We already have examples for these, but since we didn't actually
recognise the doubles, it wasn't possible to build any packages for
them without setting allowUnsupportedSystem.
Previously it would fail with
error: attribute 'nonexistent' missing
at nixpkgs/lib/filesystem.nix:29:10:
28| if dirOf path == path then "directory"
29| else (readDir (dirOf path)).${baseNameOf path};
| ^
30|
Previously this function couldn't handle / being passed, it would throw
an error:
error: attribute '' missing
at nixpkgs/lib/filesystem.nix:24:20:
23| */
24| pathType = path: (readDir (dirOf path)).${baseNameOf path};
| ^
25|
Consequently this also fixes the
lib.filesystem.{pathIsDirectory,pathIsRegularFile} functions.
Although Lens is based on a free core component ("OpenLens"), the tarballs
provided by Mirantis include a proprietary version of Lens that requires
a subscription.
As the proprietary option offers additional features, it would not be wise
to simply rewrite the derivation and base it on the FOSS source code.
Instead, implementing a new derivation for OpenLens is likely the better
approach.
I imagine this was supposed to be rustc = args.rustc, like the other
two lines. This meant that we accepted both rust and rustc
attributes, with the same effect. I doubt anybody was using the
undocumented, probably-accidental "rust" spelling, but we should
remove it before somebody starts.
In fact, we don't need to set rustc here at all, because no value
platforms.select could return will ever include a rustc key (unlike
the other two), so then rustc will be filled in later, when args is
merged into final.
This is to avoid stealing keys from submodules. `class` might be
common enough that reinterpreting existing `class` attributes in
configurations as a declaration leads to fairly widespread problems.
This is appears to be a fairly common mistake for beginners who want
to build larger things from the system configurations, such as NixOps
networks, etc. Further explanation seems appropriate.
The supposedly public nature of these functions has been holding
back module system maintenance, while usages of these functions
are expected to be rare. If used anywhere, presumably they're
emulating module system behavior because some use case isn't supported
properly. We should try to support such a use case directly, if it
even exists.
Some options have their default value set in the `config` instead of
`default`, for example to push `mkDefault`s down an attribute set.
In those cases, it's useful to provide a `defaultText` for informational
purposes.
