fix: restore missing Netlify global type in @netlify/functions (#434)

* chore: fix existing vitest type tests

These weren't asserting anything, and vitest type tests weren't enabled.

* build: add missing `skipLibCheck`

This is a tough one to explain. This was a latent issue due to a confluence of things:
- we don't explicitly do type checking in this repo
- instead we rely implicitly on the fact that we use tsup in part to build `.dts` files, which
  performs type checking
- but tsup type checking behaves slightly differently than just running `tsc` in various little
  ways, largely because it's scoped per entrypoint
- we weren't setting `skipLibCheck: true` in the `tsconfig.json`, which seemed reasonable as there
  were no errors inside `node_modules/`
- now when I went to set up vitest type tests, this started type checking some stuff under the hood,
  and this failed with type errors inside `node_modules/`, despite it using our `tsconfig.json`
- it turns out this is because the tsup type checking approach was not encountering these errors;
  you can confirm this by running `npx --package=typescript tsc --noEmit` in `packages/functions/`

So, TL;DR: we had a latent necessity for `skipLibCheck` obscured by our weird implicit type checking via `tsup --dts`.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: serhalp <1377702+serhalp@users.noreply.github.com>
Co-authored-by: Philippe Serhal <philippe.serhal@netlify.com>

Author: Copilot

eslint.config.js

@@ -115,6 +115,9 @@ export default tseslint.config(
 
             // Custom assertion functions
             'assertNetlifyToml',
+
+            // Vitest type testing functions
+            'expectTypeOf',
           ],
         },
       ],

packages/functions/src/global-types.test.ts

@@ -0,0 +1,13 @@
+import { describe, test, expectTypeOf } from 'vitest'
+import type { NetlifyGlobal } from '@netlify/types'
+
+// Import the main module to ensure global augmentation is loaded
+import './main.js'
+
+describe('Netlify global type declaration regression test', () => {
+  test('should augment global scope with `Netlify` global', () => {
+    expectTypeOf<typeof Netlify>().toEqualTypeOf<NetlifyGlobal>()
+    expectTypeOf<typeof Netlify>().toHaveProperty('env')
+    expectTypeOf<typeof Netlify>().toHaveProperty('context')
+  })
+})

packages/functions/src/main.ts

@@ -1,3 +1,9 @@
+import type { NetlifyGlobal } from '@netlify/types'
+
+declare global {
+  const Netlify: NetlifyGlobal
+}
+
 export { builder } from './lib/builder.js'
 export { purgeCache } from './lib/purge_cache.js'
 export { schedule } from './lib/schedule.js'

packages/functions/tsconfig.json

@@ -11,6 +11,7 @@
     "removeComments": false,
     "strict": true,
     "moduleResolution": "node",
+    "skipLibCheck": true,
     "forceConsistentCasingInFileNames": true
   },
   "include": ["src", "dev"]

packages/functions/vitest.config.ts

@@ -7,5 +7,8 @@ export default defineConfig({
   test: {
     include: ['(src|dev)/**/*.test.ts'],
     testTimeout: 30_000,
+    typecheck: {
+      enabled: true,
+    },
   },
 })

packages/types/src/main.test.ts

@@ -4,12 +4,12 @@ import { fileURLToPath } from 'node:url'
 
 import { expect, expectTypeOf, test } from 'vitest'
 
-import { Context, NetlifyGlobal } from './main.js'
+import type { Context, NetlifyGlobal } from './main.js'
 import * as main from './main.js'
 
 test('Exports types', () => {
-  expectTypeOf<Context>()
-  expectTypeOf<NetlifyGlobal>()
+  expectTypeOf<Context>().toExtend<object>()
+  expectTypeOf<NetlifyGlobal>().toExtend<object>()
 })
 
 test('Does not export runtime code', () => {

packages/types/vitest.config.ts

@@ -0,0 +1,9 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    typecheck: {
+      enabled: true,
+    },
+  },
+})