a3f0c63eed
We don't need to nest `cleanCargoSource` and `path` just to populate a default value for `name`. As they both ultimately delegate to `builtins.path`, the nesting can lead to IFD in situations which are otherwise avoidable
1.6 KiB
Source filtering
Nix considers that a derivation must be rebuilt whenever any of its inputs change, including all source files passed into the build. Unfortunately, this means that changes to any "irrelevant" files (such as the project README) would end up rebuilding the project even if the final outputs don't actually care about their contents!
Source filtering is a technique Nix employs that allows for better caching by programmatically filtering out files which are known to not apply to the build before the inputs are hashed.
A default source cleaner is available via craneLib.cleanCargoSource: it cleans
a source tree to omit things like version control directories as well omit any
non-Rust/non-cargo related files. It can be used like so:
craneLib.buildPackage {
# other attributes omitted
src = craneLib.cleanCargoSource ./.;
}
It is possible to customize the filter to use when cleaning the source by
leveraging craneLib.filterCargoSources. By default this filter will only keep
files whose names end with .rs or .toml. Though it is possible to compose it
with other filters, especially if it is necessary to include additional files
which it might otherwise omit:
let
# Only keeps markdown files
markdownFilter = path: _type: builtins.match ".*md$" path != null;
markdownOrCargo = path: type:
(markdownFilter path type) || (craneLib.filterCargoSources path type);
in
craneLib.buildPackage {
# other attributes omitted
src = lib.cleanSourceWith {
src = ./.; # The original, unfiltered source
filter = markdownOrCargo;
name = "source"; # Be reproducible, regardless of the directory name
};
}