Merge pull request #72 from templateflow/fix/import-bids-error

FIX: layout is ``None`` when PyBIDS not correctly installed

Author: oesteban

templateflow/api.py

@@ -4,9 +4,10 @@
 import re
 import sys
 
-from .conf import TF_LAYOUT, TF_S3_ROOT, TF_USE_DATALAD
+from .conf import TF_LAYOUT, TF_S3_ROOT, TF_USE_DATALAD, requires_layout
 
 
+@requires_layout
 def get(template, raise_empty=False, **kwargs):
     """
     Fetch one file from one particular template.
@@ -111,9 +112,10 @@ def get(template, raise_empty=False, **kwargs):
     return out_file
 
 
+@requires_layout
 def templates(**kwargs):
     """
-    Returns a list of available templates.
+    Return a list of available templates.
 
     Keyword Arguments
     -----------------
@@ -140,6 +142,7 @@ def templates(**kwargs):
     return sorted(TF_LAYOUT.get_templates(**kwargs))
 
 
+@requires_layout
 def get_metadata(template):
     """
     Fetch one file from one template.
@@ -155,7 +158,6 @@ def get_metadata(template):
     'Linear ICBM Average Brain (ICBM152) Stereotaxic Registration Model'
 
     """
-
     tf_home = Path(TF_LAYOUT.root)
     filepath = tf_home / ("tpl-%s" % template) / "template_description.json"
 

templateflow/conf/__init__.py

@@ -2,6 +2,8 @@
 from os import getenv
 from warnings import warn
 from pathlib import Path
+from contextlib import suppress
+from functools import wraps
 
 TF_DEFAULT_HOME = Path.home() / ".cache" / "templateflow"
 TF_HOME = Path(getenv("TEMPLATEFLOW_HOME", str(TF_DEFAULT_HOME)))
@@ -16,6 +18,20 @@
 )
 TF_CACHED = True
 
+
+def requires_layout(func):
+    """Decorate function to ensure ``TF_LAYOUT`` is correctly initiated."""
+    @wraps(func)
+    def wrapper(*args, **kwargs):
+        from templateflow.conf import TF_LAYOUT
+
+        if TF_LAYOUT is None:
+            from bids import __version__
+            raise RuntimeError(f"A layout with PyBIDS <{__version__}> could not be initiated")
+        return func(*args, **kwargs)
+    return wrapper
+
+
 if not TF_HOME.exists() or not list(TF_HOME.iterdir()):
     TF_CACHED = False
     warn(
@@ -87,7 +103,7 @@ def _update_datalad():
 
 
 def init_layout():
-    from .bids import Layout
+    from templateflow.conf.bids import Layout
     from bids.layout.index import BIDSLayoutIndexer
 
     global TF_LAYOUT
@@ -109,7 +125,5 @@ def init_layout():
     )
 
 
-try:
+with suppress(ImportError):
     init_layout()
-except ImportError:
-    pass

templateflow/conf/tests/test_conf.py

@@ -90,3 +90,29 @@ def test_layout(monkeypatch, tmp_path):
     assert lines[0] == "TemplateFlow Layout"
     assert lines[1] == " - Home: %s" % tfc.TF_HOME
     assert lines[2].startswith(" - Templates:")
+
+
+def test_layout_errors(monkeypatch):
+    """Check regression of #71."""
+    import sys
+    import builtins
+    from importlib import __import__ as oldimport
+
+    @tfc.requires_layout
+    def myfunc():
+        return "okay"
+
+    def mock_import(name, globals=None, locals=None, fromlist=tuple(), level=0):
+        if name == "bids":
+            raise ModuleNotFoundError
+        return oldimport(name, globals=globals, locals=locals, fromlist=fromlist, level=level)
+
+    with monkeypatch.context() as m:
+        m.setattr(tfc, "TF_LAYOUT", None)
+        with pytest.raises(RuntimeError):
+            myfunc()
+
+        m.delitem(sys.modules, "bids")
+        m.setattr(builtins, "__import__", mock_import)
+        with pytest.raises(ImportError):
+            myfunc()