esm(network imports): expose User-Agent header

[Fyko]

What is the problem this feature will solve?

We're building a registry server to serve our JavaScript packages in a variety of runtimes -- Node.js, Deno and the browser. Both the browser and Deno include a User-Agent header, but Node doesn't.

What is the feature you are proposing to solve the problem?

I propose altering the GET functions to include the user-agent header.

node/lib/internal/modules/esm/fetch_module.js

Lines 47 to 69 in 5e3d003

	let HTTPSAgent;
	function HTTPSGet(url, opts) {
	const https = require('https'); // [1]
	HTTPSAgent ??= new https.Agent({ // [2]
	keepAlive: true,
	});
	return https.get(url, {
	agent: HTTPSAgent,
	...opts,
	});
	}
	let HTTPAgent;
	function HTTPGet(url, opts) {
	const http = require('http'); // [1]
	HTTPAgent ??= new http.Agent({ // [2]
	keepAlive: true,
	});
	return http.get(url, {
	agent: HTTPAgent,
	...opts,
	});
	}

However, this poses some security concerns. Should it be exposed by default? Should there be another flag?
node --experimental-network-imports --experimental-network-imports-expose-ua ./foo.mjs.

[JakobJingleheimer]

FYI we're considering replacing fetch_module with fetch

[bnoordhuis]

The ask is basically to add this?

diff --git a/lib/internal/modules/esm/fetch_module.js b/lib/internal/modules/esm/fetch_module.js
index d79e5a5eb99..7a52ae4c985 100644
--- a/lib/internal/modules/esm/fetch_module.js
+++ b/lib/internal/modules/esm/fetch_module.js
@@ -124,6 +124,7 @@ function fetchWithRedirects(parsed) {
   const result = (async () => {
     const req = handler(parsed, {
       headers: { Accept: '*/*' },
+      'User-Agent': 'node',
     });
     // Note that `once` is used here to handle `error` and that it hits the
     // `finally` on network error/timeout.

Pull request welcome, I think? Adding the version might leak a little too much info but then again, maybe not.

edit: I missed #43852 already exists and met some fierce opposition.

[renhiyama]

The ask is basically to add this?

diff --git a/lib/internal/modules/esm/fetch_module.js b/lib/internal/modules/esm/fetch_module.js
index d79e5a5eb99..7a52ae4c985 100644
--- a/lib/internal/modules/esm/fetch_module.js
+++ b/lib/internal/modules/esm/fetch_module.js
@@ -124,6 +124,7 @@ function fetchWithRedirects(parsed) {
   const result = (async () => {
     const req = handler(parsed, {
       headers: { Accept: '*/*' },
+      'User-Agent': 'node',
     });
     // Note that `once` is used here to handle `error` and that it hits the
     // `finally` on network error/timeout.

Pull request welcome, I think? Adding the version might leak a little too much info but then again, maybe not.

edit: I missed #43852 already exists and met some fierce opposition.

I would suggest something more informative + align with deno user agent: Node/{version}

It would help servers polyfill features if not supported on current version of nodejs, etc

[github-actions]

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[github-actions]

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For more information on how the project manages feature requests, please consult the feature request management document.