How to read a symlink before using it with builtins.path?

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1

I’m passing src to a buildGoPackage derivation from builtins.path because I want to use a local source, but when I do I get back an error:

unpacking sources
unpacking source archive /nix/store/1v1382x47pd8aiky5waxdam6dazrb7w1-status-go-source-unknown
do not know how to unpack source archive /nix/store/1v1382x47pd8aiky5waxdam6dazrb7w1-status-go-source-unknown

But the source isn’t an archive, it’s a symlink to a folder:

 caspair > ls -l /nix/store/1v1382x47pd8aiky5waxdam6dazrb7w1-status-go-source-unknown
lrwxrwxrwx 1 root root 50 Jan  1  1970 /nix/store/1v1382x47pd8aiky5waxdam6dazrb7w1-status-go-source-unknown -> /home/sochan/go/src/github.com/status-im/status-go

What am I supposed to do? How can I do readlink for the path before I give it to builtins.path?

1 Like
2

I’m probably missing something but linking to files outside nix store is problematic, not least because it will cause builds not to work with sandbox enabled. Can’t you use src = /home/sochan/...;? It will copy to nix store every time the directory contents change but it should work.

Also, adding dontUnpack = true; to the derivation should skip the unpacking step but not sure it’s the right thing here. What do you want to achieve?

3

I’m using builtins.path because I also want to use the filter argument.
The issue is that the directory I’m pointing at is a symlink:
/home/sochan/work/status-go links to /home/sochan/go/src/github.com/status-im/status-go
Now, if I provide builtins.path with path set to /home/sochan/go/src/github.com/status-im/status-go(the real path) it works just fine, BUT if I use /home/sochan/work/status-go(the symlink) it fails with the do not know how to unpack source archive error because the Nix store entry becomes a symlink to /home/sochan/go/src/github.com/status-im/status-go.

My question is simple:
How can I use the symlink to the real directory and have Nix resolve it as the real path?

Something like:

src = builtins.path {
  path = lib.readlink "/home/sochan/work/status-go";
  filter = someFilter;
};
4

Thanks for clarification. I can’t offer any advice except perhaps changing the thread title to include nix store and symlinks?

There are couple related issues but none seems to hint at solution:

5

Override unpackPhase

6

You’re right, I updated the title. But I don’t really see a hit at the solution there.

Override unpackPhase

Seems ugly, also, the user is providing the path, so I don’t know when it’s a symlink and when it’s not. Having to add a custom unpackPhase every time a user can provide an src override for a build seems ugly. I guess if that’s the only way I’ll do it that way.

Though I do find it really weird that Nix doesn’t have something like builtins.readlink considering how often they are utilized in build environments.

Thanks for the suggestions.

7

Would that work if sandboxing is enabled? Can’t access /home in a sandboxed build…

8

How does that matter if I’m using builtins.path which creates an entry in /nix/store?

9

I was referring to @domenkozar’s suggestion of overriding unpackPhase. If builtins.path is copying a symlink pointing to /home, then builds won’t be able to read the files the symlink points to.

10

Ah, yes, you’re right.