Throw if snapshots not opened

index.js

@@ -89,6 +89,10 @@ class BeeDiffStream extends Union {
       throw new Error('Incompatible Hypercore version--must have signedLength property')
     }
 
+    if (!leftSnapshot.opened || !rightSnapshot.opened) {
+      throw new Error('Snapshot must be opened')
+    }
+
     // We know that everything indexed in both snapshots is shared
     const sharedIndexedL = Math.min(
       leftSnapshot.core.signedLength, rightSnapshot.core.signedLength

test/basic.js

@@ -2,6 +2,8 @@ const test = require('brittle')
 const Hyperbee = require('hyperbee')
 const b4a = require('b4a')
 const Hypercore = require('hypercore')
+const tmpDir = require('test-tmp')
+const Corestore = require('corestore')
 
 const BeeDiffStream = require('../index')
 const { streamToArray, setup, encodedOpen, jsonKeyedOpen, confirm, replicateAndSync } = require('./helpers')
@@ -852,6 +854,34 @@ test('supports diffing values skipped by hyperbee encoding', async t => {
   t.alike(diffs.map(({ right }) => right?.key), [undefined, undefined]) // deletions
 })
 
+test('throws if a snapshot is not opened', async t => {
+  const store = new Corestore(await tmpDir())
+  const core = store.get({ name: 'bee' })
+  const bee = new Hyperbee(core)
+  t.exception(
+    () => new BeeDiffStream(bee, bee),
+    /Snapshot must be opened/,
+    'none open'
+  )
+
+  await bee.ready()
+  const snap = bee.snapshot()
+
+  t.exception(
+    () => new BeeDiffStream(bee, snap),
+    /Snapshot must be opened/,
+    'right not open'
+  )
+  t.exception(
+    () => new BeeDiffStream(snap, bee),
+    /Snapshot must be opened/,
+    'left not open'
+  )
+
+  await snap.ready()
+  t.execution(() => new BeeDiffStream(snap, bee), 'sanity check that happy path does not throw')
+})
+
 function sameKeysAndValues (t, actual, expected) {
   const extractKeysAndValues = ({ left, right }) => {
     const res = {}

test/complex.js

@@ -23,6 +23,7 @@ test('complex scenario with many diff cases', async t => {
 
   // Corresponds to the state just before going offline
   const baselineBee = base2.view.bee.snapshot()
+  await baselineBee.ready()
 
   t.is(base2.view.bee.core.signedLength, 13) // Sanity check
 
@@ -53,8 +54,10 @@ test('complex scenario with many diff cases', async t => {
   // State just before reconnecting with base1
   const refBee = base2.view.bee.snapshot()
 
+  const refBeeSnap = refBee.snapshot()
+  await refBeeSnap.ready()
   const [refNewState, refOldState] = diffsToValues(
-    await streamToArray(new BeeDiffStream(baselineBee, refBee.snapshot()))
+    await streamToArray(new BeeDiffStream(baselineBee, refBeeSnap))
   )
   t.alike(refNewState, [
     '2-1 added by 2',
@@ -106,6 +109,7 @@ test('complex scenario with many diff cases', async t => {
   // The peers sync and the autobases are linearised
   await confirm([base1, base2])
   const newBee = base2.view.bee.snapshot()
+  await newBee.ready()
   const [newState, refState] = diffsToValues(
     await streamToArray(new BeeDiffStream(refBee, newBee))
   )