Add JsonPatchConflict for patch conflicts

This is necessary in order to differentiate between
general processing errors e.g. bad operation and
conflicts between the patch and the state of the
data the patch is being applied to.

1 files changed, 11 insertions, 7 deletions

diff --git a/jsonpatch.py b/jsonpatch.py
index d75e27c..7ada8e3 100644
--- a/jsonpatch.py
+++ b/jsonpatch.py
@@ -47,6 +47,10 @@ class JsonPatchException(Exception):
     pass
 
 
+class JsonPatchConflict(JsonPatchException):
+    pass
+
+
 def apply_patch(doc, patch):
     """
     >>> obj = { 'baz': 'qux', 'foo': 'bar' }
@@ -139,7 +143,7 @@ class PatchOperation(object):
                 continue
 
         if must_exist:
-            raise JsonPatchException('key %s not found' % loc_part)
+            raise JsonPatchConflict('key %s not found' % loc_part)
         else:
             return obj, part_variants[0]
 
@@ -191,18 +195,18 @@ class AddOperation(PatchOperation):
 
         if isinstance(subobj, list):
             if part > len(subobj) or part < 0:
-                raise JsonPatchException("can't insert outside of list")
+                raise JsonPatchConflict("can't insert outside of list")
 
             subobj.insert(part, value)
 
         elif isinstance(subobj, dict):
             if part in subobj:
-                raise JsonPatchException("object '%s' already exists" % part)
+                raise JsonPatchConflict("object '%s' already exists" % part)
 
             subobj[part] = value
 
         else:
-            raise JsonPatchException("can't add to type '%s'" % subobj.__class__.__name__)
+            raise JsonPatchConflict("can't add to type '%s'" % subobj.__class__.__name__)
 
 
 class ReplaceOperation(PatchOperation):
@@ -221,13 +225,13 @@ class ReplaceOperation(PatchOperation):
 
         if isinstance(subobj, list):
             if part > len(subobj) or part < 0:
-                raise JsonPatchException("can't replace outside of list")
+                raise JsonPatchConflict("can't replace outside of list")
 
         elif isinstance(subobj, dict):
             if not part in subobj:
-                raise JsonPatchException("can't replace non-existant object '%s'" % part)
+                raise JsonPatchConflict("can't replace non-existant object '%s'" % part)
 
         else:
-            raise JsonPatchException("can't replace in type '%s'" % subobj.__class__.__name__)
+            raise JsonPatchConflict("can't replace in type '%s'" % subobj.__class__.__name__)
 
         subobj[part] = value