Allow CapacityLimiter to have zero total_tokens

Author: AbduazizZiyodov

src/trio/_sync.py

@@ -251,8 +251,8 @@ def total_tokens(self) -> int | float:
     def total_tokens(self, new_total_tokens: int | float) -> None:  # noqa: PYI041
         if not isinstance(new_total_tokens, int) and new_total_tokens != math.inf:
             raise TypeError("total_tokens must be an int or math.inf")
-        if new_total_tokens < 1:
-            raise ValueError("total_tokens must be >= 1")
+        if new_total_tokens < 0:
+            raise ValueError("total_tokens must be >= 0")
         self._total_tokens = new_total_tokens
         self._wake_waiters()
 

src/trio/_tests/test_sync.py

@@ -49,9 +49,10 @@ async def child() -> None:
 
 
 async def test_CapacityLimiter() -> None:
+    assert CapacityLimiter(0).total_tokens == 0
     with pytest.raises(TypeError):
         CapacityLimiter(1.0)
-    with pytest.raises(ValueError, match=r"^total_tokens must be >= 1$"):
+    with pytest.raises(ValueError, match=r"^total_tokens must be >= 0$"):
         CapacityLimiter(-1)
     c = CapacityLimiter(2)
     repr(c)  # smoke test
@@ -139,10 +140,10 @@ async def test_CapacityLimiter_change_total_tokens() -> None:
     with pytest.raises(TypeError):
         c.total_tokens = 1.0
 
-    with pytest.raises(ValueError, match=r"^total_tokens must be >= 1$"):
-        c.total_tokens = 0
+    with pytest.raises(ValueError, match=r"^total_tokens must be >= 0$"):
+        c.total_tokens = -1
 
-    with pytest.raises(ValueError, match=r"^total_tokens must be >= 1$"):
+    with pytest.raises(ValueError, match=r"^total_tokens must be >= 0$"):
         c.total_tokens = -10
 
     assert c.total_tokens == 2