libstore: inline willBuildLocally and canBuildLocally into call sites

This commit inlines `DerivationOptions::willBuildLocally` and
`DerivationOptions::canBuildLocally` into their sole call site in
`DerivationBuildingGoal::tryToBuild`. The `canBuildLocally` logic is now
a lambda capturing the surrounding context, and `willBuildLocally` is
replaced by `drvOptions.preferLocalBuild && canBuildLocally`.

Progress on #5638

Co-authored-by: John Ericson <John.Ericson@Obsidian.Systems>

src/libstore-tests/derivation-advanced-attrs.cc

@@ -193,8 +193,6 @@ TYPED_TEST(DerivationAdvancedAttrsBothTest, advancedAttributes_defaults)
 
         EXPECT_EQ(options, advancedAttributes_defaults);
 
-        EXPECT_EQ(options.canBuildLocally(*this->store, got), false);
-        EXPECT_EQ(options.willBuildLocally(*this->store, got), false);
         EXPECT_EQ(options.substitutesAllowed(settings.getWorkerSettings()), true);
         EXPECT_EQ(options.useUidRange(got), false);
     });
@@ -335,8 +333,6 @@ TYPED_TEST(DerivationAdvancedAttrsBothTest, advancedAttributes_structuredAttrs_d
 
         EXPECT_EQ(options, advancedAttributes_structuredAttrs_defaults);
 
-        EXPECT_EQ(options.canBuildLocally(*this->store, got), false);
-        EXPECT_EQ(options.willBuildLocally(*this->store, got), false);
         EXPECT_EQ(options.substitutesAllowed(settings.getWorkerSettings()), true);
         EXPECT_EQ(options.useUidRange(got), false);
     });
@@ -402,8 +398,6 @@ TYPED_TEST(DerivationAdvancedAttrsBothTest, advancedAttributes_structuredAttrs)
 
         EXPECT_EQ(options, expected);
 
-        EXPECT_EQ(options.canBuildLocally(*this->store, got), false);
-        EXPECT_EQ(options.willBuildLocally(*this->store, got), false);
         EXPECT_EQ(options.substitutesAllowed(settings.getWorkerSettings()), false);
         EXPECT_EQ(options.useUidRange(got), true);
     });

src/libstore/build/derivation-building-goal.cc

@@ -325,10 +325,25 @@ Goal::Co DerivationBuildingGoal::tryToBuild(StorePathSet inputPaths)
             }
         }
 
+        bool canBuildLocally = [&] {
+            if (drv->platform != settings.thisSystem.get() && !settings.extraPlatforms.get().count(drv->platform)
+                && !drv->isBuiltin())
+                return false;
+
+            if (worker.settings.maxBuildJobs.get() == 0 && !drv->isBuiltin())
+                return false;
+
+            for (auto & feature : drvOptions.getRequiredSystemFeatures(*drv))
+                if (!worker.store.config.systemFeatures.get().count(feature))
+                    return false;
+
+            return true;
+        }();
+
         /* Don't do a remote build if the derivation has the attribute
            `preferLocalBuild' set.  Also, check and repair modes are only
            supported for local builds. */
-        bool buildLocally = (buildMode != bmNormal || drvOptions.willBuildLocally(worker.store, *drv))
+        bool buildLocally = (buildMode != bmNormal || (drvOptions.preferLocalBuild && canBuildLocally))
                             && worker.settings.maxBuildJobs.get() != 0;
 
         if (buildLocally) {
@@ -363,7 +378,7 @@ Goal::Co DerivationBuildingGoal::tryToBuild(StorePathSet inputPaths)
 
                 externalBuilder = settings.findExternalDerivationBuilderIfSupported(*drv);
 
-                if (!externalBuilder && !drvOptions.canBuildLocally(worker.store, *drv)) {
+                if (!externalBuilder && !canBuildLocally) {
                     auto msg =
                         fmt("Cannot build '%s'.\n"
                             "Reason: " ANSI_RED "required system or feature not available" ANSI_NORMAL

src/libstore/derivation-options.cc

@@ -6,7 +6,6 @@
 #include "nix/store/store-api.hh"
 #include "nix/util/types.hh"
 #include "nix/util/util.hh"
-#include "nix/store/globals.hh"
 #include "nix/util/variant-wrapper.hh"
 
 #include <optional>
@@ -359,29 +358,6 @@ StringSet DerivationOptions<Input>::getRequiredSystemFeatures(const BasicDerivat
     return res;
 }
 
-template<typename Input>
-bool DerivationOptions<Input>::canBuildLocally(Store & localStore, const BasicDerivation & drv) const
-{
-    if (drv.platform != settings.thisSystem.get() && !settings.extraPlatforms.get().count(drv.platform)
-        && !drv.isBuiltin())
-        return false;
-
-    if (settings.getWorkerSettings().maxBuildJobs.get() == 0 && !drv.isBuiltin())
-        return false;
-
-    for (auto & feature : getRequiredSystemFeatures(drv))
-        if (!localStore.config.systemFeatures.get().count(feature))
-            return false;
-
-    return true;
-}
-
-template<typename Input>
-bool DerivationOptions<Input>::willBuildLocally(Store & localStore, const BasicDerivation & drv) const
-{
-    return preferLocalBuild && canBuildLocally(localStore, drv);
-}
-
 template<typename Input>
 bool DerivationOptions<Input>::substitutesAllowed(const WorkerSettings & workerSettings) const
 {

src/libstore/include/nix/store/derivation-options.hh

@@ -14,7 +14,6 @@
 
 namespace nix {
 
-class Store;
 struct StoreDirConfig;
 struct BasicDerivation;
 struct StructuredAttrs;
@@ -184,16 +183,6 @@ struct DerivationOptions
      */
     StringSet getRequiredSystemFeatures(const BasicDerivation & drv) const;
 
-    /**
-     * @param drv See note on `getRequiredSystemFeatures`
-     */
-    bool canBuildLocally(Store & localStore, const BasicDerivation & drv) const;
-
-    /**
-     * @param drv See note on `getRequiredSystemFeatures`
-     */
-    bool willBuildLocally(Store & localStore, const BasicDerivation & drv) const;
-
     bool substitutesAllowed(const WorkerSettings & workerSettings) const;
 
     /**