[BUG] Error: Cannot set headers after they are sent to the client

[pflannery]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

Error Message

Error: Cannot set headers after they are sent to the client
	at new NodeError (node:internal/errors:405:5)
	at ClientRequest.setHeader (node:_http_outgoing:648:11)
	at Agent.addRequest (c:\Users\xxx\.vscode\extensions\pflannery.vscode-versionlens-1.11.0\node_modules\@npmcli\agent\lib\agents.js:178:13)
	at c:\Program Files\Microsoft VS Code\resources\app\node_modules.asar\agent-base\dist\index.js:77:31

A couple of users of my vscode extension versionlens have recently experienced this issue

Versionlens uses [email protected]. I tracked down this error to be related to a sub dependency of this package @npmcli/agent v2.2.2 which got installed in a recent update via the versionlens package-lock.json file.

The error occurs here

When the users rolled back versionlens they reported the error had gone away but the version they rolled back to also uses [email protected] so its a sub dependency update that is causing the problem.

I'm not sure how to recreate the issue as I can't seem to hit the line of code with the error so it seems to be npm config specific.

I'm wondering if the solution is as simple as adding a check

if (!request.headers.has('connection')) {
    request.headers.set('connection', agent ? 'keep-alive' : 'close')
  }

Expected Behavior

No errors

Steps To Reproduce

No response

Environment

• npm: 10.2.4
• Node: v18.19.1
• OS: Windows_NT x64 10.0.19045