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Detect cycles in flake follows.

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This change results in an error thrown as opposed to segfaulting due to
stack overflow.

Fixes #9144
This commit is contained in:
Vladimir Kryachko 2023-10-16 13:00:49 -04:00
parent 6bf68c1e64
commit b3fd7db63f
2 changed files with 50 additions and 4 deletions
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22
src/libexpr/flake/lockfile.cc
View file

@ -45,16 +45,26 @@ StorePath LockedNode::computeStorePath(Store & store) const
return lockedRef.input.computeStorePath(store);
}
std::shared_ptr<Node> LockFile::findInput(const InputPath & path)
{
static std::shared_ptr<Node> doFind(const ref<Node>& root, const InputPath & path, std::vector<std::string>& visited) {
auto pos = root;
auto pathS = printInputPath(path);
auto found = std::find(visited.cbegin(), visited.cend(), pathS);
if(found != visited.end()) {
std::vector cycle(found, visited.cend());
cycle.push_back(pathS);
throw Error("follow cycle detected: [%s]", concatStringsSep(" -> ", cycle));
}
visited.push_back(pathS);
for (auto & elem : path) {
if (auto i = get(pos->inputs, elem)) {
if (auto node = std::get_if<0>(&*i))
pos = *node;
else if (auto follows = std::get_if<1>(&*i)) {
if (auto p = findInput(*follows))
if (auto p = doFind(root, *follows, visited))
pos = ref(p);
else
return {};
@ -66,6 +76,12 @@ std::shared_ptr<Node> LockFile::findInput(const InputPath & path)
return pos;
}
std::shared_ptr<Node> LockFile::findInput(const InputPath & path)
{
std::vector<std::string> visited;
return doFind(root, path, visited);
}
LockFile::LockFile(const nlohmann::json & json, const Path & path)
{
auto version = json.value("version", 0);

30
tests/functional/flakes/follow-paths.sh
View file

@ -230,3 +230,33 @@ git -C "$flakeFollowsOverloadA" add flake.nix flakeB/flake.nix \
nix flake metadata "$flakeFollowsOverloadA"
nix flake update "$flakeFollowsOverloadA"
nix flake lock "$flakeFollowsOverloadA"
# Now test follow cycle detection
# We construct the following follows graph:
#
# foo
# / ^
# / \
# v \
# bar -> baz
# The message was
# error: follow cycle detected: [baz -> foo -> bar -> baz]
flakeFollowCycle="$TEST_ROOT/follows/followCycle"
# Test following path flakerefs.
mkdir -p "$flakeFollowCycle"
cat > $flakeFollowCycle/flake.nix <<EOF
{
description = "Flake A";
inputs = {
foo.follows = "bar";
bar.follows = "baz";
baz.follows = "foo";
};
outputs = { ... }: {};
}
EOF
checkRes=$(nix flake lock "$flakeFollowCycle" 2>&1 && fail "nix flake lock should have failed." || true)
echo $checkRes | grep -F "error: follow cycle detected: [baz -> foo -> bar -> baz]"