fix: resolve reserve() hang with fetch_types disabled

src/connection.js

@@ -564,10 +564,16 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
         return fetchArrayTypes()
       }
 
-      initial && !initial.reserve && execute(initial)
-      options.shared.retries = retries = 0
+      if (!initial.reserve) {
+        execute(initial)
+        options.shared.retries = retries = 0
+        initial = null
+        return
+      }
+
+      // `fetch_types: false` with a queued `reserve()` — there is nothing to
+      // execute, so fall through and let `onopen(connection)` below resolve it.
       initial = null
-      return
     }
 
     while (sent.length && (query = sent.shift()) && (query.active = true, query.cancelled))

tests/index.js

@@ -2707,6 +2707,16 @@ t('Ensure reserve on query throws proper error', async() => {
   ]
 })
 
+t('reserve with fetch_types: false on a cold pool', async() => {
+  const sql = postgres({ ...options, fetch_types: false }) // eslint-disable-line
+  const reserved = await sql.reserve()
+  const [{ x }] = await reserved`select 1 as x`
+  reserved.release()
+  await sql.end()
+
+  return [1, x]
+})
+
 t('query during copy error', async() => {
   const sql = postgres(options) // eslint-disable-line
   await sql`create table test (id serial primary key, name text)`