Make stub server fail hard on OS errors

boltstub/__init__.py

@@ -235,16 +235,16 @@ def play(self):
                     # `try_skip_to_end` being called from the interrupt handler
                     # in `__main__.py` which spawns a new thread. Without this
                     # `sleep`, the main thread that keeps calling
-                    # `script.consume` only releases Script's internal lock  so
-                    # briefly that `try_skip_to_end` hangs unnecessarily long
+                    # `script.consume` only releases Script's internal lock so
+                    # briefly that `try_skip_to_end` can't reliably acquire it
+                    # thus hanging unnecessarily long.
                     time.sleep(0.000001)
                     continue
         except OSError as e:
-            # It's likely the client has gone away, so we can
-            # safely drop out and silence the error. There's no
-            # point in flagging a broken client from a test helper.
             self.log("S: <BROKEN> %r", e)
-            return
+            self.script.try_skip_to_end(self.channel)
+            if not self.script.done(self.channel):
+                raise
         self.log("Script finished")
 
     def try_skip_to_end(self):

boltstub/parsing.py

@@ -1213,14 +1213,10 @@ def has_deterministic_end(self) -> bool:
         return self.blocks[-1].has_deterministic_end()
 
     def init(self, channel):
-        while True:
+        while self.index < len(self.blocks):
             block = self.blocks[self.index]
             block.init(channel)
-            if (
-                not block.has_deterministic_end()
-                or not block.done(channel)
-                or self.index + 1 >= len(self.blocks)
-            ):
+            if not block.has_deterministic_end() or not block.done(channel):
                 break
             self.index += 1
 

boltstub/tests/test_integration.py

@@ -496,10 +496,17 @@ def test_restarting(server_factory, restarting, concurrent,
         "!: ALLOW CONCURRENT\n" if concurrent else "",
     )
 
-    server = server_factory(parse(script))
+    if restarting and concurrent:
+        with pytest.warns(
+            Warning, match="concurrent scripts are implicitly restarting"
+        ):
+            server = server_factory(parse(script))
+    else:
+        server = server_factory(parse(script))
+
     for i in range(3):
         if i > 0 and not (restarting or concurrent):
-            with pytest.raises((ConnectionError, OSError, BrokenSocket)):
+            with pytest.raises((OSError, BrokenSocket)):
                 con = connection_factory("localhost", 7687)
                 con.write(b"\x60\x60\xb0\x17")
                 con.write(server_version_to_version_request((4, 3)))