Metadata blacklist (#279)

* bugfix blacklist=None and add respecting blacklist

* adding how to circumvent blacklisting

* Update docs/source/faq.rst

Co-authored-by: qubixes <44498096+qubixes@users.noreply.github.com>

* refined

---------

Co-authored-by: qubixes <44498096+qubixes@users.noreply.github.com>

docs/source/faq.rst

@@ -85,10 +85,23 @@ Warnings can also be switched off through python's `warnings` package:
 
 .. code-block:: python
 
-   import warnings
-   warnings.filterwarnings("ignore")
+	import warnings
+	warnings.filterwarnings("ignore")
+
 
 **My metadata with keys starting with `org_` do not show up in the iBridges metadata.**
 ---------------------------------------------------------------------------------------
 
-iBridges **does not show** metadata that contain a key starting with the prefix `org_`. This is due to data security reasons on `Yoda systems <https://github.com/iBridges-for-iRODS/yoda>`__.
+By default, iBridges **does not show** metadata that contain a key starting with the prefix `org_`. This is due to data security reasons on `Yoda systems <https://github.com/UtrechtUniversity/yoda>`__.
+
+You can omit this by the following code:
+
+.. code-block:: python
+
+    from ibridges.meta import MetaData
+    
+    # collections
+    meta = MetaData(IrodsPath(session, "~", "my_coll").collection, blacklist=None)
+    # data objects
+    meta = MetaData(IrodsPath(session, "~", "my_obj").dataobject, blacklist=None)
+    print(meta)

ibridges/meta.py

@@ -58,8 +58,9 @@ def __iter__(self) -> Iterator:
         """Iterate over all metadata key/value/units triplets."""
         if self.blacklist is None:
             yield from self.item.metadata.items()
+            return
         for meta in self.item.metadata.items():
-            if re.match(self.blacklist, meta.name) is None:
+            if self.blacklist and re.match(self.blacklist, meta.name) is None:
                 yield meta
             else:
                 warnings.warn(f"Ignoring metadata entry with value {meta.name}, because it matches "
@@ -148,6 +149,9 @@ def add(self, key: str, value: str, units: Optional[str] = None):
         try:
             if (key, value, units) in self:
                 raise ValueError("ADD META: Metadata already present")
+            if self.blacklist:
+                if re.match(self.blacklist, key):
+                    raise ValueError(f"ADD META: Key must not start with {self.blacklist}.")
             self.item.metadata.add(key, value, units)
         except irods.exception.CAT_NO_ACCESS_PERMISSION as error:
             raise PermissionError("UPDATE META: no permissions") from error