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#include "primops.hh"
#include "store-api.hh"
#include "make-content-addressed.hh"
#include "url.hh"
namespace nix {
/**
* Handler for the content addressed case.
*
* @param state The evaluator state and store to write to.
* @param fromStore The store containing the path to rewrite.
* @param fromPath The source path to be rewritten.
* @param toPathMaybe The path to write the rewritten path to. If empty, the error shows the actual path.
* @param v The return `Value`
*/
static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, const std::optional<StorePath> & toPathMaybe, Value &v) {
// establish toPath or throw
if (!toPathMaybe || !state.store->isValidPath(*toPathMaybe)) {
auto rewrittenPath = makeContentAddressed(fromStore, *state.store, fromPath);
if (toPathMaybe && *toPathMaybe != rewrittenPath)
throw Error({
.msg = hintfmt("rewriting '%s' to content-addressed form yielded '%s', while '%s' was expected",
state.store->printStorePath(fromPath),
state.store->printStorePath(rewrittenPath),
state.store->printStorePath(*toPathMaybe)),
.errPos = state.positions[pos]
});
if (!toPathMaybe)
throw Error({
.msg = hintfmt(
"rewriting '%s' to content-addressed form yielded '%s'; "
"please set this in the 'toPath' attribute passed to 'fetchClosure'",
state.store->printStorePath(fromPath),
state.store->printStorePath(rewrittenPath)),
.errPos = state.positions[pos]
});
}
auto toPath = *toPathMaybe;
// check and return
auto resultInfo = state.store->queryPathInfo(toPath);
if (!resultInfo->isContentAddressed(*state.store)) {
// We don't perform the rewriting when outPath already exists, as an optimisation.
// However, we can quickly detect a mistake if the toPath is input addressed.
throw Error({
.msg = hintfmt("The 'toPath' value '%s' is input addressed, so it can't possibly be the result of rewriting. You may set 'toPath' to an empty string to figure out the correct path.",
state.store->printStorePath(toPath)),
.errPos = state.positions[pos]
});
}
state.mkStorePathString(toPath, v);
}
/**
* Fetch the closure and make sure it's content addressed.
*/
static void runFetchClosureWithContentAddressedPath(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, Value & v) {
if (!state.store->isValidPath(fromPath))
copyClosure(fromStore, *state.store, RealisedPath::Set { fromPath });
auto info = state.store->queryPathInfo(fromPath);
if (!info->isContentAddressed(*state.store)) {
throw Error({
.msg = hintfmt("The 'fromPath' value '%s' is input addressed, but input addressing was not requested. If you do intend to return an input addressed store path, add 'inputAddressed = true;' to the 'fetchClosure' arguments. Note that content addressing does not require users to configure a trusted binary cache public key on their systems, and is therefore preferred.",
state.store->printStorePath(fromPath)),
.errPos = state.positions[pos]
});
}
state.mkStorePathString(fromPath, v);
}
/**
* Fetch the closure and make sure it's input addressed.
