Adapt scheduler to work with dynamic derivations

To avoid dealing with an optional `drvPath` (because we might not know
it yet) everywhere, make an `CreateDerivationAndRealiseGoal`. This goal
just builds/substitutes the derivation file, and then kicks of a build
for that obtained derivation; in other words it does the chaining of
goals when the drv file is missing (as can already be the case) or
computed (new case).

This also means the `getDerivation` state can be removed from
`DerivationGoal`, which makes the `BasicDerivation` / in memory case and
`Derivation` / drv file file case closer together.

The map type is factored out for clarity, and because we will soon hvae
a second use for it (`Derivation` itself).

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

1 files changed, 11 insertions, 4 deletions

diff --git a/src/libstore/build/derivation-goal.hh b/src/libstore/build/derivation-goal.hh
index 9d6fe1c0f..62b122c27 100644
--- a/src/libstore/build/derivation-goal.hh
+++ b/src/libstore/build/derivation-goal.hh
@@ -50,6 +50,13 @@ struct InitialOutput {
     std::optional<InitialOutputStatus> known;
 };
 
+/**
+ * A goal for building some or all of the outputs of a derivation.
+ *
+ * The derivation must already be present, either in the store in a drv
+ * or in memory. If the derivation itself needs to be gotten first, a
+ * `CreateDerivationAndRealiseGoal` goal must be used instead.
+ */
 struct DerivationGoal : public Goal
 {
     /**
@@ -66,8 +73,7 @@ struct DerivationGoal : public Goal
     std::shared_ptr<DerivationGoal> resolvedDrvGoal;
 
     /**
-     * The specific outputs that we need to build.  Empty means all of
-     * them.
+     * The specific outputs that we need to build.
      */
     OutputsSpec wantedOutputs;
 
@@ -229,7 +235,6 @@ struct DerivationGoal : public Goal
     /**
      * The states.
      */
-    void getDerivation();
     void loadDerivation();
     void haveDerivation();
     void outputsSubstitutionTried();
@@ -334,7 +339,9 @@ struct DerivationGoal : public Goal
 
     StorePathSet exportReferences(const StorePathSet & storePaths);
 
-    JobCategory jobCategory() override { return JobCategory::Build; };
+    JobCategory jobCategory() const override {
+        return JobCategory::Build;
+    };
 };
 
 MakeError(NotDeterministic, BuildError);