1 files changed, 75 insertions, 0 deletions
diff --git a/third_party/nix/src/nix/edit.cc b/third_party/nix/src/nix/edit.cc
new file mode 100644
index 000000000000..04c67acb94c6
--- /dev/null
+++ b/third_party/nix/src/nix/edit.cc
@@ -0,0 +1,75 @@
+#include <absl/strings/str_split.h>
+#include <glog/logging.h>
+#include <unistd.h>
+
+#include "libexpr/attr-path.hh"
+#include "libexpr/eval.hh"
+#include "libmain/shared.hh"
+#include "nix/command.hh"
+
+namespace nix {
+struct CmdEdit final : InstallableCommand {
+  std::string name() override { return "edit"; }
+
+  std::string description() override {
+    return "open the Nix expression of a Nix package in $EDITOR";
+  }
+
+  Examples examples() override {
+    return {
+        Example{"To open the Nix expression of the GNU Hello package:",
+                "nix edit nixpkgs.hello"},
+    };
+  }
+
+  void run(ref<Store> store) override {
+    auto state = getEvalState();
+
+    auto v = installable->toValue(*state);
+
+    Value* v2;
+    try {
+      auto dummyArgs = Bindings::New();
+      v2 = findAlongAttrPath(*state, "meta.position", dummyArgs.get(), *v);
+    } catch (Error&) {
+      throw Error("package '%s' has no source location information",
+                  installable->what());
+    }
+
+    auto pos = state->forceString(*v2);
+    DLOG(INFO) << "position is " << pos;
+
+    auto colon = pos.rfind(':');
+    if (colon == std::string::npos) {
+      throw Error("cannot parse meta.position attribute '%s'", pos);
+    }
+
+    std::string filename(pos, 0, colon);
+    int lineno;
+    try {
+      lineno = std::stoi(std::string(pos, colon + 1));
+    } catch (std::invalid_argument& e) {
+      throw Error("cannot parse line number '%s'", pos);
+    }
+
+    auto editor = getEnv("EDITOR").value_or("cat");
+
+    Strings args =
+        absl::StrSplit(editor, absl::ByAnyChar(" \t\n\r"), absl::SkipEmpty());
+
+    if (editor.find("emacs") != std::string::npos ||
+        editor.find("nano") != std::string::npos ||
+        editor.find("vim") != std::string::npos) {
+      args.push_back(fmt("+%d", lineno));
+    }
+
+    args.push_back(filename);
+
+    execvp(args.front().c_str(), stringsToCharPtrs(args).data());
+
+    throw SysError("cannot run editor '%s'", editor);
+  }
+};
+}  // namespace nix
+
+static nix::RegisterCommand r1(nix::make_ref<nix::CmdEdit>());