fix: task 10 + review fix #1 — thread safety and sleep bug

Fix #1: Don't sleep after the final exhausted retry attempt in
_graph_request(). The sleep on the last iteration was pure overhead —
the loop exits immediately after, so the caller just waited an extra
backoff period for no reason. Guard with attempt < _MAX_RETRIES - 1.

Task 10: Add threading.Lock (_edits_lock) for all compound operations
on active_edits, which is accessed from both the UI thread and
background edit threads:
- __init__: declare self._edits_lock = threading.Lock()
- open_file: snapshot already_editing and at_limit under the lock,
  then release before showing blocking UI dialogs
- process_file: wrap initial dict assignment, waiting=True, the
  in-check+waiting=False, and in-check+del under the lock
- on_done_editing_clicked: lock the items() snapshot used to build
  waiting_files, preventing iteration over a dict being mutated

Add 8 new unit tests (1 for Fix #1 sleep count, 7 for Task 10 lock).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sharepoint_browser.py

@@ -92,8 +92,9 @@ def _graph_request(method, url, **kwargs):
         res = requests.request(method, url, **kwargs)
         if res.status_code not in _RETRY_STATUSES:
             return res
-        retry_after = int(res.headers.get("Retry-After", 2 ** attempt))
-        time.sleep(min(retry_after, 60))
+        if attempt < _MAX_RETRIES - 1:  # Don't sleep after the final attempt
+            retry_after = int(res.headers.get("Retry-After", 2 ** attempt))
+            time.sleep(min(retry_after, 60))
     return res  # Return last response after exhausting retries
 
 settings = load_settings()
@@ -697,6 +698,7 @@ class SharePointApp(wx.Frame):
         self.tree_root = None
         self.is_navigating_back = False
         self.active_edits = {} # item_id -> { "name": name, "event": Event, "waiting": bool }
+        self._edits_lock = threading.Lock()
         self.favorites = settings.get("favorites", [])
         self.fav_visible = settings.get("fav_visible", True)
         self.sort_col = 0 # Default (Navn)
@@ -1404,7 +1406,8 @@ class SharePointApp(wx.Frame):
         wx.CallAfter(_do)
 
     def on_done_editing_clicked(self, event):
-        waiting_files = [fid for fid, d in self.active_edits.items() if d.get("waiting")]
+        with self._edits_lock:
+            waiting_files = [fid for fid, d in self.active_edits.items() if d.get("waiting")]
         if not waiting_files:
             return
             
@@ -2253,12 +2256,16 @@ class SharePointApp(wx.Frame):
         item_id = item['id']
         file_name = item['name']
         drive_id = item['drive_id']
-        
-        if item_id in self.active_edits:
+
+        with self._edits_lock:
+            already_editing = item_id in self.active_edits
+            at_limit = len(self.active_edits) >= 10
+
+        # UI dialogs are called outside the lock to avoid holding it during blocking calls
+        if already_editing:
             self.show_info(f"'{file_name}' er allerede ved at blive redigeret.", wx.ICON_INFORMATION)
             return
-
-        if len(self.active_edits) >= 10:
+        if at_limit:
             wx.MessageBox("Du kan kun have 10 filer åbne til redigering ad gangen.", "Maksimum grænse nået", wx.OK | wx.ICON_WARNING)
             return
 
@@ -2295,7 +2302,8 @@ class SharePointApp(wx.Frame):
         if not self.ensure_valid_token(): return
         
         edit_event = threading.Event()
-        self.active_edits[item_id] = {"name": file_name, "event": edit_event, "waiting": False}
+        with self._edits_lock:
+            self.active_edits[item_id] = {"name": file_name, "event": edit_event, "waiting": False}
         self.update_edit_ui()
         
         try:
@@ -2382,13 +2390,15 @@ class SharePointApp(wx.Frame):
             else:
                 self.set_status(self.get_txt("msg_waiting_for_file", name=file_name))
                 edit_event.clear()
-                self.active_edits[item_id]["waiting"] = True
+                with self._edits_lock:
+                    self.active_edits[item_id]["waiting"] = True
                 self.update_edit_ui()
-                
+
                 edit_event.wait()
-                
-                if item_id in self.active_edits:
-                    self.active_edits[item_id]["waiting"] = False
+
+                with self._edits_lock:
+                    if item_id in self.active_edits:
+                        self.active_edits[item_id]["waiting"] = False
                 self.update_edit_ui()
 
             # 4. Tjek om noget er ændret
@@ -2448,8 +2458,9 @@ class SharePointApp(wx.Frame):
                 logger.info(f"Rydder op: Kalder discardCheckout for {file_name}...")
                 _graph_request("POST", f"{base_url}/discardCheckout", headers=self.headers, timeout=30)
                 
-            if item_id in self.active_edits:
-                del self.active_edits[item_id]
+            with self._edits_lock:
+                if item_id in self.active_edits:
+                    del self.active_edits[item_id]
             self.update_edit_ui()
 
 if __name__ == "__main__":