lix/src/libexpr/primops/flake.cc

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#include "flake.hh"
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#include "primops.hh"
#include "eval-inline.hh"
#include "fetchGit.hh"
#include "download.hh"
#include "args.hh"
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#include <iostream>
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#include <queue>
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#include <regex>
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#include <nlohmann/json.hpp>
namespace nix {
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/* Read the registry or a lock file. (Currently they have an identical
format. */
static std::unique_ptr<FlakeRegistry> readRegistry(const Path & path)
{
auto registry = std::make_unique<FlakeRegistry>();
auto json = nlohmann::json::parse(readFile(path));
auto version = json.value("version", 0);
if (version != 1)
throw Error("flake registry '%s' has unsupported version %d", path, version);
auto flakes = json["flakes"];
for (auto i = flakes.begin(); i != flakes.end(); ++i) {
FlakeRegistry::Entry entry{FlakeRef(i->value("uri", ""))};
registry->entries.emplace(i.key(), entry);
}
return registry;
}
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/* Write the registry or lock file to a file. */
void writeRegistry(FlakeRegistry registry, Path path)
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{
nlohmann::json json = {};
json["version"] = 1;
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json["flakes"] = {};
for (auto elem : registry.entries) {
json["flakes"][elem.first] = elem.second.ref.to_string();
}
writeFile(path, json.dump(4)); // The '4' is the number of spaces used in the indentation in the json file.
}
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const FlakeRegistry & EvalState::getFlakeRegistry()
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{
std::call_once(_flakeRegistryInit, [&]()
{
#if 0
auto registryUri = "file:///home/eelco/Dev/gists/nix-flakes/registry.json";
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auto registryFile = getDownloader()->download(DownloadRequest(registryUri));
#endif
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auto registryFile = settings.nixDataDir + "/nix/flake-registry.json";
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_flakeRegistry = readRegistry(registryFile);
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});
return *_flakeRegistry;
}
Value * makeFlakeRegistryValue(EvalState & state)
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{
auto v = state.allocValue();
auto registry = state.getFlakeRegistry();
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state.mkAttrs(*v, registry.entries.size());
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for (auto & entry : registry.entries) {
auto vEntry = state.allocAttr(*v, entry.first);
state.mkAttrs(*vEntry, 2);
mkString(*state.allocAttr(*vEntry, state.symbols.create("uri")), entry.second.ref.to_string());
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vEntry->attrs->sort();
}
v->attrs->sort();
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return v;
}
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static FlakeRef lookupFlake(EvalState & state, const FlakeRef & flakeRef,
std::vector<const FlakeRegistry *> registries)
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{
if (auto refData = std::get_if<FlakeRef::IsFlakeId>(&flakeRef.data)) {
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for (auto registry : registries) {
auto i = registry->entries.find(refData->id);
if (i != registry->entries.end()) {
auto newRef = FlakeRef(i->second.ref);
if (!newRef.isDirect())
throw Error("found indirect flake URI '%s' in the flake registry", i->second.ref.to_string());
return newRef;
}
}
throw Error("cannot find flake '%s' in the flake registry or in the flake lock file", refData->id);
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} else
return flakeRef;
}
struct FlakeSourceInfo
{
Path storePath;
std::optional<Hash> rev;
};
static FlakeSourceInfo fetchFlake(EvalState & state, const FlakeRef & flakeRef)
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{
FlakeRef directFlakeRef = FlakeRef(flakeRef);
if (!flakeRef.isDirect())
{
std::vector<const FlakeRegistry *> registries;
// 'pureEval' is a setting which cannot be changed in `nix flake`,
// but without flagging it off, we can't use any FlakeIds.
// if (!evalSettings.pureEval) {
registries.push_back(&state.getFlakeRegistry());
// }
directFlakeRef = lookupFlake(state, flakeRef, registries);
}
assert(directFlakeRef.isDirect());
// NOTE FROM NICK: I don't see why one wouldn't fetch FlakeId flakes..
if (auto refData = std::get_if<FlakeRef::IsGitHub>(&directFlakeRef.data)) {
// FIXME: require hash in pure mode.
// FIXME: use regular /archive URLs instead? api.github.com
// might have stricter rate limits.
