Previously you would be able to override only the QEMU package to be
used in the test runner. Frankly that doesn't help a lot if you are
trying to get a graphical session. The graphical session requires the
option in the NixOS module system to bet set to the correct QEMU
package.
In this commit I moved most of the test node configuration and
transformations into the `mkDriver` function (previously called
`driver`). The motivation was to be able to create a `driver` instance
with a given QEMU package that will be used consistently througout the
test expression.
According to Python documentation [0], `bufsize=1` is only meaningful in
text mode. As we don't pass in an argument called `universal_newlines`,
`encoding`, `errors` or `text` the file objects aren't opened in text
mode, which means the argument is ignored with a warning in Python 3.8.
line buffering (buffering=1) isn't supported in binary mode,
the default buffer size will be used
This commit removes this warning that appared when using
interactive test driver built with `-A driver`. This is done by
removing `bufsize=1` from Popen calls.
The default parameter when unspecified for `bufsize` is `-1` which
according to the documentation will be interpreted as
`io.DEFAULT_BUFFER_SIZE`. As mentioned by a warning, Python already
uses default buffer size when providing `buffering=1` parameter for
file objects not opened in text mode.
[0]: https://docs.python.org/3/library/subprocess.html#subprocess.Popen
This fixes an eval error that occurred on hydra with the small channel
and the `nixos.tests.boot.biosCdrom.x86_64-linux` attribute:
> $ nix-instantiate nixos/release-small.nix -A nixos.tests.boot.biosCdrom.x86_64-linux
> warning: unknown setting 'experimental-features'
> error: The option `virtualisation.qemu' does not exist. Definition values:
> - In `/home/andi/dev/nixos/nixpkgs/nixos/modules/testing/test-instrumentation.nix':
> {
> consoles = [ ];
> package = {
> _type = "override";
> content = <derivation /nix/store/q72h2cdcb9zjgiay5gdgzwddjkbjr7xq-qemu-host-cpu-only-for-vm-tests-5.1.0.drv>;
> ...
> (use '--show-trace' to show detailed location information)
In bc2188b we changed test test-instrumentation to also set the QEMU
package that is being used. That change unfortunately caused us to
always assing values to the virtualisation.qemu.package option even when
the option is not defined. The original code was explicitly testing for
the consoles case but the then newly extended version did not adjust the
check as the intention was probably not clear.
With this commit we are always ensuring the entire virtualisation.qemu
section exists and can thus drop the individual tests for each of the
sections since the QEMU module always defines both the package and the
consoles option when it's root is defined..
