44d1a1cb15
This PR is part of a larger effort to migrate error messages to MDX and use App Router: https://github.com/vercel/front/pull/23459
48 lines
1.9 KiB
Text
48 lines
1.9 KiB
Text
---
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title: Dynamic code evaluation is not available in Middlewares or Edge API Routes
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---
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## Why This Error Occurred
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`eval()`, `new Function()` or compiling WASM binaries dynamically is not allowed in Middlewares or Edge API Routes.
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Specifically, the following APIs are not supported:
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- `eval()`
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- `new Function()`
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- `WebAssembly.compile`
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- `WebAssembly.instantiate` with [a buffer parameter](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/instantiate#primary_overload_%E2%80%94_taking_wasm_binary_code)
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## Possible Ways to Fix It
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You can bundle your WASM binaries using `import`:
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```ts filename="middleware.ts"
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import { NextResponse } from 'next/server'
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import squareWasm from './square.wasm?module'
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export default async function middleware() {
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const m = await WebAssembly.instantiate(squareWasm)
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const answer = m.exports.square(9)
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const response = NextResponse.next()
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response.headers.set('x-square', answer.toString())
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return response
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}
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```
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In rare cases, your code could contain (or import) some dynamic code evaluation statements which _can not be reached at runtime_ and which can not be removed by tree-shaking.
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You can relax the check to allow specific files with your Middleware or Edge API Route exported [configuration](/docs/pages/api-reference/edge#unsupported-apis):
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```tsx filename="pages/api/example.ts"
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export const config = {
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runtime: 'edge', // for Edge API Routes only
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unstable_allowDynamic: [
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'/lib/utilities.js', // allows a single file
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'/node_modules/function-bind/**', // use a glob to allow anything in the function-bind 3rd party module
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],
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}
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```
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`unstable_allowDynamic` is a glob, or an array of globs, ignoring dynamic code evaluation for specific files. The globs are relative to your application root folder.
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Be warned that if these statements are executed on the Edge, _they will throw and cause a runtime error_.
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