[pavstev]

PR Checklist

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

The NodeAdapter sends a Content-Type as the app gives it. Express runs it through mime-types, so it adds ; charset=utf-8 to text/*, application/json and the other types that have a charset.

@Get()
@Header('Content-Type', 'text/html')
page() {
  return '<p>zażółć</p>';
}

adapter	Content-Type sent
express	text/html; charset=utf-8
node	text/html

A browser then guesses the charset, and non-ASCII text can show up broken. The same happens with res.set(), res.header() and res.type('text/html') on the node response. res.set('Content-Type', [...]) is accepted, but Express throws a TypeError.

Issue Number: N/A

What is the new behavior?

NodeResponse.set() (and so header(), and type()) and NodeAdapter.setHeader() (the @Header() path, as in the ExpressAdapter) run a Content-Type through the same mime-types lookup that type() already used:

adapter	Content-Type sent
express	text/html; charset=utf-8
node	text/html; charset=utf-8

• A value with a charset stays as it is: text/html; charset=latin1.
• A type with no charset in mime-db stays as it is: application/vnd.api+json, image/png.
• An unknown value stays as it is (the || value fallback), so it is never turned into false.
• An array as the Content-Type throws TypeError('Content-Type cannot be set to an Array'), as Express does.

Tests: node-request.spec.ts (set()/header() and type()), node-adapter.spec.ts (setHeader() then reply()), and a @Header('Content-Type', 'text/html') route in integration/http-adapters that runs for express and node. All new cases fail on master and pass with the fix. One old send() test expected text/html back for set('Content-Type', 'text/html'); it now expects the charset, as Express sends it.

Not in this PR: Express res.send(string) also adds the charset to a preset type that has none in mime-db (res.set('Content-Type', 'application/vnd.api+json').send('...') gives application/vnd.api+json; charset=utf-8). The node adapter keeps the type as it is. I left it out to keep this change small. I can send it as a follow-up if you want it.

Does this PR introduce a breaking change?

• Yes
• No

@nestjs/platform-node is new in 12.3. An app that sets text/html by hand now gets the charset, which is what Express sends too.

Other information

Found by comparing the NodeAdapter with Express 5.3 for the same @Header() route.