[#434] metadata calls now require AVU fields to be nonzero-length strings

AVU add and set operations will henceforth require attribute and value arguments
to be nonzero-length and exactly of type str (ie. Python string).  Only the units
field may have a value that is zero-length or, equivalently, of type None.
(Semantically, either one is the same as omitting the units.)

If an irods.meta.iRODSMeta object is used in the call, the above restrictions
apply to the corresponding fields of that object.

Author: d-w-moore

irods/message/__init__.py

@@ -19,6 +19,9 @@
                                     IntegerProperty, LongProperty, ArrayProperty,
                                     SubmessageProperty)
 
+class Bad_AVU_Field(Exception):
+    pass
+
 _TUPLE_LIKE_TYPES = (tuple, list)
 
 def _qxml_server_version( var ):
@@ -670,9 +673,29 @@ class MetadataRequest(Message):
 
     def __init__(self, *args, **metadata_opts):
         super(MetadataRequest, self).__init__()
-        for i in range(len(args)):
-            if args[i]:
-                setattr(self, 'arg%d' % i, args[i])
+
+        NoneType = type(None)
+        def field_name(i) : return ("attribute", "value", "unit")[i-3]
+
+        # We now enforce these requirements of the scalars (ie. AVU fields) submitted to the metadata call:
+        #   * All fields must each be of type str, except that the units field can be the None object.
+        #   * Attribute and Value must be of type str (a Python string) as well as nonzero length.
+        for i,arg in enumerate(args):
+            error = None
+
+            # Raise usage error if any of the AVU fields (args 3 to 5 inclusive) do not meet the above constraints.
+            if i in (3,4,5):
+                if type(arg) not in ({str, UNICODE} if i<5 else {str, UNICODE, NoneType}):
+                    error = Bad_AVU_Field("AVU %s (%r) has incorrect type. AVU fields must be strings, except for units, which could be None." % (field_name(i),arg))
+                elif i<5 and not(arg):
+                    error = Bad_AVU_Field("AVU %s (%r) is zero-length." % (field_name(i), arg))
+            if error is not None:
+                raise error
+
+            # If there is no error, set the attribute in the request message.
+            if arg not in {None, b'', ''}:
+                setattr(self, 'arg%d' % i, arg)
+
         self.KeyValPair_PI = StringStringMap(metadata_opts)
 
     arg0 = StringProperty()

irods/test/meta_test.py

@@ -14,6 +14,8 @@
 from irods.session import iRODSSession
 from six.moves import range
 from six import PY3
+from irods.message import Bad_AVU_Field
+
 
 
 class TestMeta(unittest.TestCase):
@@ -442,6 +444,14 @@ def units():
                 if d: d.unlink(force = True)
                 helpers.remove_unused_metadata(session)
 
+    def test_nonstring_as_AVU_value_raises_an_error__issue_434(self):
+        with self.assertRaisesRegexp(Bad_AVU_Field,'incorrect type'):
+            self.coll.metadata.set("an_attribute",0)
+
+    def test_empty_string_as_AVU_value_raises_an_error__issue_434(self):
+        with self.assertRaisesRegexp(Bad_AVU_Field,'zero-length'):
+            self.coll.metadata.set("an_attribute","")
+
 if __name__ == '__main__':
     # let the tests find the parent irods lib
     sys.path.insert(0, os.path.abspath('../..'))