nix build --json: Include build statistics

Example:

  # nix build -L --extra-experimental-features cgroups --impure --expr 'with import <nixpkgs> {}; runCommand "foo" {} "dd if=/dev/urandom bs=1M count=1024 | md5sum; mkdir $out"' --json
  [
    {
      "cpuSystem": 1.911431,
      "cpuUser": 1.214249,
      "drvPath": "/nix/store/xzdqz67xba18hljhycp0hwfigzrs2z69-foo.drv",
      "outputs": {
        "out": "/nix/store/rh9mc9l2gkpq8kn2sgzndr6ll7ffjh6l-foo"
      },
      "startTime": 1669024076,
      "stopTime": 1669024079
    }
  ]

1 files changed, 8 insertions, 3 deletions

diff --git a/src/nix/app.cc b/src/nix/app.cc
index 48de8fb82..5658f2a52 100644
--- a/src/nix/app.cc
+++ b/src/nix/app.cc
@@ -37,11 +37,13 @@ struct InstallableDerivedPath : Installable
  * Return the rewrites that are needed to resolve a string whose context is
  * included in `dependencies`.
  */
-StringPairs resolveRewrites(Store & store, const BuiltPaths dependencies)
+StringPairs resolveRewrites(
+    Store & store,
+    const std::vector<BuiltPathWithResult> & dependencies)
 {
     StringPairs res;
     for (auto & dep : dependencies)
-        if (auto drvDep = std::get_if<BuiltPathBuilt>(&dep))
+        if (auto drvDep = std::get_if<BuiltPathBuilt>(&dep.path))
             for (auto & [ outputName, outputPath ] : drvDep->outputs)
                 res.emplace(
                     downstreamPlaceholder(store, drvDep->drvPath, outputName),
@@ -53,7 +55,10 @@ StringPairs resolveRewrites(Store & store, const BuiltPaths dependencies)
 /**
  * Resolve the given string assuming the given context.
  */
-std::string resolveString(Store & store, const std::string & toResolve, const BuiltPaths dependencies)
+std::string resolveString(
+    Store & store,
+    const std::string & toResolve,
+    const std::vector<BuiltPathWithResult> & dependencies)
 {
     auto rewrites = resolveRewrites(store, dependencies);
     return rewriteStrings(toResolve, rewrites);