added back drop_old_entries as well as a test case for it, only trigger it after a skip

dap/utils/sorter.py

@@ -18,7 +18,9 @@ class Sorter:
 
     def flush_ready(self):
         res = self._collect_contiguous_IDs()
-        self._skip_over_gap()
+        skipped = self._skip_over_gap()
+        if skipped:
+            self._drop_old_entries()
         return res
 
     def _collect_contiguous_IDs(self):
@@ -30,7 +32,16 @@ class Sorter:
         return res
 
     def _skip_over_gap(self):
-        self.next_ID = max(self.next_ID, self.max_ID - self.window)
+        threshold = self.max_ID - self.window
+        skip = self.next_ID < threshold
+        if skip:
+            self.next_ID = threshold
+        return skip
+
+    def _drop_old_entries(self):
+        for i in list(self.buffer):
+            if i < self.next_ID:
+                del self.buffer[i]
 
 
 
@@ -63,5 +74,28 @@ if __name__ == "__main__":
         exc = [(i, i) for i in exc]
         assert exc == ready, f"{exc} != {ready}"
 
+    assert sorter.buffer == {}
+
+
+    sorter = Sorter(window=5)
+
+    data = [
+        0, # this is sent -- small gap coming
+        2, # large gap coming -- this goes stale
+    ] + list(range(10, 17)) # this is sent
+
+    expected = [
+        [0],
+        [], [], [], [], [], [], []
+    ] + [list(range(10, 17))]
+
+    for ID, exc in zip(data, expected):
+        sorter.add(ID, ID)
+        ready = sorter.flush_ready()
+        exc = [(i, i) for i in exc]
+        assert exc == ready, f"{exc} != {ready}"
+
+    assert sorter.buffer == {}
+