Closes#193336Closes#261694
Related to #108984
The goal here was to get the following flake to build and run on
`aarch64-darwin`:
```nix
{ inputs.nixpkgs.url = <this branch>;
outputs = { nixpkgs, ... }: {
checks.aarch64-darwin.default =
nixpkgs.legacyPackages.aarch64-darwin.nixosTest {
name = "test";
nodes.machine = { };
testScript = "";
};
};
}
```
… and after this change it does. There's no longer a need for the
user to set `nodes.*.nixpkgs.pkgs` or
`nodes.*.virtualisation.host.pkgs` as the correct values are inferred
from the host system.
Aliases exist for a reason. Sure it is nice to make sure that
some aliases aren't used within Nixpkgs, but this creates two problems
which are far worse than your failing to meet your neatness compulsions.
- Users encounter missing attributes, https://github.com/NixOS/nixpkgs/issues/264577
wasting their time, stalling their progress, and even occupying others
time that would be better spent on fixing *real* issues.
- Hydra doesn't treat evaluation errors seriously enough, with the
effect that actual relevant test failures are masked by evaluation
failures such as those caused by this no aliases business.
- We don't even have the infrastructure to get rid of aliases, because
all warnings in package attributes are disallowed by Nixpkgs CI
tooling, last I checked.
Before re-disabling this, make sure that
- An actually helpful deprecation process is in place.
- Aliases are still allowed when `nixos-lib.runTests` and
`pkgs.testers.runNixOSTest` are invoked by external projects.
For instance, `all-tests.nix` could provide such an
override (e.g. with `newScope`).
When lib overrides were used, before this commit, they would not be made
available in the configuration evaluation of nixosTest's nodes.
Sample code:
``` nix
let
pkgs = import ./. {
overlays = [
(new: old: {
lib = old.lib.extend (self: super: {
sorry_dave = builtins.trace "There are no pod bay doors" "sorry dave";
});
})
];
};
in
pkgs.testers.nixosTest {
name = "demo lib overlay";
nodes = {
machine = { lib, ... }: {
environment.etc."got-lib-overlay".text = lib.sorry_dave;
};
};
testScript = { nodes }:
''
start_all()
machine.succeed('grep dave /etc/got-lib-overlay')
'';
}
```
By adding this option indirection, a test can declare all by itself
that it needs a custom nixpkgs. This is a more convenient way of
going about this when the caller of the test framework receives a
`node.pkgs` unconditionally.
Provide a window during which both solutions are valid without
warnings, in order to fight warning fatigue, and not to push 3rd
party repo maintainers to add unnecessary compat code.
This is a decomposition of the testing-python.nix and build-vms.nix
files into modules.
By refactoring the glue, we accomplish the following:
- NixOS tests can now use `imports` and other module system features.
- Network-wide test setup can now be reusable; example:
- A setup with all VMs configured to use a DNS server
- Split long, slow tests into multiple tests that import a
common module that has most of the setup.
- Type checking for the test arguments
- (TBD) "generated" options reference docs
- Aspects that had to be wired through all the glue are now in their
own files.
- Chief example: interactive.nix.
- Also: network.nix
In rewriting this, I've generally stuck as close as possible to the
existing code; copying pieces of logic and rewiring them, without
changing the logic itself.
I've made two exceptions to this rule
- Introduction of `extraDriverArgs` instead of hardcoded
interactivity logic.
- Incorporation of https://github.com/NixOS/nixpkgs/pull/144110
in testScript.nix.
I might revert the latter and split it into a new commit.
