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Lazily copy trees to the store

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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).
This commit is contained in:
Eelco Dolstra 2025-04-08 23:32:52 +02:00
parent c891554999
commit febd28db87
14 changed files with 122 additions and 50 deletions
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48
src/libflake/flake/flake.cc
View file

@ -84,37 +84,31 @@ static std::tuple<ref<SourceAccessor>, FlakeRef, FlakeRef> fetchOrSubstituteTree
return {fetched->accessor, resolvedRef, fetched->lockedRef};
}
static StorePath copyInputToStore(
EvalState & state,
fetchers::Input & input,
const fetchers::Input & originalInput,
ref<SourceAccessor> accessor)
{
auto storePath = fetchToStore(*state.store, accessor, FetchMode::Copy, input.getName());
state.allowPath(storePath); // FIXME: should just whitelist the entire virtual store
state.storeFS->mount(CanonPath(state.store->printStorePath(storePath)), accessor);
auto narHash = state.store->queryPathInfo(storePath)->narHash;
input.attrs.insert_or_assign("narHash", narHash.to_string(HashFormat::SRI, true));
assert(!originalInput.getNarHash() || storePath == originalInput.computeStorePath(*state.store));
return storePath;
}
static SourcePath maybeCopyInputToStore(
static StorePath mountInput(
EvalState & state,
fetchers::Input & input,
const fetchers::Input & originalInput,
ref<SourceAccessor> accessor,
CopyMode copyMode)
{
return copyMode == CopyMode::Lazy || (copyMode == CopyMode::RequireLockable && (input.isLocked() || input.getNarHash()))
? SourcePath(accessor)
: state.storePath(
copyInputToStore(state, input, originalInput, accessor));
auto storePath = StorePath::random(input.getName());
state.allowPath(storePath); // FIXME: should just whitelist the entire virtual store
state.storeFS->mount(CanonPath(state.store->printStorePath(storePath)), accessor);
if (copyMode == CopyMode::RequireLockable && !input.isLocked() && !input.getNarHash()) {
auto narHash = accessor->hashPath(CanonPath::root);
input.attrs.insert_or_assign("narHash", narHash.to_string(HashFormat::SRI, true));
}
// FIXME: check NAR hash
#if 0
assert(!originalInput.getNarHash() || storePath == originalInput.computeStorePath(*state.store));
#endif
return storePath;
}
static void forceTrivialValue(EvalState & state, Value & value, const PosIdx pos)
@ -440,7 +434,7 @@ static Flake getFlake(
// Re-parse flake.nix from the store.
return readFlake(
state, originalRef, resolvedRef, lockedRef,
maybeCopyInputToStore(state, lockedRef.input, originalRef.input, accessor, copyMode),
state.storePath(mountInput(state, lockedRef.input, originalRef.input, accessor, copyMode)),
lockRootAttrPath);
}
@ -805,7 +799,7 @@ LockedFlake lockFlake(
state, *input.ref, useRegistries, flakeCache);
return {
maybeCopyInputToStore(state, lockedRef.input, input.ref->input, accessor, inputCopyMode),
state.storePath(mountInput(state, lockedRef.input, input.ref->input, accessor, inputCopyMode)),
lockedRef
};
}