*/
static void runFetchClosureWithInputAddressedPath(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, Value & v) {
if (!state.store->isValidPath(fromPath))
copyClosure(fromStore, *state.store, RealisedPath::Set { fromPath });
auto info = state.store->queryPathInfo(fromPath);
if (info->isContentAddressed(*state.store)) {
throw Error({
.msg = hintfmt("The 'fetchClosure' result, '%s' is not input addressed, despite 'inputAddressed' being set to true. It is preferable to return a content addressed path, so remove the 'inputAddressed' attribute to ensure content addressing is used in the future",
state.store->printStorePath(fromPath)),
.errPos = state.positions[pos]
});
}
state.mkStorePathString(fromPath, v);
}
static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
state.forceAttrs(*args[0], pos, "while evaluating the argument passed to builtins.fetchClosure");
std::optional<std::string> fromStoreUrl;
std::optional<StorePath> fromPath;
bool enableRewriting = false;
std::optional<StorePath> toPath;
std::optional<bool> inputAddressedMaybe;
for (auto & attr : *args[0]->attrs) {
const auto & attrName = state.symbols[attr.name];
auto attrHint = [&]() -> std::string {
return "while evaluating the '" + attrName + "' attribute passed to builtins.fetchClosure";
};
if (attrName == "fromPath") {
NixStringContext context;
fromPath = state.coerceToStorePath(attr.pos, *attr.value, context, attrHint());
}
else if (attrName == "toPath") {
state.forceValue(*attr.value, attr.pos);
enableRewriting = true;
if (attr.value->type() != nString || attr.value->string.s != std::string("")) {
NixStringContext context;
toPath = state.coerceToStorePath(attr.pos, *attr.value, context, attrHint());
}
}
else if (attrName == "fromStore")
fromStoreUrl = state.forceStringNoCtx(*attr.value, attr.pos,
attrHint());
else if (attrName == "inputAddressed")
inputAddressedMaybe = state.forceBool(*attr.value, attr.pos, attrHint());
else
throw Error({
.msg = hintfmt("attribute '%s' isn't supported in call to 'fetchClosure'", attrName),
.errPos = state.positions[pos]
});
}
if (!fromPath)
throw Error({
.msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromPath"),
.errPos = state.positions[pos]
});
bool inputAddressed = inputAddressedMaybe.value_or(false);
if (inputAddressed) {
if (toPath)
throw Error({
.msg = hintfmt("attribute '%s' is set to true, but '%s' is also set. Please remove one of them",
"inputAddressed",
"toPath"),
.errPos = state.positions[pos]
});
assert(!enableRewriting);
}
if (!fromStoreUrl)
throw Error({
.msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromStore"),
.errPos = state.positions[pos]
});
auto parsedURL = parseURL(*fromStoreUrl);
if (parsedURL.scheme != "http" &&
parsedURL.scheme != "https" &&
!(getEnv("_NIX_IN_TEST").has_value() && parsedURL.scheme == "file"))
throw Error({
.msg = hintfmt("'fetchClosure' only supports http:// and https:// stores"),
.errPos = state.positions[pos]
});
if (!parsedURL.query.empty())
throw Error({
.msg = hintfmt("'fetchClosure' does not support URL query parameters (in '%s')", *fromStoreUrl),
.errPos = state.positions[pos]
});
auto fromStore = openStore(parsedURL.to_string());
if (enableRewriting)
runFetchClosureWithRewrite(state, pos, *fromStore, *fromPath, toPath, v);
else if (inputAddressed)
runFetchClosureWithInputAddressedPath(state, pos, *fromStore, *fromPath, v);
else
runFetchClosureWithContentAddressedPath(state, pos, *fromStore, *fromPath, v);
}
static RegisterPrimOp primop_fetchClosure({
.name = "__fetchClosure",
.args = {"args"},
.doc = R"(
Fetch a Nix store closure from a binary cache, rewriting it into
content-addressed form. For example,
```nix
builtins.fetchClosure {
fromStore = "https://cache.nixos.org";
fromPath = /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1;
toPath = /nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1;
}
```
fetches `/nix/store/r2jd...` from the specified binary cache,
and rewrites it into the content-addressed store path
`/nix/store/ldbh...`.
If `fromPath` is already content-addressed, or if you are
allowing input addressing (`inputAddressed = true;`), then `toPath` may be
omitted.
To find out the correct value for `toPath` given a `fromPath`,
you can use `nix store make-content-addressed`:
```console
# nix store make-content-addressed --from https://cache.nixos.org /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1
rewrote '/nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1' to '/nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1'
```
This function is similar to `builtins.storePath` in that it
allows you to use a previously built store path in a Nix
expression. However, it is more reproducible because it requires
specifying a binary cache from which the path can be fetched.
Also, the default requirement of a content-addressed final store path
avoids the need for users to configure [`trusted-public-keys`](@docroot@/command-ref/conf-file.md#conf-trusted-public-keys).
This function is only available if you enable the experimental
feature `fetch-closure`.
)",
.fun = prim_fetchClosure,
.experimentalFeature = Xp::FetchClosure,
});
}
|
