Add opts.persistentKey (to avoid writing key to disk)

index.js

@@ -25,6 +25,7 @@ module.exports = class Corestore extends EventEmitter {
     this.cores = root ? root.cores : new Map()
     this.cache = !!opts.cache
     this.primaryKey = opts.primaryKey || null
+    this.persistentKey = opts.persistentKey !== false
 
     this._keyStorage = null
     this._namespace = opts.namespace || DEFAULT_NAMESPACE
@@ -90,7 +91,7 @@ module.exports = class Corestore extends EventEmitter {
         if (err && err.code !== 'ENOENT') return reject(err)
         if (err || st.size < 32 || this._overwrite) {
           const key = this.primaryKey || crypto.randomBytes(32)
-          return this._keyStorage.write(0, key, err => {
+          return this._keyStorage.write(0, this.persistentKey ? key : b4a.alloc(0), err => {
             if (err) return reject(err)
             return resolve(key)
           })

test/all.js

@@ -5,6 +5,7 @@ const os = require('os')
 const path = require('path')
 const b4a = require('b4a')
 const sodium = require('sodium-universal')
+const fsp = require('fs/promises')
 
 const Corestore = require('..')
 
@@ -482,6 +483,68 @@ test('core-open and core-close events', async function (t) {
   t.is(closed, 2)
 })
 
+test('persistent primary key', async function (t) {
+  const dir = tmpdir()
+
+  const store = new Corestore(dir)
+  await store.ready()
+
+  try {
+    const store2 = new Corestore(dir, { persistentKey: false })
+    await store2.ready()
+    t.fail('should have failed')
+  } catch (error) {
+    t.is(error.code, 'ELOCKED', error.code)
+  }
+
+  await store.close()
+
+  const primaryKeyFile = await fsp.readFile(path.join(dir, 'primary-key'))
+  t.alike(primaryKeyFile, store.primaryKey)
+})
+
+test('non-persistent primary key', async function (t) {
+  const dir = tmpdir()
+
+  const store = new Corestore(dir, { persistentKey: false })
+  await store.ready()
+
+  t.is(store.primaryKey.length, 32)
+  t.unlike(store.primaryKey, b4a.alloc(32))
+
+  try {
+    const store2 = new Corestore(dir, { persistentKey: false })
+    await store2.ready()
+    t.fail('should have failed')
+  } catch (error) {
+    t.is(error.code, 'ELOCKED', error.code)
+  }
+
+  await store.close()
+
+  const primaryKeyFile = await fsp.readFile(path.join(dir, 'primary-key'))
+  t.alike(primaryKeyFile, b4a.alloc(0))
+})
+
+test('re open with non-persistent primary key', async function (t) {
+  const dir = tmpdir()
+
+  const key = randomBytes(32)
+
+  const store = new Corestore(dir, { primaryKey: key, persistentKey: false })
+  await store.ready()
+  t.alike(store.primaryKey, key)
+  await store.close()
+
+  const store2 = new Corestore(dir, { persistentKey: false })
+  await store2.ready()
+  t.unlike(store2.primaryKey, key)
+  await store2.close()
+
+  const primaryKeyFile = await fsp.readFile(path.join(dir, 'primary-key'))
+  t.alike(primaryKeyFile, b4a.alloc(0))
+})
+
 function tmpdir () {
   return path.join(os.tmpdir(), 'corestore-' + Math.random().toString(16).slice(2))
 }