RF: copy input parameters on header creation

The input parameters are small, and it is easy to get confused when
using the mutable input parameters elsewhere, so copy the input dict,
array so each header has their own copy.

Author: matthew-brett

nibabel/parrec.py

@@ -513,8 +513,8 @@ def __init__(self, info, image_defs, permit_truncated=False):
             If True, a warning is emitted instead of an error when a truncated
             recording is detected.
         """
-        self.general_info = info
-        self.image_defs = image_defs
+        self.general_info = info.copy()
+        self.image_defs = image_defs.copy()
         _truncation_checks(info, image_defs, permit_truncated)
         # charge with basic properties to be able to use base class
         # functionality

nibabel/tests/test_parrec.py

@@ -140,12 +140,10 @@ def test_orientation():
     hdr = PARRECHeader(HDR_INFO, HDR_DEFS)
     assert_array_equal(HDR_DEFS['slice orientation'], 1)
     assert_equal(hdr.get_slice_orientation(), 'transverse')
-    hdr_defc = HDR_DEFS.copy()
-    hdr = PARRECHeader(HDR_INFO, hdr_defc)
+    hdr_defc = hdr.image_defs
     hdr_defc['slice orientation'] = 2
     assert_equal(hdr.get_slice_orientation(), 'sagittal')
     hdr_defc['slice orientation'] = 3
-    hdr = PARRECHeader(HDR_INFO, hdr_defc)
     assert_equal(hdr.get_slice_orientation(), 'coronal')
 
 
@@ -357,3 +355,16 @@ def test__get_uniqe_image_defs():
     assert_raises(PARRECError, uip, 'image angulation')
     # This one differs from the outset
     assert_raises(PARRECError, uip, 'slice number')
+
+
+def test_copy_on_init():
+    # Test that input dict / array gets copied when making header
+    hdr = PARRECHeader(HDR_INFO, HDR_DEFS)
+    assert_false(hdr.general_info is HDR_INFO)
+    hdr.general_info['max_slices'] = 10
+    assert_equal(hdr.general_info['max_slices'], 10)
+    assert_equal(HDR_INFO['max_slices'], 9)
+    assert_false(hdr.image_defs is HDR_DEFS)
+    hdr.image_defs['image pixel size'] = 8
+    assert_array_equal(hdr.image_defs['image pixel size'], 8)
+    assert_array_equal(HDR_DEFS['image pixel size'], 16)