esbuild with proxy doesn't return Content-Language headers for OPTIONS request

[mivanyna]

Which @angular/* package(s) are the source of the bug?

upgrade, Don't known / other

Is this a regression?

Yes

Description

I upgraded my project to Angular 17 and switched to "builder": "@angular-devkit/build-angular:browser-esbuild". For local env I use proxy config to redirect requests to test env.

I receive all the data, except for OPTIONS request there is no Content-Language header in response.
It works on prev version(Angular 16 and "builder": "@angular-devkit/build-angular:browser")

Please provide a link to a minimal reproduction of the bug

No response

Please provide the exception or error you saw

No response

Please provide the environment you discovered this bug in (run ng version)

Angular CLI: 17.0.7
Node: 21.5.0 (Unsupported)
Package Manager: yarn 1.22.19
OS: win32 x64

Angular: 17.0.7
... animations, cli, common, compiler, compiler-cli, core, forms
... localize, platform-browser, platform-browser-dynamic, router
... upgrade

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1700.7
@angular-devkit/build-angular   17.0.7
@angular-devkit/architect       0.1700.7
@angular-devkit/build-angular   17.0.7
@angular-devkit/core            17.0.7
@angular-devkit/schematics      17.0.7
@schematics/angular             17.0.7
rxjs                            7.8.1
typescript                      5.2.2
zone.js                         0.14.2

Anything else?

I switched to "builder": "@angular-devkit/build-angular:browser-esbuild"
With proxy for the local env
package.json:

{
...
"start": "ng serve --proxy-config config/proxy.conf.js --hmr --port 3000 --open=true",
...
}

My proxy config looks like this:

const PROXY_CONFIG = [
  {
    context: [
      "/api"
    ],
    target: "test env link",
    secure: true,
    changeOrigin: true,
  }
]

module.exports = PROXY_CONFIG;

[mivanyna]

Please let me know if you need something from me

[mivanyna]

This one is very critical for me as it blocks development of some parts of the app

[alan-agius4]

Hi @mivanyna, to speed up our investigation kindly provide a minimal reproduction.

A good way to make a minimal repro is to create a new app via ng new repro-app and adding the minimum possible code to show the problem. Then you can push this repository to github and link it here.

That being said, it's unlikely this is a bug from our end as proxy is handled by Vite.

[alan-agius4]

@mivanyna, following an offline convo with @clydin, he correctly pointed out that an OPTIONS response has no content and thus, what is the reason of having a content-language header in the first place?

[mivanyna]

@alan-agius4 I get localizations in the header so I can then fetch the data with GET for the locale

[mivanyna]

Hi there, were you able to reproduce the issue?

[alan-agius4]

@mivanyna, unfortunately, I was not able yet to look into this issue. As mentioned above, it would definitely speed up the process if you share a minimal reproduction.

[ipranjic]

Hi @mivanyna, look at this issue: #25337
I think you have the same problem - the array form of proxy configuration is not yet supported by Vite. Instead you should do it like this:

module.exports = {
  "api/": { 
      target: "test env link",
      secure: true,
      changeOrigin: true
    }
 }

[mivanyna]

Hi @ipranjic , I don't think it's the case as I get all other data(GET, POST, etc)

[mivanyna]

@alan-agius4 here is the repo.

What I noticed is that even if the backend server is not running I get the response for OPTIONS request, seems like the dev-server returns it.