Lazy trees v2 #27
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Lazy trees v2 #27
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These don't need to evaluate anything (except for the flake metadata in flake.nix) so we can make these commands operate on lazy trees without risk of any semantic change in the evaluator. However, `nix flake metadata` now no longer prints the store path, which is a breaking change (but unavoidable if we want lazy trees).
For the top-level flake, we don't need a NAR hash. But for inputs, we do. Also, add a test for the lazy behaviour of `nix flake metadata|lock`.
We now mount lazy accessors on top of /nix/store without materializing them, and only materialize them to the real store if needed (e.g. in the `derivation` primop).
Something went wrong in NixOS#12068 so this didn't work. Also added a test.
Also, make fetchTree use InputCache.
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Motivation
Less invasive variant of NixOS#6530. We now mount lazy accessors on top of
/nix/storewithout materializing them, and only materialize them to the real store if needed (e.g. in thederivationprimop).The virtual store paths for the lazy accessors are currently random. This could be replaced by something more deterministic if desired.
Incorporates NixOS#12432.
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