Composer TransportException of recipes

[Gokujo]

Symfony version(s) affected

5.3

Description

I am working behind a proxy through Nexus 'cause the local network is not allowed to access the internet.
My problem is that symfony/flex tries to access recipe file on github.

[Composer\Downloader\TransportException]
  The "https://api.github.com/repos/symfony/recipes-contrib/contents/index.json?ref=flex/main" file could not be downloaded: php_network_getaddresses: getaddrinfo failed: Der angegebene Host ist unbekannt.   
  failed to open stream: php_network_getaddresses: getaddrinfo failed: Der angegebene Host ist unbekannt.

How to reproduce

composer create-project symfony/website-skeleton web

Possible Solution

I had to change the const DEFAULT_ENDPOINT in /vendor/symfony/flex/src/Downloader.php to

    private const DEFAULT_ENDPOINTS = [
        'http://localhost:91/_assets/composer/symfony/index.json',
        'http://localhost:91/_assets/composer/symfony/contrib/index.json',
    ];

I had to download the files locally and than link them to localhost

Additional Context

No response

[spider4216]

I had similar issue with symfony 4.4.33 with PHP 7.2.35 when composer update

[Composer\Downloader\TransportException] The "https://github.com/repos/symfony/recipes-contrib/contents/index.json?ref=flex/main" file could not be downloaded (HTTP/2 404 )

But in my case my network always redirect (301) me from api github to another url (server's problem)

You can modify endpoints in composer.json to prevent editing flex file in vendor

But in case with composer "extra" and env "SYMFONY_ENDPOINT" defaults endpoints also using :( I didn't find any solution to skip default symfony endpoints except change constant "DEFAULT_ENDPOINTS" or map it temporary in /etc/hosts

[nicolas-grekas]

Don't you use github for downloading the ZIP of each package?

[Gokujo]

Don't you use github for downloading the ZIP of each package?

Nope, I used the official command

composer create-project symfony/website-skeleton my_project_name

I only changed the const in vendor dir

[nicolas-grekas]

How do you make composer work if it can't access the internet?
How did flex work before v1.17? Was it silently disabled for example? Another behavior?

[Gokujo]

How do you make composer work if it can't access the internet? How did flex work before v1.17? Was it silently disabled for example? Another behavior?

Like I said in the first post I am using the Nexus proxy, for me it's only one work around.

[nicolas-grekas]

In #809 (comment), I suggested making URls in index.json relative.
I think that's the way to go for more flexibility.
Closing meanwhile. Please send a PR if you have some time to work on it!

[nicolas-grekas]

Relative URLs implemented in #872