fix: expose getPublicKey (#1188)

This is used externally by IPFS so expose the method

test/core/get-public-key.spec.ts

@@ -0,0 +1,78 @@
+/* eslint-env mocha */
+
+import { expect } from 'aegir/chai'
+import { WebSockets } from '@libp2p/websockets'
+import { NOISE } from '@chainsafe/libp2p-noise'
+import { createPeerId } from '../utils/creators/peer.js'
+import { createLibp2pNode, Libp2pNode } from '../../src/libp2p.js'
+import type { Libp2pOptions } from '../../src/index.js'
+import sinon from 'sinon'
+import { KadDHT } from '@libp2p/kad-dht'
+
+describe('getPublicKey', () => {
+  let libp2p: Libp2pNode
+
+  beforeEach(async () => {
+    const peerId = await createPeerId()
+    const config: Libp2pOptions = {
+      peerId,
+      transports: [
+        new WebSockets()
+      ],
+      connectionEncryption: [
+        NOISE
+      ],
+      dht: new KadDHT()
+    }
+    libp2p = await createLibp2pNode(config)
+
+    await libp2p.start()
+  })
+
+  afterEach(async () => {
+    await libp2p.stop()
+  })
+
+  it('should extract embedded public key', async () => {
+    const otherPeer = await createPeerId()
+
+    const key = await libp2p.getPublicKey(otherPeer)
+
+    expect(otherPeer.publicKey).to.equalBytes(key)
+  })
+
+  it('should get key from the keystore', async () => {
+    const otherPeer = await createPeerId({ opts: { type: 'rsa' } })
+
+    if (otherPeer.publicKey == null) {
+      throw new Error('Public key was missing')
+    }
+
+    await libp2p.peerStore.keyBook.set(otherPeer, otherPeer.publicKey)
+
+    const key = await libp2p.getPublicKey(otherPeer)
+
+    expect(otherPeer.publicKey).to.equalBytes(key)
+  })
+
+  it('should query the DHT when the key is not in the keystore', async () => {
+    const otherPeer = await createPeerId({ opts: { type: 'rsa' } })
+
+    if (otherPeer.publicKey == null) {
+      throw new Error('Public key was missing')
+    }
+
+    if (libp2p.dht == null) {
+      throw new Error('DHT was not configured')
+    }
+
+    libp2p.dht.get = sinon.stub().returns([{
+      name: 'VALUE',
+      value: otherPeer.publicKey
+    }])
+
+    const key = await libp2p.getPublicKey(otherPeer)
+
+    expect(otherPeer.publicKey).to.equalBytes(key)
+  })
+})