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refactor(libstore): add BGL-based dependency graph for path analysis

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Introduces a reusable directed graph template built on Boost Graph Library
(BGL) to provide graph operations for store path dependency analysis. This
will be used by `nix why-depends` and future cycle detection.
This commit is contained in:
Bernardo Meurer Costa 2025-10-28 02:48:55 +00:00
parent dd0d006517
commit 13da1ca6d5
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7 changed files with 501 additions and 0 deletions
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97
src/libstore-tests/dependency-graph.cc Normal file
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#include "nix/store/dependency-graph-impl.hh"
#include <gtest/gtest.h>
namespace nix {
TEST(DependencyGraph, BasicAddEdge)
{
FilePathGraph depGraph;
depGraph.addEdge("a", "b");
depGraph.addEdge("b", "c");
EXPECT_TRUE(depGraph.hasNode("a"));
EXPECT_TRUE(depGraph.hasNode("b"));
EXPECT_TRUE(depGraph.hasNode("c"));
EXPECT_FALSE(depGraph.hasNode("d"));
// Verify edges using high-level API
auto successors = depGraph.getSuccessors("a");
EXPECT_EQ(successors.size(), 1);
EXPECT_EQ(successors[0], "b");
}
TEST(DependencyGraph, DfsTraversalOrder)
{
// Build a graph: A->B->D, A->C->D
// Successors should be visited in distance order (B and C before recursing)
FilePathGraph depGraph;
depGraph.addEdge("a", "b");
depGraph.addEdge("a", "c");
depGraph.addEdge("b", "d");
depGraph.addEdge("c", "d");
std::vector<std::string> visitedNodes;
std::vector<std::pair<std::string, std::string>> visitedEdges;
depGraph.dfsFromTarget(
"a",
"d",
[&](const std::string & node, size_t depth) {
visitedNodes.push_back(node);
return true;
},
[&](const std::string & from, const std::string & to, bool isLast, size_t depth) {
visitedEdges.emplace_back(from, to);
},
[](const std::string &) { return false; });
EXPECT_EQ(visitedNodes[0], "a");
// B and C both at distance 1, could be in either order
EXPECT_TRUE(
(visitedNodes[1] == "b" && visitedNodes[2] == "d") || (visitedNodes[1] == "c" && visitedNodes[2] == "d"));
}
TEST(DependencyGraph, GetSuccessors)
{
FilePathGraph depGraph;
depGraph.addEdge("a", "b");
depGraph.addEdge("a", "c");
auto successors = depGraph.getSuccessors("a");
EXPECT_EQ(successors.size(), 2);
EXPECT_TRUE(std::ranges::contains(successors, "b"));
EXPECT_TRUE(std::ranges::contains(successors, "c"));
}
TEST(DependencyGraph, GetAllNodes)
{
FilePathGraph depGraph;
depGraph.addEdge("foo", "bar");
depGraph.addEdge("bar", "baz");
auto nodes = depGraph.getAllNodes();
EXPECT_EQ(nodes.size(), 3);
EXPECT_TRUE(std::ranges::contains(nodes, "foo"));
EXPECT_TRUE(std::ranges::contains(nodes, "bar"));
EXPECT_TRUE(std::ranges::contains(nodes, "baz"));
}
TEST(DependencyGraph, ThrowsOnMissingNode)
{
FilePathGraph depGraph;
depGraph.addEdge("a", "b");
EXPECT_THROW(depGraph.getSuccessors("nonexistent"), nix::Error);
}
TEST(DependencyGraph, EmptyGraph)
{
FilePathGraph depGraph;
EXPECT_FALSE(depGraph.hasNode("anything"));
EXPECT_EQ(depGraph.numVertices(), 0);
EXPECT_EQ(depGraph.getAllNodes().size(), 0);
}
} // namespace nix