This was a problem when writing a fetcher that uses e.g. sha256 hashes
for revisions. This doesn't actually do anything new, but allows for
creating such fetchers in the future (perhaps when support for Git's
SHA256 object format gains more popularity).
This was caused by SubstitutionGoal not setting the errorMsg field in
its BuildResult. We now get a more descriptive message than in 2.7.0, e.g.
error: path '/nix/store/13mh...' is required, but there is no substituter that can build it
instead of the misleading (since there was no build)
error: build of '/nix/store/13mh...' failed
Fixes#6295.
For each `nix.conf` option, add an empty html node with a unique `id`
that can be used as an anchor target. Also make the name of the option
be a link to that target so that it’s easily discoverable.
We can’t rewrite the whole list as an html definition list like it’s
done for the builtins because these options also appear in a man page,
and the manpage renderer (lowdown) can’t render arbitrary html. But the
hack here allows to keep the manpage and have the links in the html
version.
Fix https://github.com/NixOS/nix/issues/5745
Impure derivations are derivations that can produce a different result
every time they're built. Example:
stdenv.mkDerivation {
name = "impure";
__impure = true; # marks this derivation as impure
outputHashAlgo = "sha256";
outputHashMode = "recursive";
buildCommand = "date > $out";
};
Some important characteristics:
* This requires the 'impure-derivations' experimental feature.
* Impure derivations are not "cached". Thus, running "nix-build" on
the example above multiple times will cause a rebuild every time.
* They are implemented similar to CA derivations, i.e. the output is
moved to a content-addressed path in the store. The difference is
that we don't register a realisation in the Nix database.
* Pure derivations are not allowed to depend on impure derivations. In
the future fixed-output derivations will be allowed to depend on
impure derivations, thus forming an "impurity barrier" in the
dependency graph.
* When sandboxing is enabled, impure derivations can access the
network in the same way as fixed-output derivations. In relaxed
sandboxing mode, they can access the local filesystem.
The return value of BaseError::addTrace(...) is never used and
error-prone as subclasses calling it will return a BaseError instead of
the subclass.
This commit changes its return value to be void.
