exportReferencesGraph: Export more complete info in JSON format

This writes info about every path in the closure in the same format as
‘nix path-info --json’. Thus it also includes NAR hashes and sizes.

Example:

  [
    {
      "path": "/nix/store/10h6li26i7g6z3mdpvra09yyf10mmzdr-hello-2.10",
      "narHash": "sha256:0ckdc4z20kkmpqdilx0wl6cricxv90lh85xpv2qljppcmz6vzcxl",
      "narSize": 197648,
      "references": [
        "/nix/store/10h6li26i7g6z3mdpvra09yyf10mmzdr-hello-2.10",
        "/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24"
      ],
      "closureSize": 20939776
    },
    {
      "path": "/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24",
      "narHash": "sha256:1nfn3m3p98y1c0kd0brp80dn9n5mycwgrk183j17rajya0h7gax3",
      "narSize": 20742128,
      "references": [
        "/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24"
      ],
      "closureSize": 20742128
    }
  ]

Fixes #1134.

1 files changed, 11 insertions, 1 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index d76c8d1727fc..7fb5271f4a89 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -10,6 +10,7 @@
 #include "builtins.hh"
 #include "finally.hh"
 #include "compression.hh"
+#include "json.hh"
 
 #include <algorithm>
 #include <iostream>
@@ -2273,9 +2274,18 @@ void DerivationGoal::doExportReferencesGraph()
             }
         }
 
-        /* Write closure info to `fileName'. */
+        /* Write closure info to <fileName>. */
         writeFile(tmpDir + "/" + fileName,
             worker.store.makeValidityRegistration(paths, false, false));
+
+        /* Write a more comprehensive JSON serialisation to
+           <fileName>.json. */
+        std::ostringstream str;
+        {
+            JSONPlaceholder jsonRoot(str, true);
+            worker.store.pathInfoToJSON(jsonRoot, paths, false, true);
+        }
+        writeFile(tmpDir + "/" + fileName + ".json", str.str());
     }
 }