Make sure member count is accurate when writer rejoining (#167)

* add test for removing and rejoining

* removed writer does not count as tracked

lib/system.js

@@ -305,11 +305,11 @@ module.exports = class SystemView extends ReadyResource {
       cas (older, newer) {
         if (older === null) return true
 
-        wasTracked = true
-
         const o = older.value
         const n = newer.value
 
+        if (!o.isRemoved) wasTracked = true
+
         if (length === 0 && o.length) length = o.length
 
         return o.isRemoved !== n.isRemoved || o.isIndexer !== n.isIndexer || o.length !== n.length

test/basic.js

@@ -1088,6 +1088,31 @@ test('basic - remove writer', async t => {
   t.is(b.system.members, c.system.members)
 })
 
+test('basic - remove and rejoin writer', async t => {
+  const { bases } = await create(2, t, { apply: applyWithRemove, open: null })
+  const [a, b] = bases
+
+  await addWriter(a, b, false)
+  await confirm([a, b])
+
+  t.is(a.system.members, 2)
+
+  await a.append({ remove: b4a.toString(b.local.key, 'hex') })
+  await confirm([a, b])
+
+  t.is(a.system.members, 1)
+
+  await addWriter(a, b, false)
+  await confirm([a, b])
+
+  t.is(a.system.members, 2)
+
+  await a.append({ remove: b4a.toString(b.local.key, 'hex') })
+  await confirm([a, b])
+
+  t.is(a.system.members, 1)
+})
+
 test('basic - non-indexer writer removes themselves', async t => {
   const { bases } = await create(2, t, { apply: applyWithRemove, open: null })
   const [a, b] = bases