From 4aea702ef0d11571b29ddb56babb478ff036e15b Mon Sep 17 00:00:00 2001
From: kaioduarte <duartedossantos@gmail.com>
Date: Wed, 10 Aug 2022 12:15:23 +0100
Subject: [PATCH 1/2] perf(swagger-module): lazy load swagger-ui-dist module

---
 lib/swagger-module.ts        |  3 ++-
 lib/swagger-ui/swagger-ui.ts | 16 +++++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/lib/swagger-module.ts b/lib/swagger-module.ts
index 5235d913a..68e86376d 100644
--- a/lib/swagger-module.ts
+++ b/lib/swagger-module.ts
@@ -12,7 +12,7 @@ import { SwaggerScanner } from './swagger-scanner';
 import {
   buildSwaggerHTML,
   buildSwaggerInitJS,
-  swaggerAssetsAbsoluteFSPath
+  getSwaggerAssetsAbsoluteFSPath
 } from './swagger-ui';
 import { assignTwoLevelsDeep } from './utils/assign-two-levels-deep';
 import { getGlobalPrefix } from './utils/get-global-prefix';
@@ -44,6 +44,7 @@ export class SwaggerModule {
 
   private static serveStatic(finalPath: string, app: INestApplication) {
     const httpAdapter = app.getHttpAdapter();
+    const swaggerAssetsAbsoluteFSPath = getSwaggerAssetsAbsoluteFSPath();
 
     if (httpAdapter && httpAdapter.getType() === 'fastify') {
       (app as NestFastifyApplication).useStaticAssets({
diff --git a/lib/swagger-ui/swagger-ui.ts b/lib/swagger-ui/swagger-ui.ts
index 4c21549b8..aa5e3e0d1 100644
--- a/lib/swagger-ui/swagger-ui.ts
+++ b/lib/swagger-ui/swagger-ui.ts
@@ -1,4 +1,3 @@
-import * as swaggerUi from 'swagger-ui-dist';
 import { favIconHtml, htmlTemplateString, jsTemplateString } from './constants';
 import { OpenAPIObject, SwaggerCustomOptions } from '../interfaces';
 import { buildJSInitOptions } from './helpers';
@@ -21,10 +20,21 @@ export function buildSwaggerInitJS(
   return jsTemplateString.replace('<% swaggerOptions %>', jsInitOptions);
 }
 
+let swaggerAssetsAbsoluteFSPath;
+
 /**
- * Stores absolute path to swagger-ui assets
+ * Returns the absolute path to swagger-ui assets.
  */
-export const swaggerAssetsAbsoluteFSPath = swaggerUi.getAbsoluteFSPath();
+export function getSwaggerAssetsAbsoluteFSPath() {
+  if (!swaggerAssetsAbsoluteFSPath) {
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
+    const swaggerUi = require('swagger-ui-dist');
+    swaggerAssetsAbsoluteFSPath = swaggerUi.getAbsoluteFSPath();
+  }
+
+  return swaggerAssetsAbsoluteFSPath;
+}
+
 /**
  * Used to build swagger-ui custom html
  */

From 857a2d8e85b56d19dd237c400843296aa8809217 Mon Sep 17 00:00:00 2001
From: kaioduarte <duartedossantos@gmail.com>
Date: Wed, 10 Aug 2022 13:14:18 +0100
Subject: [PATCH 2/2] chore: address code review comment

---
 lib/swagger-ui/swagger-ui.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/swagger-ui/swagger-ui.ts b/lib/swagger-ui/swagger-ui.ts
index aa5e3e0d1..812fdf4ba 100644
--- a/lib/swagger-ui/swagger-ui.ts
+++ b/lib/swagger-ui/swagger-ui.ts
@@ -20,7 +20,7 @@ export function buildSwaggerInitJS(
   return jsTemplateString.replace('<% swaggerOptions %>', jsInitOptions);
 }
 
-let swaggerAssetsAbsoluteFSPath;
+let swaggerAssetsAbsoluteFSPath: string | undefined;
 
 /**
  * Returns the absolute path to swagger-ui assets.