fix: validate pool min_size/max_size to prevent silent hangs

ConnectionPool now rejects min_size > max_size, min_size < 0, and
max_size < 1 with clear ValueError messages. Previously, min_size
greater than max_size caused initialize() to hang forever because
the internal queue would fill up.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqliteclient/pool.py

@@ -32,6 +32,15 @@ def __init__(
             max_size: Maximum connections allowed
             timeout: Connection timeout
         """
+        if min_size < 0:
+            raise ValueError(f"min_size must be non-negative, got {min_size}")
+        if max_size < 1:
+            raise ValueError(f"max_size must be at least 1, got {max_size}")
+        if min_size > max_size:
+            raise ValueError(
+                f"min_size ({min_size}) must not exceed max_size ({max_size})"
+            )
+
         self._addresses = addresses
         self._database = database
         self._min_size = min_size

tests/test_pool.py

@@ -10,6 +10,18 @@
 
 
 class TestConnectionPool:
+    def test_min_size_greater_than_max_size_raises(self) -> None:
+        with pytest.raises(ValueError, match="min_size.*must not exceed.*max_size"):
+            ConnectionPool(["localhost:9001"], min_size=5, max_size=2)
+
+    def test_negative_min_size_raises(self) -> None:
+        with pytest.raises(ValueError, match="min_size.*non-negative"):
+            ConnectionPool(["localhost:9001"], min_size=-1)
+
+    def test_zero_max_size_raises(self) -> None:
+        with pytest.raises(ValueError, match="max_size.*at least 1"):
+            ConnectionPool(["localhost:9001"], max_size=0)
+
     def test_init(self) -> None:
         pool = ConnectionPool(
             ["localhost:9001", "localhost:9002"],