diff options
Diffstat (limited to 'third_party/nix/src/nix/why-depends.cc')
| -rw-r--r-- | third_party/nix/src/nix/why-depends.cc | 267 |
1 files changed, 267 insertions, 0 deletions
diff --git a/third_party/nix/src/nix/why-depends.cc b/third_party/nix/src/nix/why-depends.cc new file mode 100644 index 000000000000..325a2be0a793 --- /dev/null +++ b/third_party/nix/src/nix/why-depends.cc @@ -0,0 +1,267 @@ +#include "command.hh" +#include "store-api.hh" +#include "progress-bar.hh" +#include "fs-accessor.hh" +#include "shared.hh" + +#include <queue> + +using namespace nix; + +static std::string hilite(const std::string & s, size_t pos, size_t len, + const std::string & colour = ANSI_RED) +{ + return + std::string(s, 0, pos) + + colour + + std::string(s, pos, len) + + ANSI_NORMAL + + std::string(s, pos + len); +} + +static std::string filterPrintable(const std::string & s) +{ + std::string res; + for (char c : s) + res += isprint(c) ? c : '.'; + return res; +} + +struct CmdWhyDepends : SourceExprCommand +{ + std::string _package, _dependency; + bool all = false; + + CmdWhyDepends() + { + expectArg("package", &_package); + expectArg("dependency", &_dependency); + + mkFlag() + .longName("all") + .shortName('a') + .description("show all edges in the dependency graph leading from 'package' to 'dependency', rather than just a shortest path") + .set(&all, true); + } + + std::string name() override + { + return "why-depends"; + } + + std::string description() override + { + return "show why a package has another package in its closure"; + } + + Examples examples() override + { + return { + Example{ + "To show one path through the dependency graph leading from Hello to Glibc:", + "nix why-depends nixpkgs.hello nixpkgs.glibc" + }, + Example{ + "To show all files and paths in the dependency graph leading from Thunderbird to libX11:", + "nix why-depends --all nixpkgs.thunderbird nixpkgs.xorg.libX11" + }, + Example{ + "To show why Glibc depends on itself:", + "nix why-depends nixpkgs.glibc nixpkgs.glibc" + }, + }; + } + + void run(ref<Store> store) override + { + auto package = parseInstallable(*this, store, _package, false); + auto packagePath = toStorePath(store, Build, package); + auto dependency = parseInstallable(*this, store, _dependency, false); + auto dependencyPath = toStorePath(store, NoBuild, dependency); + auto dependencyPathHash = storePathToHash(dependencyPath); + + PathSet closure; + store->computeFSClosure({packagePath}, closure, false, false); + + if (!closure.count(dependencyPath)) { + printError("'%s' does not depend on '%s'", package->what(), dependency->what()); + return; + } + + stopProgressBar(); // FIXME + + auto accessor = store->getFSAccessor(); + + auto const inf = std::numeric_limits<size_t>::max(); + + struct Node + { + Path path; + PathSet refs; + PathSet rrefs; + size_t dist = inf; + Node * prev = nullptr; + bool queued = false; + bool visited = false; + }; + + std::map<Path, Node> graph; + + for (auto & path : closure) + graph.emplace(path, Node{path, store->queryPathInfo(path)->references}); + + // Transpose the graph. + for (auto & node : graph) + for (auto & ref : node.second.refs) + graph[ref].rrefs.insert(node.first); + + /* Run Dijkstra's shortest path algorithm to get the distance + of every path in the closure to 'dependency'. */ + graph[dependencyPath].dist = 0; + + std::priority_queue<Node *> queue; + + queue.push(&graph.at(dependencyPath)); + + while (!queue.empty()) { + auto & node = *queue.top(); + queue.pop(); + + for (auto & rref : node.rrefs) { + auto & node2 = graph.at(rref); + auto dist = node.dist + 1; + if (dist < node2.dist) { + node2.dist = dist; + node2.prev = &node; + if (!node2.queued) { + node2.queued = true; + queue.push(&node2); + } + } + + } + } + + /* Print the subgraph of nodes that have 'dependency' in their + closure (i.e., that have a non-infinite distance to + 'dependency'). Print every edge on a path between `package` + and `dependency`. */ + std::function<void(Node &, const string &, const string &)> printNode; + + const string treeConn = "╠═══"; + const string treeLast = "╚═══"; + const string treeLine = "║ "; + const string treeNull = " "; + + struct BailOut { }; + + printNode = [&](Node & node, const string & firstPad, const string & tailPad) { + assert(node.dist != inf); + std::cout << fmt("%s%s%s%s" ANSI_NORMAL "\n", + firstPad, + node.visited ? "\e[38;5;244m" : "", + firstPad != "" ? "=> " : "", + node.path); + + if (node.path == dependencyPath && !all + && packagePath != dependencyPath) + throw BailOut(); + + if (node.visited) return; + node.visited = true; + + /* Sort the references by distance to `dependency` to + ensure that the shortest path is printed first. */ + std::multimap<size_t, Node *> refs; + std::set<std::string> hashes; + + for (auto & ref : node.refs) { + if (ref == node.path && packagePath != dependencyPath) continue; + auto & node2 = graph.at(ref); + if (node2.dist == inf) continue; + refs.emplace(node2.dist, &node2); + hashes.insert(storePathToHash(node2.path)); + } + + /* For each reference, find the files and symlinks that + contain the reference. */ + std::map<std::string, Strings> hits; + + std::function<void(const Path &)> visitPath; + + visitPath = [&](const Path & p) { + auto st = accessor->stat(p); + + auto p2 = p == node.path ? "/" : std::string(p, node.path.size() + 1); + + auto getColour = [&](const std::string & hash) { + return hash == dependencyPathHash ? ANSI_GREEN : ANSI_BLUE; + }; + + if (st.type == FSAccessor::Type::tDirectory) { + auto names = accessor->readDirectory(p); + for (auto & name : names) + visitPath(p + "/" + name); + } + + else if (st.type == FSAccessor::Type::tRegular) { + auto contents = accessor->readFile(p); + + for (auto & hash : hashes) { + auto pos = contents.find(hash); + if (pos != std::string::npos) { + size_t margin = 32; + auto pos2 = pos >= margin ? pos - margin : 0; + hits[hash].emplace_back(fmt("%s: …%s…\n", + p2, + hilite(filterPrintable( + std::string(contents, pos2, pos - pos2 + hash.size() + margin)), + pos - pos2, storePathHashLen, + getColour(hash)))); + } + } + } + + else if (st.type == FSAccessor::Type::tSymlink) { + auto target = accessor->readLink(p); + + for (auto & hash : hashes) { + auto pos = target.find(hash); + if (pos != std::string::npos) + hits[hash].emplace_back(fmt("%s -> %s\n", p2, + hilite(target, pos, storePathHashLen, getColour(hash)))); + } + } + }; + + // FIXME: should use scanForReferences(). + + visitPath(node.path); + + RunPager pager; + for (auto & ref : refs) { + auto hash = storePathToHash(ref.second->path); + + bool last = all ? ref == *refs.rbegin() : true; + + for (auto & hit : hits[hash]) { + bool first = hit == *hits[hash].begin(); + std::cout << tailPad + << (first ? (last ? treeLast : treeConn) : (last ? treeNull : treeLine)) + << hit; + if (!all) break; + } + + printNode(*ref.second, + tailPad + (last ? treeNull : treeLine), + tailPad + (last ? treeNull : treeLine)); + } + }; + + try { + printNode(graph.at(packagePath), "", ""); + } catch (BailOut & ) { } + } +}; + +static RegisterCommand r1(make_ref<CmdWhyDepends>()); |