fix

If serve is set explicitly to false then root is required
If root is set, it must be validated

Author: Uzlopak

index.js

@@ -19,7 +19,7 @@ send.mime.default_type = 'application/octet-stream'
 
 /** @type {import("fastify").FastifyPluginAsync<import("./types").FastifyStaticOptions>} */
 async function fastifyStatic (fastify, opts) {
-  if (opts.serve !== false) {
+  if (opts.serve !== false || opts.root !== undefined) {
     opts.root = normalizeRoot(opts.root)
     checkRootPathForErrors(fastify, opts.root)
   }

test/static.test.js

@@ -1260,7 +1260,7 @@ test('maxAge option', async (t) => {
 })
 
 test('errors', async (t) => {
-  t.plan(11)
+  t.plan(12)
 
   await t.test('no root', async (t) => {
     t.plan(1)
@@ -1325,6 +1325,16 @@ test('errors', async (t) => {
     await t.assert.rejects(async () => await fastify.register(fastifyStatic, pluginOptions))
   })
 
+  await t.test('no root and serve: false', async (t) => {
+    t.plan(1)
+    const pluginOptions = {
+      serve: false,
+      root: []
+    }
+    const fastify = Fastify({ logger: false })
+    await t.assert.rejects(async () => await fastify.register(fastifyStatic, pluginOptions))
+  })
+
   await t.test('duplicate root paths are not allowed', async (t) => {
     t.plan(1)
     const pluginOptions = {