Fix vt=0 being ignored in read() method (#11)

* feat: add set_vt_method and usage docs

* test: add test for set_vt method

* Initial plan

* Fix bug: vt=0 should be valid visibility timeout value

Added check for `vt is None` in the read() method to properly handle vt=0.
Previously, vt=0 would be treated as falsy and would default to self.vt (30 seconds).
Now vt=0 correctly sets the visibility timeout to 0 seconds as expected.

Also added test case to verify vt=0 works correctly.

Co-authored-by: jason810496 <[email protected]>

---------

Co-authored-by: jason810496 <[email protected]>
Co-authored-by: LIU ZHE YOU <[email protected]>
Co-authored-by: copilot-swe-agent[bot] <[email protected]>

Author: Copilot

pgmq_sqlalchemy/queue.py

@@ -573,6 +573,8 @@ def read(self, queue_name: str, vt: Optional[int] = None) -> Optional[Message]:
 
 
         """
+        if vt is None:
+            vt = self.vt
         if self.is_async:
             return self.loop.run_until_complete(self._read_async(queue_name, vt))
         return self._read_sync(queue_name, vt)

tests/test_queue.py

@@ -162,6 +162,21 @@ def test_send_and_read_msg_with_vt_and_delay(pgmq_setup_teardown: PGMQ_WITH_QUEU
     assert msg_read.msg_id == msg_id
 
 
+def test_send_and_read_msg_with_vt_zero(pgmq_setup_teardown: PGMQ_WITH_QUEUE):
+    """Test that vt=0 works correctly and message becomes visible immediately."""
+    pgmq, queue_name = pgmq_setup_teardown
+    msg = MSG
+    msg_id: int = pgmq.send(queue_name, msg)
+    # Read with vt=0 means message should be immediately visible again
+    msg_read = pgmq.read(queue_name, vt=0)
+    assert msg_read.message == msg
+    assert msg_read.msg_id == msg_id
+    # Message should be visible immediately (no waiting)
+    msg_read = pgmq.read(queue_name)
+    assert msg_read.message == msg
+    assert msg_read.msg_id == msg_id
+
+
 def test_read_empty_queue(pgmq_setup_teardown: PGMQ_WITH_QUEUE):
     pgmq, queue_name = pgmq_setup_teardown
     msg_read = pgmq.read(queue_name)