fix: always catch and emit cache write errors in promise (#288)

lib/cache/entry.js

@@ -274,6 +274,8 @@ class CacheEntry {
       const cacheWritePromise = new Promise((resolve, reject) => {
         cacheWriteResolve = resolve
         cacheWriteReject = reject
+      }).catch((err) => {
+        body.emit('error', err)
       })
 
       body = new CachingMinipassPipeline({ events: ['integrity', 'size'] }, new MinipassFlush({

test/inaccessible-cache.js

@@ -0,0 +1,24 @@
+const nock = require('nock')
+const t = require('tap')
+const path = require('path')
+
+const fetch = require('../')
+nock.disableNetConnect()
+
+t.beforeEach(() => nock.cleanAll())
+t.test('catches error for inaccessible cache', async t => {
+  // a file for the cache which wont work
+  const cache = t.testdir({
+    file: '',
+  })
+  const req = nock('http://localhost')
+    .get('/foo')
+    .reply(() => [200, Buffer.from('text')])
+
+  const res = await fetch('http://localhost/foo', {
+    cachePath: path.resolve(cache, 'file'),
+  })
+
+  await t.rejects(res.text(), { code: 'ENOTDIR' })
+  t.ok(req.isDone())
+})