This is a bit complex because we want to expose extra functionality the
wrapped class has. Perhaps there is some inheritancy trickery to do this
nicer, but I don't know it, and this is the first thing we tried after a
series of attempts that did build.
This design is kind of like that of Rust's Writer, Reader, or Iter
adapters, which impliment more traits based on what the inner type
implements.
This was introduced in fa125b9b28, and
then "reverted" in 1cf4801108, except that
revert left the struct around doing nothing useful.
We're removing it all the way now because we want to make a new
`TeeSink` complementing the already-exiting `TeeSource`, that is
actually a completely different concept as far as the class hierarchy is
concerned.
Not implementing anything here, just throwing an error if a derivation
sets `__contentAddressed = true` without
`--experimental-features content-addressed-paths`
(and also with it as there's nothing implemented yet)
On nix-env -qa -f '<nixpkgs>', this reduces maximum RSS by 20970 KiB
and runtime by 0.8%. This is mostly because we're not parsing the hash
part as a hash anymore (just validating that it consists of base-32
characters).
Also, replace storePathToHash() by StorePath::hashPart().
E.g. instead of
error: --- BuildError ----------------------------------------------- nix
builder for '/nix/store/03nk0a3n8h2948k4lqfgnnmym7knkcma-foo.drv' failed with exit code 1
error: --- Error ---------------------------------------------------- nix
build of '/nix/store/03nk0a3n8h2948k4lqfgnnmym7knkcma-foo.drv' failed
we now get
error: --- Error ---------------------------------------------------- nix
builder for '/nix/store/03nk0a3n8h2948k4lqfgnnmym7knkcma-foo.drv' failed with exit code 1
This function was used in only one place, where it could easily be
replaced by readDerivation() since it's not
performance-critical. (This function appears to have been modelled
after queryDerivationOutputs(), which exists only to make the garbage
collector faster.)
