feat: support header matching in edge functions (#361)

* feat; support header matching in edge functions

* Update packages/edge-functions/dev/node/main.ts

Co-authored-by: Michal Piechowiak <misiek.piechowiak@gmail.com>

* refactor: simplify header check

---------

Co-authored-by: Michal Piechowiak <misiek.piechowiak@gmail.com>

Author: eduardoboucas

packages/edge-functions/dev/node/main.test.ts

@@ -196,6 +196,59 @@ describe('`EdgeFunctionsHandler`', () => {
     await fixture.destroy()
   })
 
+  test('Runs an edge function with header conditions', async () => {
+    const fixture = new Fixture()
+      .withFile(
+        'netlify.toml',
+        `[build]
+        publish = "public"
+        `,
+      )
+      .withFile(
+        'netlify/edge-functions/echo.mjs',
+        `export default async (req, context) => new Response("Hello from edge function");
+           
+         export const config = {
+           path: "/echo",
+           header: {
+             "x-present": true,
+             "x-absent": false,
+             "x-match": "something"
+           }
+         };`,
+      )
+
+    const directory = await fixture.create()
+    const handler = new EdgeFunctionsHandler({
+      configDeclarations: [],
+      directories: [path.resolve(directory, 'netlify/edge-functions')],
+      env: {},
+      geolocation,
+      logger: console,
+      siteID: '123',
+      siteName: 'test',
+    })
+
+    const req1 = new Request('https://site.netlify/echo')
+    req1.headers.set('x-nf-request-id', 'req-id')
+    expect(await handler.match(req1)).toBeFalsy()
+
+    const req2 = new Request('https://site.netlify/echo')
+    req2.headers.set('x-nf-request-id', 'req-id')
+    req2.headers.set('x-present', '1')
+    req2.headers.set('x-match', 'something good')
+    expect(await handler.match(req2)).toBeTruthy()
+
+    const req3 = new Request('https://site.netlify/echo')
+    req3.headers.set('x-nf-request-id', 'req-id')
+    req3.headers.set('x-present', '1')
+    req3.headers.set('x-absent', '1')
+    req3.headers.set('x-match', 'something good')
+    expect(await handler.match(req3)).toBeFalsy()
+
+    await fixture.destroy()
+  })
+
   test('Throws an error when the edge function has unparseable code', async () => {
     const fixture = new Fixture()
       .withFile(

packages/edge-functions/dev/node/main.ts

@@ -129,6 +129,32 @@ export class EdgeFunctionsHandler {
         return
       }
 
+      if (route.headers) {
+        const headerMatches = Object.entries(route.headers).every(([headerName, headerMatch]) => {
+          const requestHeaderValue = req.headers.get(headerName)
+
+          if (headerMatch?.matcher === 'exists') {
+            return requestHeaderValue !== null
+          }
+
+          if (headerMatch?.matcher === 'missing') {
+            return requestHeaderValue === null
+          }
+
+          if (requestHeaderValue && headerMatch?.matcher === 'regex') {
+            const pattern = new RegExp(headerMatch.pattern)
+
+            return pattern.test(requestHeaderValue.split(', ').join(','))
+          }
+
+          return false
+        })
+
+        if (!headerMatches) {
+          return
+        }
+      }
+
       const isExcludedForFunction = manifest.function_config[route.function]?.excluded_patterns?.some((pattern) =>
         new RegExp(pattern).test(url.pathname),
       )

packages/edge-functions/src/lib/config.ts

@@ -6,6 +6,8 @@ type OnError = 'fail' | 'bypass' | Path
 
 export type HTTPMethod = 'GET' | 'POST' | 'PUT' | 'PATCH' | 'DELETE' | 'OPTIONS'
 
+export type HeadersConfig = Record<string, boolean | string>
+
 type RateLimitAggregator = 'domain' | 'ip'
 
 type RateLimitAction = 'rate_limit' | 'rewrite'
@@ -29,6 +31,7 @@ export interface Config {
   cache?: Cache
   excludedPath?: Path | Path[]
   excludedPattern?: string | string[]
+  header?: HeadersConfig
   onError?: OnError
   path?: Path | Path[]
   pattern?: string | string[]