fix NextApiRequestCookies and NextApiRequestQuery types

[mattbrandlysonos]

Hello! Thanks for making next.js so great.

Bug

Right now, these types give false confidence. These keys are treated as though a value is defined for every string. However, given an arbitrary request, a particular cookie or query param could be undefined.

For example, when building an /api endpoint, the code might look like this:

import type { NextApiRequest, NextApiResponse } from "next"

export default function handler(req: NextApiRequest, res: NextApiResponse) {
  // According to the old types, `value` is a string
  const value = req.cookies.value

  // Type-checking passes but leads to a runtime error when no `value` cookie is provided in the request
  //   Uncaught TypeError: Cannot read property 'toLowerCase' of undefined
  value.toLowerCause()

  // ...
}

By using Partial, TypeScript now knows that these objects don't have values defined for every key and accessing a given key might resolve to undefined.

---

The only obvious error this caused within this repo was on line 333 of the same file. For better or worse, I ended up casting that cookie value to a string. There's a series of if statements before it that, I guess, are guaranteeing that it's truly a string. Potentially, that stretch could be refactored such that TypeScript knows it's a string.

Also, I tried to follow the contributing guidelines. However, running yarn types kicked out a bunch of errors about overwriting files:

$ yarn types
yarn run v1.22.10
$ lerna run types --stream
lerna notice cli v4.0.0
lerna info Executing command in 2 packages: "yarn run types"
@next/env: $ tsc index.ts --declaration --emitDeclarationOnly --declarationDir types --esModuleInterop
next: $ tsc --declaration --emitDeclarationOnly --declarationDir dist
next: error TS5055: Cannot write file '/Users/mbrandly/code/next.js/packages/next/dist/build/index.d.ts' because it would overwrite input file.
next: error TS5055: Cannot write file '/Users/mbrandly/code/next.js/packages/next/dist/build/webpack/plugins/build-manifest-plugin.d.ts' because it would overwrite input file.
...
...
...

Let me know if there's anything I can improve here! Thanks again.

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
buildDuration	22.5s	22s	-494ms
buildDurationCached	8.7s	8.5s	-234ms
nodeModulesSize	479 MB	479 MB	⚠️ +71 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
/ failed reqs	0	0	✓
/ total time (seconds)	5.711	5.808	⚠️ +0.1
/ avg req/sec	437.79	430.45	⚠️ -7.34
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	2.173	2.197	⚠️ +0.02
/error-in-render avg req/sec	1150.55	1137.77	⚠️ -12.78

Client Bundles (main, webpack)

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
925.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42 kB	42 kB	✓
main-HASH.js gzip	29.2 kB	29.2 kB	✓
webpack-HASH.js gzip	1.54 kB	1.54 kB	✓
Overall change	72.9 kB	72.9 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
_app-HASH.js gzip	1.36 kB	1.36 kB	✓
_error-HASH.js gzip	193 B	193 B	✓
amp-HASH.js gzip	308 B	308 B	✓
css-HASH.js gzip	327 B	327 B	✓
dynamic-HASH.js gzip	2.71 kB	2.71 kB	✓
head-HASH.js gzip	359 B	359 B	✓
hooks-HASH.js gzip	920 B	920 B	✓
image-HASH.js gzip	5.73 kB	5.73 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.65 kB	2.65 kB	✓
routerDirect..HASH.js gzip	320 B	320 B	✓
script-HASH.js gzip	391 B	391 B	✓
withRouter-HASH.js gzip	318 B	318 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16 kB	16 kB	✓

Client Build Manifests

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
_buildManifest.js gzip	458 B	458 B	✓
Overall change	458 B	458 B	✓

Rendered Page Sizes

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
index.html gzip	533 B	533 B	✓
link.html gzip	547 B	547 B	✓
withRouter.html gzip	528 B	528 B	✓
Overall change	1.61 kB	1.61 kB	✓

---

Default Build with SWC

General Overall increase ⚠️

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
buildDuration	24.8s	25.1s	⚠️ +283ms
buildDurationCached	9s	8.4s	-639ms
nodeModulesSize	479 MB	479 MB	⚠️ +71 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
/ failed reqs	0	0	✓
/ total time (seconds)	5.703	5.83	⚠️ +0.13
/ avg req/sec	438.33	428.78	⚠️ -9.55
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	2.161	2.137	-0.02
/error-in-render avg req/sec	1156.77	1169.96	+13.19

Client Bundles (main, webpack)

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
925.HASH.js gzip	178 B	178 B	✓
framework-HASH.js gzip	42.7 kB	42.7 kB	✓
main-HASH.js gzip	29.6 kB	29.6 kB	✓
webpack-HASH.js gzip	1.54 kB	1.54 kB	✓
Overall change	74 kB	74 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	179 B	179 B	✓
amp-HASH.js gzip	311 B	311 B	✓
css-HASH.js gzip	324 B	324 B	✓
dynamic-HASH.js gzip	2.89 kB	2.89 kB	✓
head-HASH.js gzip	357 B	357 B	✓
hooks-HASH.js gzip	920 B	920 B	✓
image-HASH.js gzip	5.82 kB	5.82 kB	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	2.78 kB	2.78 kB	✓
routerDirect..HASH.js gzip	322 B	322 B	✓
script-HASH.js gzip	392 B	392 B	✓
withRouter-HASH.js gzip	317 B	317 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16.3 kB	16.3 kB	✓

Client Build Manifests

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
_buildManifest.js gzip	457 B	457 B	✓
Overall change	457 B	457 B	✓

Rendered Page Sizes

	vercel/next.js canary	mattbrandlysonos/next.js patch-1	Change
index.html gzip	532 B	532 B	✓
link.html gzip	547 B	547 B	✓
withRouter.html gzip	529 B	529 B	✓
Overall change	1.61 kB	1.61 kB	✓

Commit: 2fdf124

[ijjk]

Good catch, thanks for the PR!