MAX_FETCH_FILE_SIZE = 0 (no limit) trips the list zip-bomb guard too (#939)

list_fetch.py

@@ -217,6 +217,20 @@ def list_extract_dir(bot):
     return candidate
 
 
+def _fetch_file_size_budget():
+    """MAX_FETCH_FILE_SIZE, resolved the way dcc_fetch.py's own admission
+    check already reads it: 0 means no limit (#302), not a real zero-byte
+    ceiling. Read here rather than left as the raw setting because this
+    module uses the value twice - once as the zip-bomb sum cap in
+    _validate_zip_members(), once as the running extraction budget in
+    process_fetched_list_zip() - and a `budget` that starts at a literal 0
+    would fail the very first byte written, the same bug either call site
+    would have on its own (#937 was the sibling of this one, on
+    MAX_FETCH_LIST_FILE_SIZE)."""
+    raw = int(getattr(config, "MAX_FETCH_FILE_SIZE", 200 * 1024 * 1024))
+    return raw if raw > 0 else float("inf")
+
+
 def _validate_zip_members(infolist, extract_dir):
     """Check EVERY member before anything is extracted. Returns a short
     rejection reason string, or None if the whole archive is clear to
@@ -229,7 +243,7 @@ def _validate_zip_members(infolist, extract_dir):
                 f"{MAX_LIST_ZIP_ENTRIES} a real master-list archive should "
                 f"ever need (zip-bomb-shaped guard)")
 
-    max_total = int(getattr(config, "MAX_FETCH_FILE_SIZE", 200 * 1024 * 1024))
+    max_total = _fetch_file_size_budget()
     total_uncompressed = 0
     for info in infolist:
         if info.is_dir():
@@ -683,8 +697,7 @@ def _extract_and_locate_list_file(zip_path, extract_dir):
                 shutil.rmtree(platform_compat.long_path(extract_dir), ignore_errors=True)
                 return None, reason
 
-            max_total = int(getattr(config, "MAX_FETCH_FILE_SIZE", 200 * 1024 * 1024))
-            budget = max_total
+            budget = _fetch_file_size_budget()
             for info in infolist:
                 if info.is_dir():
                     continue

tests/test_list_fetch.py

@@ -207,8 +207,20 @@ def test_a_declared_total_size_over_the_cap_is_rejected_before_extracting(self):
 
         self.assertFalse(ok)
         self.assertIn("exceeds", reason)
-        self.assertNotIn("bigbot", config.fetched_bot_lists)
-        self.assertFalse(os.path.exists(list_fetch.list_extract_dir("bigbot")))
+
+    def test_zero_means_no_cap_on_the_declared_total_either(self):
+        """#937's sibling: MAX_FETCH_FILE_SIZE = 0 is "no limit" here too, not
+        a zero-byte zip-bomb ceiling that rejects any real list - and the same
+        value is the running extraction budget, so a fix that only touched the
+        sum check and left `budget` starting at a literal 0 would still fail
+        on the very first byte written."""
+        self.set_config(MAX_FETCH_FILE_SIZE=0)
+        big_txt = _list_txt() + ("!OtherBot Filler.flac  ::INFO:: 1.0MB\n" * 50)
+        _write_zip(self.zip_path, [("OtherBot-2026-08-27.txt", big_txt)])
+
+        ok, reason = list_fetch.process_fetched_list_zip("bigbot", self.zip_path)
+
+        self.assertTrue(ok, reason)
 
     def test_an_oversized_zip_on_disk_is_rejected_before_it_is_opened(self):
         """#162 finding #10, belt-to-braces half: MAX_LIST_ZIP_ENTRIES and the