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// FIXME: support passing auth tokens for private repos.
auto url = fmt("https://api.github.com/repos/%s/%s/tarball/%s",
refData->owner, refData->repo,
refData->rev
? refData->rev->to_string(Base16, false)
: refData->ref
? *refData->ref
: "master");
auto result = getDownloader()->downloadCached(state.store, url, true, "source",
Hash(), nullptr, refData->rev ? 1000000000 : settings.tarballTtl);
if (!result.etag)
throw Error("did not receive an ETag header from '%s'", url);
if (result.etag->size() != 42 || (*result.etag)[0] != '"' || (*result.etag)[41] != '"')
throw Error("ETag header '%s' from '%s' is not a Git revision", *result.etag, url);
FlakeSourceInfo info;
info.storePath = result.path;
info.rev = Hash(std::string(*result.etag, 1, result.etag->size() - 2), htSHA1);
return info;
}
else if (auto refData = std::get_if<FlakeRef::IsGit>(&directFlakeRef.data)) {
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auto gitInfo = exportGit(state.store, refData->uri, refData->ref,
refData->rev ? refData->rev->to_string(Base16, false) : "", "source");
FlakeSourceInfo info;
info.storePath = gitInfo.storePath;
info.rev = Hash(gitInfo.rev, htSHA1);
return info;
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}
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else abort();
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}
Flake getFlake(EvalState & state, const FlakeRef & flakeRef)
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{
auto sourceInfo = fetchFlake(state, flakeRef);
debug("got flake source '%s' with revision %s",
sourceInfo.storePath, sourceInfo.rev.value_or(Hash(htSHA1)).to_string(Base16, false));
auto flakePath = sourceInfo.storePath;
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state.store->assertStorePath(flakePath);
if (state.allowedPaths)
state.allowedPaths->insert(flakePath);
FlakeRef newFlakeRef(flakeRef);
if (std::get_if<FlakeRef::IsGitHub>(&newFlakeRef.data)) {
FlakeSourceInfo srcInfo = fetchFlake(state, newFlakeRef);
if (srcInfo.rev) {
std::string uri = flakeRef.to_string();
newFlakeRef = FlakeRef(uri + "/" + srcInfo.rev->to_string());
}
}
Flake flake(newFlakeRef);
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Value vInfo;
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state.evalFile(flakePath + "/flake.nix", vInfo); // FIXME: symlink attack
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state.forceAttrs(vInfo);
if (auto name = vInfo.attrs->get(state.sName))
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flake.id = state.forceStringNoCtx(*(**name).value, *(**name).pos);
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else
throw Error("flake lacks attribute 'name'");
if (auto description = vInfo.attrs->get(state.sDescription))
flake.description = state.forceStringNoCtx(*(**description).value, *(**description).pos);
if (auto requires = vInfo.attrs->get(state.symbols.create("requires"))) {
state.forceList(*(**requires).value, *(**requires).pos);
for (unsigned int n = 0; n < (**requires).value->listSize(); ++n)
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flake.requires.push_back(FlakeRef(state.forceStringNoCtx(
*(**requires).value->listElems()[n], *(**requires).pos)));
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}
if (auto provides = vInfo.attrs->get(state.symbols.create("provides"))) {
state.forceFunction(*(**provides).value, *(**provides).pos);
flake.vProvides = (**provides).value;
} else
throw Error("flake lacks attribute 'provides'");
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auto lockFile = flakePath + "/flake.lock"; // FIXME: symlink attack
if (pathExists(lockFile)) {
flake.lockFile = readRegistry(lockFile);
for (auto & entry : flake.lockFile->entries)
if (!entry.second.ref.isImmutable())
throw Error("flake lock file '%s' contains mutable entry '%s'",
lockFile, entry.second.ref.to_string());
}
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return flake;
}
/* Given a flake reference, recursively fetch it and its
dependencies.
FIXME: this should return a graph of flakes.
