From d4bdc36550ab75f38aba9de377acc6705f38f4c4 Mon Sep 17 00:00:00 2001
From: Guillaume Ayoub <guillaume.ayoub@kozea.fr>
Date: Tue, 13 Apr 2010 00:25:01 +0200
Subject: [PATCH] Report item modification to users in various cases.

---
 NEWS                 |  1 +
 radicale/__init__.py | 10 +++++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/NEWS b/NEWS
index 3dee09f..000dac1 100644
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,7 @@
 * Twisted dependency removed
 * Python 3 support
 * Real URLs for PUT and DELETE
+* Concurrent modification reported to users
 * Many bugs fixed by Roger Wenham
 
 
diff --git a/radicale/__init__.py b/radicale/__init__.py
index 89bc468..b1125eb 100644
--- a/radicale/__init__.py
+++ b/radicale/__init__.py
@@ -188,15 +188,19 @@ class CalendarHTTPHandler(server.BaseHTTPRequestHandler):
     def do_PUT(self):
         """Manage PUT request."""
         item = self._calendar.get_item(xmlutils.name_from_path(self.path))
-        if not item or self.headers.get("If-Match", item.etag) == item.etag:
-            # No item, no ETag precondition or precondition verified, put item
+        if (not item and not self.headers.get("If-Match")) or \
+                (item and self.headers.get("If-Match", item.etag) == item.etag):
+            # PUT allowed in 3 cases
+            # Case 1: No item and no ETag precondition: Add new item
+            # Case 2: Item and ETag precondition verified: Modify item
+            # Case 3: Item and no Etag precondition: Force modifying item
             ical_request = self._decode(
                 self.rfile.read(int(self.headers["Content-Length"])))
             xmlutils.put(self.path, ical_request, self._calendar)
 
             self.send_response(client.CREATED)
         else:
-            # ETag precondition not verified, do not put item
+            # PUT rejected in all other cases
             self.send_response(client.PRECONDITION_FAILED)
 
     @check_rights