Fix unbounded Queue growth when the queue never drains

src/queue.js

@@ -9,10 +9,10 @@ function Queue(initial = []) {
       return xs.length - index
     },
     remove: (x) => {
-      const index = xs.indexOf(x)
-      return index === -1
+      const i = xs.indexOf(x, index)
+      return i === -1
         ? null
-        : (xs.splice(index, 1), x)
+        : (xs.splice(i, 1), x)
     },
     push: (x) => (xs.push(x), x),
     shift: () => {
@@ -21,6 +21,9 @@ function Queue(initial = []) {
       if (index === xs.length) {
         index = 0
         xs = []
+      } else if (index > 64 && index * 2 >= xs.length) {
+        xs = xs.slice(index)
+        index = 0
       } else {
         xs[index - 1] = undefined
       }

tests/index.js

@@ -6,6 +6,7 @@ import fs from 'fs'
 import crypto from 'crypto'
 
 import postgres from '../src/index.js'
+import Queue from '../src/queue.js'
 const delay = ms => new Promise(r => setTimeout(r, ms))
 
 const rel = x => new URL(x, import.meta.url)
@@ -2719,3 +2720,26 @@ t('query during copy error', async() => {
     await sql`drop table test`
   ]
 })
+
+t('Queue does not grow when never drained', async() => {
+  let size = 0
+  const q = Queue(new class extends Array { // Queue copies this with .slice(), which keeps the subclass
+    push(x) {
+      const length = super.push(x)
+      size = Math.max(size, length)
+      return length
+    }
+  }())
+
+  q.push('a')
+  q.push('b')
+  q.push('c')
+  for (let i = 0; i < 10000; i++)
+    q.push(q.shift())
+
+  const result = [q.length, q.remove('x'), q.shift(), q.remove('a'), q.length, q.shift(), q.length]
+  q.push('d')
+  q.push('e')
+  result.push(q.remove('d'), q.shift(), size > 0 && size < 1000 || size)
+  return ['3,,b,a,1,c,0,d,e,true', result.join()]
+})