From 956f442e29d23197d413b9ba5d2b952accae2e3f Mon Sep 17 00:00:00 2001
From: Daniel Roe <daniel@roe.dev>
Date: Mon, 26 Jul 2021 14:44:35 +0100
Subject: [PATCH] fix(nitro): filter out duplicate imports (#378)

---
 packages/nitro/src/rollup/plugins/middleware.ts | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/packages/nitro/src/rollup/plugins/middleware.ts b/packages/nitro/src/rollup/plugins/middleware.ts
index a2029dbeb8..9d000da6b2 100644
--- a/packages/nitro/src/rollup/plugins/middleware.ts
+++ b/packages/nitro/src/rollup/plugins/middleware.ts
@@ -6,6 +6,8 @@ import stdenv from 'std-env'
 import type { ServerMiddleware } from '../../server/middleware'
 import virtual from './virtual'
 
+const unique = (arr: any[]) => Array.from(new Set(arr))
+
 export function middleware (getMiddleware: () => ServerMiddleware[]) {
   const getImportId = p => '_' + hasha(p).substr(0, 6)
 
@@ -26,10 +28,16 @@ export function middleware (getMiddleware: () => ServerMiddleware[]) {
           }
         }
 
-        return `
-  ${middleware.filter(m => m.lazy === false).map(m => `import ${getImportId(m.handle)} from '${m.handle}';`).join('\n')}
+        // Imports take priority
+        const imports = unique(middleware.filter(m => m.lazy === false).map(m => m.handle))
 
-  ${middleware.filter(m => m.lazy !== false).map(m => `const ${getImportId(m.handle)} = () => import('${m.handle}');`).join('\n')}
+        // Lazy imports should fill in the gaps
+        const lazyImports = unique(middleware.filter(m => m.lazy !== false && !imports.includes(m.handle)).map(m => m.handle))
+
+        return `
+  ${imports.map(handle => `import ${getImportId(handle)} from '${handle}';`).join('\n')}
+
+  ${lazyImports.map(handle => `const ${getImportId(handle)} = () => import('${handle}');`).join('\n')}
 
   const middleware = [
     ${middleware.map(m => `{ route: '${m.route}', handle: ${getImportId(m.handle)}, lazy: ${m.lazy || true}, promisify: ${m.promisify !== undefined ? m.promisify : true} }`).join(',\n')}