Faster flake.lock parsing

This PR reduces the creation of short-lived basic_json objects while
parsing flake.lock files. For large flake.lock files (~1.5MB) I was
observing ~60s being spent for trivial nix build operations while
after this change it is now taking ~1.6s.

(cherry picked from commit 7fd0de38c6)
(cherry picked from commit 89cadf5d64)
This commit is contained in:
Graham Dennis 2024-02-21 18:40:34 +11:00 committed by github-actions[bot]
parent 595b286f44
commit b12f1ffa7b

View File

@ -89,7 +89,7 @@ LockFile::LockFile(const nlohmann::json & json, const Path & path)
std::string inputKey = i.value();
auto k = nodeMap.find(inputKey);
if (k == nodeMap.end()) {
auto nodes = json["nodes"];
auto & nodes = json["nodes"];
auto jsonNode2 = nodes.find(inputKey);
if (jsonNode2 == nodes.end())
throw Error("lock file references missing node '%s'", inputKey);