Enforce nonzero connections in PoolBuilder

src/pool.rs

@@ -78,9 +78,16 @@ impl PoolBuilder {
 
     /// Specify the number of sqlite connections to open as part of the pool.
     ///
-    /// Defaults to the number of logical CPUs of the current system.
+    /// Defaults to the number of logical CPUs of the current system. Values
+    /// less than `1` are clamped to `1`.
+    ///
+    /// ```
+    /// use async_sqlite::PoolBuilder;
+    ///
+    /// let builder = PoolBuilder::new().num_conns(2);
+    /// ```
     pub fn num_conns(mut self, num_conns: usize) -> Self {
-        self.num_conns = Some(num_conns);
+        self.num_conns = Some(num_conns.max(1));
         self
     }
 

tests/tests.rs

@@ -84,6 +84,7 @@ async_test!(test_journal_mode);
 async_test!(test_concurrency);
 async_test!(test_pool);
 async_test!(test_pool_conn_for_each);
+async_test!(test_pool_num_conns_zero_clamps);
 
 async fn test_journal_mode() {
     let tmp_dir = tempfile::tempdir().unwrap();
@@ -227,3 +228,15 @@ async fn test_pool_conn_for_each() {
     // cleanup
     pool.close().await.expect("closing client conn");
 }
+
+async fn test_pool_num_conns_zero_clamps() {
+    let tmp_dir = tempfile::tempdir().unwrap();
+    let pool = PoolBuilder::new()
+        .path(tmp_dir.path().join("clamp.db"))
+        .num_conns(0)
+        .open()
+        .await
+        .expect("pool unable to be opened");
+    let results = pool.conn_for_each(|_| Ok(())).await;
+    assert_eq!(results.len(), 1);
+}