installing specific php extension version defaults to latest

[SirStone]

What happened?

I'm trying to install the package php81Extensions.mongodb@1.15
The install looks fine and a devbox update gives me
Info: Already up-to-date php81Extensions.mongodb@1.15 1.15.0

but if I run php -r "phpinfo(INFO_MODULES);" | grep -B 3 -i version |grep MongoDB i get

2.1.1 is the latest version

Steps to reproduce

1. devbox add php@8.1 install php 8.1
2. devbox add php81Extensions.mongodb@1.15 install the php extension
3. php -r "phpinfo(INFO_MODULES);" | grep -B 3 -i version |grep MongoDB check asking to PHP the version of the loaded extension

Command

No response

devbox.json

{
  "$schema": "https://raw.githubusercontent.com/jetify-com/devbox/0.14.2/.schema/devbox.schema.json",
  "packages": [
    "php@8.1",
    "php81Extensions.mongodb@1.15"
  ],
  "shell": {
    "init_hook": [
      "echo 'Welcome to devbox!' > /dev/null"
    ],
    "scripts": {
      "test": [
        "echo \"Error: no test specified\" && exit 1"
      ]
    }
  }
}

Devbox version

0.15.1

Nix version

nix (Determinate Nix 3.6.6) 2.29.0

What system does this bug occur on?

Linux (x86-64)

Debug logs

No response

[mikeland73]

Triage: looks hard, p3.

Resolution is correct. https://search.devbox.sh/v2/resolve?name=php81Extensions.mongodb&version=1.15 resolves to 1.15.0 at nixpkgs 842e9093.... That is why devbox update reports 1.15.0.

Root cause. The php plugin never loads that resolved package. Its flake (plugins/php/flake.nix:12-18) builds PHP with extensions like this:

(builtins.match "^php.*Extensions\.([^@]*).*$" "{{ . }}")   # keeps only the extension *name*
...
php = nixpkgs.legacyPackages.<system>.<php attr>.withExtensions ({ enabled, all }: enabled ++ map (ext: all.${ext}) extensions);

The @1.15 part is discarded, and the extension is taken from all.<ext> in the same nixpkgs revision as php@8.1. That revision has mongodb 2.1.1, which is what phpinfo() shows. The separately installed 1.15.0 derivation is never wired into PHP's extension= config.

Why it's hard. Honouring the version means pulling the extension from a different nixpkgs revision than PHP. PHP extensions are ABI-coupled to the exact PHP build, so a naive mix will often fail to load. A proper fix would need to either:

• rebuild the extension from the pinned revision's source against the current PHP (e.g. all.mongodb.overrideAttrs with the old src/version), or
• resolve PHP and the extension to a common nixpkgs revision.

Cheap improvement. Until then, the plugin could warn when a phpXXExtensions.* package carries a version other than latest, since that version is currently ignored.

Workaround. Pick a php@8.1.x version whose nixpkgs revision shipped mongodb 1.15, so both come from the same revision.

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