Improve error messages for missing nodes

3 files changed, 8 insertions, 5 deletions

diff --git a/NEWS b/NEWS
index 02d4494..3eea7c2 100644
--- a/NEWS
+++ b/NEWS
@@ -15,6 +15,7 @@ Version UNRELEASED
   `NodeStore` and `NodeStoreMemory` now have a new first argument,
   `allow_writes`, to make them compatible with the `NodeStoreDisk`
   initialiser. Patch by Antoine Brenner.
+* Improved error messages for nodes that seem to be missing.
 
 Version 1.20121216
 ------------------
diff --git a/larch/nodestore.py b/larch/nodestore.py
index dd9b536..70bcc93 100644
--- a/larch/nodestore.py
+++ b/larch/nodestore.py
@@ -21,10 +21,8 @@ class NodeMissing(larch.Error):
 
     '''A node cannot be found from a NodeStore.'''
     
-    def __init__(self, node_store, node_id, error=None):
-        if error is None:
-            error_msg = ''
-        else:
+    def __init__(self, node_store, node_id, error=None, error_msg=''):
+        if error is not None:
             error_msg = (': %s: %s: %s' % 
                          (error.errno, error.strerror, error.filename))
         self.msg = ('Node %s cannot be found in the node store %s%s' % 
diff --git a/larch/nodestore_disk.py b/larch/nodestore_disk.py
index 6e8cd2f..dec41e1 100644
--- a/larch/nodestore_disk.py
+++ b/larch/nodestore_disk.py
@@ -258,7 +258,11 @@ class NodeStoreDisk(larch.NodeStore):
         if self.journal.exists(name):
             self.journal.remove(name)
         elif not got_it:
-            raise larch.NodeMissing(self.dirname, node_id)
+            raise larch.NodeMissing(
+                self.dirname, 
+                node_id, 
+                error_msg='attempted to remove node that is not '
+                    'in journal or in upload queue')
         
     def list_nodes(self):
         queued = self.upload_queue.list_ids()