Backport 'nix dev-shell' from the flakes branch

This also adds a '--profile' option to 'nix build' (replacing 'nix-env
--set').

1 files changed, 45 insertions, 0 deletions

diff --git a/src/nix/installables.hh b/src/nix/installables.hh
new file mode 100644
index 000000000..503984220
--- /dev/null
+++ b/src/nix/installables.hh
@@ -0,0 +1,45 @@
+#pragma once
+
+#include "util.hh"
+#include "path.hh"
+#include "eval.hh"
+
+#include <optional>
+
+namespace nix {
+
+struct Buildable
+{
+    std::optional<StorePath> drvPath;
+    std::map<std::string, StorePath> outputs;
+};
+
+typedef std::vector<Buildable> Buildables;
+
+struct Installable
+{
+    virtual ~Installable() { }
+
+    virtual std::string what() = 0;
+
+    virtual Buildables toBuildables()
+    {
+        throw Error("argument '%s' cannot be built", what());
+    }
+
+    Buildable toBuildable();
+
+    virtual std::pair<Value *, Pos> toValue(EvalState & state)
+    {
+        throw Error("argument '%s' cannot be evaluated", what());
+    }
+
+    /* Return a value only if this installable is a store path or a
+       symlink to it. */
+    virtual std::optional<StorePath> getStorePath()
+    {
+        return {};
+    }
+};
+
+}