Add "nix show-derivation"

This debug command prints a store derivation in JSON format. For
example:

  $ nix show-derivation nixpkgs.hello
  {
    "/nix/store/ayjwpwwiyy04nh9z71rsdgd3q7bra7ch-hello-2.10.drv": {
      "outputs": {
        "out": {
          "path": "/nix/store/w5w4v29ql0qwqhczkdxs94ix2lh7ibgs-hello-2.10"
        }
      },
      "inputSrcs": [
        "/nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25b-default-builder.sh"
      ],
      "inputDrvs": {
        "/nix/store/13839aqdf6x4k3b785rw5f2l7857l6y3-bash-4.4-p12.drv": [
          "out"
        ],
        "/nix/store/vgdx7fdc7d4iirmnwj2py1nrvr5qwzj7-hello-2.10.tar.gz.drv": [
          "out"
        ],
        "/nix/store/x3kkd0vsqfflbvwf1055l9mr39bg0ms0-stdenv.drv": [
          "out"
        ]
      },
      "platform": "x86_64-linux",
      "builder": "/nix/store/qp5fw57d38bd1n07ss4zxh88zg67c3vg-bash-4.4-p12/bin/bash",
      "args": [
        "-e",
        "/nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25b-default-builder.sh"
      ],
      "env": {
        "buildInputs": "",
        "builder": "/nix/store/qp5fw57d38bd1n07ss4zxh88zg67c3vg-bash-4.4-p12/bin/bash",
        "configureFlags": "",
        "doCheck": "1",
        "name": "hello-2.10",
        "nativeBuildInputs": "",
        "out": "/nix/store/w5w4v29ql0qwqhczkdxs94ix2lh7ibgs-hello-2.10",
        "propagatedBuildInputs": "",
        "propagatedNativeBuildInputs": "",
        "src": "/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz",
        "stdenv": "/nix/store/6zngq1rdh0ans9qyckqimqibgnlvlfrm-stdenv",
        "system": "x86_64-linux"
      }
    }
  }

This removes the need for pp-aterm.

1 files changed, 24 insertions, 0 deletions

diff --git a/src/nix/installables.cc b/src/nix/installables.cc
index 76df05fa3..b60f71b14 100644
--- a/src/nix/installables.cc
+++ b/src/nix/installables.cc
@@ -303,6 +303,30 @@ Path toStorePath(ref<Store> store, RealiseMode mode,
     return *paths.begin();
 }
 
+PathSet toDerivations(ref<Store> store,
+    std::vector<std::shared_ptr<Installable>> installables, bool useDeriver)
+{
+    PathSet drvPaths;
+
+    for (auto & i : installables)
+        for (auto & b : i->toBuildables()) {
+            if (b.drvPath.empty()) {
+                if (!useDeriver)
+                    throw Error("argument '%s' did not evaluate to a derivation", i->what());
+                for (auto & output : b.outputs) {
+                    auto derivers = store->queryValidDerivers(output.second);
+                    if (derivers.empty())
+                        throw Error("'%s' does not have a known deriver", i->what());
+                    // FIXME: use all derivers?
+                    drvPaths.insert(*derivers.begin());
+                }
+            } else
+                drvPaths.insert(b.drvPath);
+        }
+
+    return drvPaths;
+}
+
 void InstallablesCommand::prepare()
 {
     installables = parseInstallables(*this, getStore(), _installables, useDefaultInstallables());