*/
static std::tuple<FlakeId, std::map<FlakeId, Flake>> resolveFlake(EvalState & state,
const FlakeRef & topRef, bool impureTopRef)
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{
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std::map<FlakeId, Flake> done;
std::queue<std::tuple<FlakeRef, bool>> todo;
std::optional<FlakeId> topFlakeId; /// FIXME: ambiguous
todo.push({topRef, true});
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std::vector<const FlakeRegistry *> registries;
FlakeRegistry localRegistry;
registries.push_back(&localRegistry);
if (!evalSettings.pureEval)
registries.push_back(&state.getFlakeRegistry());
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while (!todo.empty()) {
auto [flakeRef, toplevel] = todo.front();
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todo.pop();
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if (auto refData = std::get_if<FlakeRef::IsFlakeId>(&flakeRef.data)) {
if (done.count(refData->id)) continue; // optimization
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flakeRef = lookupFlake(state, flakeRef, registries);
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}
if (evalSettings.pureEval && !flakeRef.isImmutable() && (!toplevel || !impureTopRef))
throw Error("mutable flake '%s' is not allowed in pure mode; use --no-pure-eval to disable", flakeRef.to_string());
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auto flake = getFlake(state, flakeRef);
if (done.count(flake.id)) continue;
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if (toplevel) topFlakeId = flake.id;
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for (auto & require : flake.requires)
todo.push({require, false});
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if (flake.lockFile)
for (auto & entry : flake.lockFile->entries) {
if (localRegistry.entries.count(entry.first)) continue;
localRegistry.entries.emplace(entry.first, entry.second);
}
done.emplace(flake.id, std::move(flake));
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}
assert(topFlakeId);
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return {*topFlakeId, std::move(done)};
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}
FlakeRegistry updateLockFile(EvalState & evalState, FlakeRef & flakeRef)
{
FlakeRegistry newLockFile;
std::map<FlakeId, Flake> myDependencyMap = get<1>(resolveFlake(evalState, flakeRef, false));
// Nick assumed that "topRefPure" means that the Flake for flakeRef can be
// fetched purely.
for (auto const& require : myDependencyMap) {
FlakeRegistry::Entry entry = FlakeRegistry::Entry(require.second.ref);
// The FlakeRefs are immutable because they come out of the Flake objects,
// not from the requires.
newLockFile.entries.insert(std::pair<FlakeId, FlakeRegistry::Entry>(require.first, entry));
}
return newLockFile;
}
void updateLockFile(EvalState & state, std::string path)
{
// 'path' is the path to the local flake repo.
FlakeRef flakeRef = FlakeRef(path);
if (std::get_if<FlakeRef::IsGit>(&flakeRef.data)) {
FlakeRegistry newLockFile = updateLockFile(state, flakeRef);
writeRegistry(newLockFile, path + "/flake.lock");
} else if (std::get_if<FlakeRef::IsGitHub>(&flakeRef.data)) {
throw UsageError("You can only update local flakes, not flakes on GitHub.");
} else {
throw UsageError("You can only update local flakes, not flakes through their FlakeId.");
}
}
Value * makeFlakeValue(EvalState & state, std::string flakeUri, Value & v)
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{
// FIXME: temporary hack to make the default installation source
// work.
bool impure = false;
if (hasPrefix(flakeUri, "impure:")) {
flakeUri = std::string(flakeUri, 7);
impure = true;
}
auto flakeRef = FlakeRef(flakeUri);
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auto [topFlakeId, flakes] = resolveFlake(state, flakeUri, impure);
// FIXME: we should call each flake with only its dependencies
// (rather than the closure of the top-level flake).
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auto vResult = state.allocValue();
state.mkAttrs(*vResult, flakes.size());
Value * vTop = 0;
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for (auto & flake : flakes) {
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auto vFlake = state.allocAttr(*vResult, flake.second.id);
if (topFlakeId == flake.second.id) vTop = vFlake;
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state.mkAttrs(*vFlake, 2);
mkString(*state.allocAttr(*vFlake, state.sDescription), flake.second.description);
auto vProvides = state.allocAttr(*vFlake, state.symbols.create("provides"));
mkApp(*vProvides, *flake.second.vProvides, *vResult);
vFlake->attrs->sort();
}
vResult->attrs->sort();
v = *vResult;
assert(vTop);
return vTop;
}
static void prim_getFlake(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
makeFlakeValue(state, state.forceStringNoCtx(*args[0], pos), v);
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}
static RegisterPrimOp r2("getFlake", 1, prim_getFlake);
}