HTTPCLIENT-2437: LaxConnPool fails expired lease requests queued behind a live one

httpcore5/src/main/java/org/apache/hc/core5/pool/LaxConnPool.java

@@ -642,6 +642,9 @@ public void enumAvailable(final Callback<PoolEntry<T, C>> callback) {
             }
             releaseSeqNum.incrementAndGet();
             servicePendingRequests(RequestServiceStrategy.ALL);
+            // servicePendingRequests stops at the first request it cannot serve,
+            // so expired requests queued behind it would stay pending.
+            validatePendingRequests();
         }
 
         public void enumLeased(final Callback<PoolEntry<T, C>> callback) {

httpcore5/src/test/java/org/apache/hc/core5/pool/TestPoolPendingRequestExpiry.java

@@ -26,6 +26,7 @@
  */
 package org.apache.hc.core5.pool;
 
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -92,6 +93,33 @@ void closeIdleFailsExpiredPendingRequest(final PoolConcurrencyPolicy policy) thr
         }
     }
 
+    @ParameterizedTest
+    @EnumSource(PoolConcurrencyPolicy.class)
+    void closeExpiredFailsExpiredRequestQueuedBehindLiveRequest(final PoolConcurrencyPolicy policy) throws Exception {
+        final TestingClock clock = new TestingClock(0L);
+        final ManagedConnPool<String, PoolTestSupport.DummyConn> pool =
+                PoolTestSupport.createPool(policy, 1, 1, clock);
+        try {
+            final PoolEntry<String, PoolTestSupport.DummyConn> leased =
+                    pool.lease("r1", null, Timeout.ofSeconds(1), null).get(1, TimeUnit.SECONDS);
+            assertNotNull(leased);
+            final Future<PoolEntry<String, PoolTestSupport.DummyConn>> live =
+                    pool.lease("r1", null, Timeout.ofMinutes(1), null);
+            final Future<PoolEntry<String, PoolTestSupport.DummyConn>> expired =
+                    pool.lease("r1", null, Timeout.ofMilliseconds(100), null);
+
+            clock.advanceMillis(10_000L);
+            pool.closeExpired();
+
+            final ExecutionException ex = assertThrows(ExecutionException.class,
+                    () -> expired.get(5, TimeUnit.SECONDS));
+            assertInstanceOf(TimeoutException.class, ex.getCause());
+            assertFalse(live.isDone(), "Request that has not expired must stay pending");
+        } finally {
+            pool.close(CloseMode.IMMEDIATE);
+        }
+    }
+
     @ParameterizedTest
     @EnumSource(PoolConcurrencyPolicy.class)
     void expiredPendingRequestIsDoneAfterEviction(final PoolConcurrencyPolicy policy) throws Exception {