FIX: Make lists and dicts hashable

Resolves: #683.

bids/layout/layout.py

@@ -14,7 +14,7 @@
 import sqlalchemy as sa
 from bids_validator import BIDSValidator
 
-from ..utils import listify, natural_sort
+from ..utils import listify, natural_sort, hashablefy
 from ..external import inflect
 from ..exceptions import (
     BIDSDerivativesValidationError,
@@ -677,7 +677,7 @@ def get(self, return_type='object', target=None, scope='all',
             results = [x for x in results if target in x.entities]
 
             if return_type == 'id':
-                results = list(set([x.entities[target] for x in results]))
+                results = list(set([hashablefy(x.entities[target]) for x in results]))
                 results = natural_sort(results)
 
             elif return_type == 'dir':

bids/layout/tests/test_layout.py

@@ -457,6 +457,27 @@ def test_get_tr(layout_7t_trt):
     assert tr == 4.0
 
 
+def test_get_nonhashable_metadata(layout_ds117):
+    """Test nonhashable metadata values (#683)."""
+    assert layout_ds117.get_IntendedFor(subject=['01'])[0] == (
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-01_bold.nii.gz",
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-02_bold.nii.gz",
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-03_bold.nii.gz",
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-04_bold.nii.gz",
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-05_bold.nii.gz",
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-06_bold.nii.gz",
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-07_bold.nii.gz",
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-08_bold.nii.gz",
+       "ses-mri/func/sub-01_ses-mri_task-facerecognition_run-09_bold.nii.gz",
+    )
+
+    landmarks = layout_ds117.get_AnatomicalLandmarkCoordinates(subject=['01'])[0]
+    assert landmarks["Nasion"] == (43, 111, 95)
+    assert landmarks["LPA"] == (140, 74, 16)
+    assert landmarks["RPA"] == (143, 74, 173)
+
+
+
 def test_to_df(layout_ds117):
     # Only filename entities
     df = layout_ds117.to_df()

bids/utils.py

@@ -2,6 +2,11 @@
 
 import re
 import os
+from frozendict import frozendict
+
+
+# Monkeypatch to print out frozendicts *as if* they were dictionaries.
+frozendict.__repr__ = lambda s: repr({k: v for k, v in s.items()})
 
 
 def listify(obj):
@@ -10,6 +15,16 @@ def listify(obj):
     return obj if isinstance(obj, (list, tuple, type(None))) else [obj]
 
 
+def hashablefy(obj):
+    ''' Make dictionaries and lists hashable or raise. '''
+    if isinstance(obj, list):
+        return tuple([hashablefy(o) for o in obj])
+
+    if isinstance(obj, dict):
+        return frozendict({k: hashablefy(v) for k, v in obj.items()})
+    return obj
+
+
 def matches_entities(obj, entities, strict=False):
     ''' Checks whether an object's entities match the input. '''
     if strict and set(obj.entities.keys()) != set(entities.keys()):

setup.cfg

@@ -31,6 +31,7 @@ install_requires =
     bids-validator
     num2words
     click
+    frozendict
 tests_require =
     pytest >=3.3
     mock