Allow dynamic derivation deps in `inputDrvs`

We use the same nested map representation we used for goals, again in
order to save space. We might someday want to combine with `inputDrvs`,
by doing `V = bool` instead of `V = std::set<OutputName>`, but we are
not doing that yet for sake of a smaller diff.

The ATerm format for Derivations also needs to be extended, in addition
to the in-memory format. To accomodate this, we added a new basic
versioning scheme, so old versions of Nix will get nice errors. (And
going forward, if the ATerm format changes again the errors will be even
better.)

`parsedStrings`, an internal function used as part of parsing
derivations in A-Term format, used to consume the final `]` but expect
the initial `[` to already be consumed. This made for what looked like
unbalanced brackets at callsites, which was confusing. Now it consumes
both which is hopefully less confusing.

As part of testing, we also created a unit test for the A-Term format for
regular non-experimental derivations too.

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>

Apply suggestions from code review

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>

1 files changed, 28 insertions, 9 deletions

diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 66f319c3e..e2189fc66 100644
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -406,8 +406,22 @@ static void main_nix_build(int argc, char * * argv)
             }
         }
 
+        std::function<void(ref<SingleDerivedPath>, const DerivedPathMap<StringSet>::ChildNode &)> accumDerivedPath;
+
+        accumDerivedPath = [&](ref<SingleDerivedPath> inputDrv, const DerivedPathMap<StringSet>::ChildNode & inputNode) {
+            if (!inputNode.value.empty())
+                pathsToBuild.push_back(DerivedPath::Built {
+                    .drvPath = inputDrv,
+                    .outputs = OutputsSpec::Names { inputNode.value },
+                });
+            for (const auto & [outputName, childNode] : inputNode.childMap)
+                accumDerivedPath(
+                    make_ref<SingleDerivedPath>(SingleDerivedPath::Built { inputDrv, outputName }),
+                    childNode);
+        };
+
         // Build or fetch all dependencies of the derivation.
-        for (const auto & [inputDrv0, inputOutputs] : drv.inputDrvs) {
+        for (const auto & [inputDrv0, inputNode] : drv.inputDrvs.map) {
             // To get around lambda capturing restrictions in the
             // standard.
             const auto & inputDrv = inputDrv0;
@@ -416,10 +430,7 @@ static void main_nix_build(int argc, char * * argv)
                         return !std::regex_search(store->printStorePath(inputDrv), std::regex(exclude));
                     }))
             {
-                pathsToBuild.push_back(DerivedPath::Built {
-                    .drvPath = makeConstantStorePathRef(inputDrv),
-                    .outputs = OutputsSpec::Names { inputOutputs },
-                });
+                accumDerivedPath(makeConstantStorePathRef(inputDrv), inputNode);
                 pathsToCopy.insert(inputDrv);
             }
         }
@@ -482,13 +493,21 @@ static void main_nix_build(int argc, char * * argv)
 
         if (env.count("__json")) {
             StorePathSet inputs;
-            for (auto & [depDrvPath, wantedDepOutputs] : drv.inputDrvs) {
-                auto outputs = evalStore->queryPartialDerivationOutputMap(depDrvPath);
-                for (auto & i : wantedDepOutputs) {
+
+            std::function<void(const StorePath &, const DerivedPathMap<StringSet>::ChildNode &)> accumInputClosure;
+
+            accumInputClosure = [&](const StorePath & inputDrv, const DerivedPathMap<StringSet>::ChildNode & inputNode) {
+                auto outputs = evalStore->queryPartialDerivationOutputMap(inputDrv);
+                for (auto & i : inputNode.value) {
                     auto o = outputs.at(i);
                     store->computeFSClosure(*o, inputs);
                 }
-            }
+                for (const auto & [outputName, childNode] : inputNode.childMap)
+                    accumInputClosure(*outputs.at(outputName), childNode);
+            };
+
+            for (const auto & [inputDrv, inputNode] : drv.inputDrvs.map)
+                accumInputClosure(inputDrv, inputNode);
 
             ParsedDerivation parsedDrv(drvInfo.requireDrvPath(), drv);