)],
+                   'subject_id': ['subj_{:03}'.format(i)    for i in range(3)],
+                   'modality':   ['anat'],
+                   'image':      ['mprage1.nii', 'mprage2.nii', 'mprage3.nii'],
+                  }
+
+    assert not tmp_crumb.exists()
+
+    _ = mktree(tmp_crumb, list(ParameterGrid(values_dict)))
+
+    cr = list(tmp_crumb.ls())[0]
+
+    assert not list(cr.open_args())
+
+    assert cr['image'] == [values_dict['image'][0]]
+
+    cr['image'] = 'mprage2.nii'
+
+    assert cr['image'] == ['mprage2.nii']
+
+    assert 'mprage2.nii' in cr.path
+    assert 'mprage2.nii' in cr.ls()[0].path
+
+
 def test_contains(tmp_crumb):
     assert 'modality'   in tmp_crumb
     assert 'subject_id' in tmp_crumb