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Represent 'follows' inputs explicitly in the lock file

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This fixes an issue where lockfile generation was not idempotent:
after updating a lockfile, a "follows" node would end up pointing to a
new copy of the node, rather than to the original node.
This commit is contained in:
Eelco Dolstra 2020-06-11 14:40:21 +02:00
parent 195ed43b60
commit 0c62b4ad0f
8 changed files with 165 additions and 111 deletions
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77
src/libexpr/flake/lockfile.cc
View file

@ -41,15 +41,22 @@ StorePath LockedNode::computeStorePath(Store & store) const
return lockedRef.input.computeStorePath(store);
}
std::shared_ptr<Node> Node::findInput(const InputPath & path)
std::shared_ptr<Node> LockFile::findInput(const InputPath & path)
{
auto pos = shared_from_this();
auto pos = root;
if (!pos) return {};
for (auto & elem : path) {
auto i = pos->inputs.find(elem);
if (i == pos->inputs.end())
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)) {
pos = findInput(*follows);
if (!pos) return {};
}
} else
return {};
pos = i->second;
}
return pos;
@ -58,7 +65,7 @@ std::shared_ptr<Node> Node::findInput(const InputPath & path)
LockFile::LockFile(const nlohmann::json & json, const Path & path)
{
auto version = json.value("version", 0);
if (version < 5 || version > 6)
if (version < 5 || version > 7)
throw Error("lock file '%s' has unsupported version %d", path, version);
std::unordered_map<std::string, std::shared_ptr<Node>> nodeMap;
@ -69,21 +76,37 @@ LockFile::LockFile(const nlohmann::json & json, const Path & path)
{
if (jsonNode.find("inputs") == jsonNode.end()) return;
for (auto & i : jsonNode["inputs"].items()) {
std::string inputKey = i.value();
auto k = nodeMap.find(inputKey);
if (k == nodeMap.end()) {
auto jsonNode2 = json["nodes"][inputKey];
auto input = std::make_shared<LockedNode>(jsonNode2);
k = nodeMap.insert_or_assign(inputKey, input).first;
getInputs(*input, jsonNode2);
if (i.value().is_array()) {
InputPath path;
for (auto & j : i.value())
path.push_back(j);
node.inputs.insert_or_assign(i.key(), path);
} else {
std::string inputKey = i.value();
auto k = nodeMap.find(inputKey);
if (k == nodeMap.end()) {
auto jsonNode2 = json["nodes"][inputKey];
auto input = std::make_shared<LockedNode>(jsonNode2);
k = nodeMap.insert_or_assign(inputKey, input).first;
getInputs(*input, jsonNode2);
}
if (auto child = std::dynamic_pointer_cast<LockedNode>(k->second))
node.inputs.insert_or_assign(i.key(), child);
else
// FIXME: replace by follows node
throw Error("lock file contains cycle to root node");
}
node.inputs.insert_or_assign(i.key(), k->second);
}
};
std::string rootKey = json["root"];
nodeMap.insert_or_assign(rootKey, root);
getInputs(*root, json["nodes"][rootKey]);
// FIXME: check that there are no cycles in version >= 7. Cycles
// between inputs are only possible using 'follows' indirections.
// Once we drop support for version <= 6, we can simplify the code
// a bit since we don't need to worry about cycles.
}
nlohmann::json LockFile::toJson() const
@ -116,8 +139,16 @@ nlohmann::json LockFile::toJson() const
if (!node->inputs.empty()) {
auto inputs = nlohmann::json::object();
for (auto & i : node->inputs)
inputs[i.first] = dumpNode(i.first, i.second);
for (auto & i : node->inputs) {
if (auto child = std::get_if<0>(&i.second)) {
inputs[i.first] = dumpNode(i.first, *child);
} else if (auto follows = std::get_if<1>(&i.second)) {
auto arr = nlohmann::json::array();
for (auto & x : *follows)
arr.push_back(x);
inputs[i.first] = std::move(arr);
}
}
n["inputs"] = std::move(inputs);
}
@ -133,7 +164,7 @@ nlohmann::json LockFile::toJson() const
};
nlohmann::json json;
json["version"] = 6;
json["version"] = 7;
json["root"] = dumpNode("root", root);
json["nodes"] = std::move(nodes);
@ -172,7 +203,9 @@ bool LockFile::isImmutable() const
visit = [&](std::shared_ptr<const Node> node)
{
if (!nodes.insert(node).second) return;
for (auto & i : node->inputs) visit(i.second);
for (auto & i : node->inputs)
if (auto child = std::get_if<0>(&i.second))
visit(*child);
};
visit(root);
@ -216,9 +249,11 @@ static void flattenLockFile(
for (auto &[id, input] : node->inputs) {
auto inputPath(prefix);
inputPath.push_back(id);
if (auto lockedInput = std::dynamic_pointer_cast<const LockedNode>(input))
res.emplace(inputPath, lockedInput);
flattenLockFile(input, inputPath, done, res);
if (auto child = std::get_if<0>(&input)) {
if (auto lockedInput = std::dynamic_pointer_cast<const LockedNode>(*child))
res.emplace(inputPath, lockedInput);
flattenLockFile(*child, inputPath, done, res);
}
}
}