fix: Respect ignoreTrailingSlash.

Fixes #5

Author: ShogunPanda

src/ui.ts

@@ -7,6 +7,12 @@ import { resolve } from 'node:path'
 import { getAbsoluteFSPath } from 'swagger-ui-dist'
 
 export function addUI(instance: FastifyInstance, prefix: string): void {
+  let indexUrl = `${prefix}/`
+
+  if (instance.initialConfig.ignoreTrailingSlash) {
+    indexUrl += 'index.html'
+  }
+
   // Get the main index file and patch it
   const swaggerUIRoot = getAbsoluteFSPath()
   const swaggerUIInitializer = readFileSync(resolve(swaggerUIRoot, 'swagger-initializer.js'), 'utf8').replace(
@@ -19,7 +25,7 @@ export function addUI(instance: FastifyInstance, prefix: string): void {
     method: 'GET',
     url: prefix,
     handler(_: FastifyRequest, reply: FastifyReply): void {
-      reply.redirect(301, `${prefix}/`)
+      reply.redirect(301, indexUrl)
     }
   })
 

test/ui.test.ts

@@ -69,5 +69,49 @@ t.test('UI serving', t => {
     t.ok(initializerBodyV2.indexOf('url: "/v2/openapi.json",') > 0)
   })
 
+  t.test('should respect ignoreTrailingSlash option', async t => {
+    {
+      const server = fastify({ ignoreTrailingSlash: false })
+
+      await server.register(fastifyOpenApiDocs, {})
+
+      const initialRequest = await server.inject('/docs')
+
+      t.equal(initialRequest.statusCode, 301)
+      t.equal(initialRequest.body, '')
+      t.equal(initialRequest.headers.location, '/docs/')
+
+      const redirectedRequest = await server.inject('/docs/')
+      t.equal(redirectedRequest.statusCode, 200)
+    }
+
+    {
+      const server = fastify({ ignoreTrailingSlash: true })
+
+      await server.register(fastifyOpenApiDocs, {})
+
+      const initialRequest = await server.inject('/docs')
+
+      t.equal(initialRequest.statusCode, 301)
+      t.equal(initialRequest.body, '')
+      t.equal(initialRequest.headers.location, '/docs/index.html')
+    }
+
+    {
+      const server = fastify({ ignoreTrailingSlash: true })
+
+      await server.register(fastifyOpenApiDocs, {})
+
+      const initialRequest = await server.inject('/docs/')
+
+      t.equal(initialRequest.statusCode, 301)
+      t.equal(initialRequest.body, '')
+      t.equal(initialRequest.headers.location, '/docs/index.html')
+
+      const redirectedRequest = await server.inject('/docs/index.html')
+      t.equal(redirectedRequest.statusCode, 200)
+    }
+  })
+
   t.end()
 })