Move DerivationBuilder to its own file/header

The building logic is now free of the scheduling logic!

(The interface between them is just what is in the new header. This
makes it much easier to audit, and shrink over time.)

Author: Ericson2314

maintainers/flake-module.nix

@@ -284,6 +284,8 @@
               ''^src/libstore/build/goal\.cc$''
               ''^src/libstore/build/goal\.hh$''
               ''^src/libstore/unix/build/hook-instance\.cc$''
+              ''^src/libstore/unix/build/derivation-builder\.cc$''
+              ''^src/libstore/unix/build/derivation-builder\.hh$''
               ''^src/libstore/unix/build/local-derivation-goal\.cc$''
               ''^src/libstore/unix/build/local-derivation-goal\.hh$''
               ''^src/libstore/build/substitution-goal\.cc$''

src/libstore/build/derivation-building-misc.hh

@@ -0,0 +1,52 @@
+#pragma once
+/**
+ * @file Misc type defitions for both local building and remote (RPC building)
+ */
+
+#include "hash.hh"
+#include "path.hh"
+
+namespace nix {
+
+class Store;
+
+/**
+ * Unless we are repairing, we don't both to test validity and just assume it,
+ * so the choices are `Absent` or `Valid`.
+ */
+enum struct PathStatus {
+    Corrupt,
+    Absent,
+    Valid,
+};
+
+struct InitialOutputStatus
+{
+    StorePath path;
+    PathStatus status;
+    /**
+     * Valid in the store, and additionally non-corrupt if we are repairing
+     */
+    bool isValid() const
+    {
+        return status == PathStatus::Valid;
+    }
+    /**
+     * Merely present, allowed to be corrupt
+     */
+    bool isPresent() const
+    {
+        return status == PathStatus::Corrupt || status == PathStatus::Valid;
+    }
+};
+
+struct InitialOutput
+{
+    bool wanted;
+    Hash outputHash;
+    std::optional<InitialOutputStatus> known;
+};
+
+void runPostBuildHook(Store & store, Logger & logger, const StorePath & drvPath, const StorePathSet & outputPaths);
+
+}

src/libstore/build/derivation-goal.cc

@@ -5,31 +5,17 @@
 #include "processes.hh"
 #include "config-global.hh"
 #include "worker.hh"
-#include "builtins.hh"
-#include "builtins/buildenv.hh"
-#include "references.hh"
-#include "finally.hh"
 #include "util.hh"
-#include "archive.hh"
 #include "compression.hh"
 #include "common-protocol.hh"
 #include "common-protocol-impl.hh"
-#include "topo-sort.hh"
-#include "callback.hh"
 #include "local-store.hh" // TODO remove, along with remaining downcasts
 
-#include <regex>
-#include <queue>
-
 #include <fstream>
 #include <sys/types.h>
 #include <fcntl.h>
 #include <unistd.h>
 
-#ifndef _WIN32 // TODO abstract over proc exit status
-#  include <sys/wait.h>
-#endif
-
 #include <nlohmann/json.hpp>
 
 #include "strings.hh"

src/libstore/build/derivation-goal.hh

@@ -3,9 +3,7 @@
 
 #include "parsed-derivations.hh"
 #include "derivation-options.hh"
-#ifndef _WIN32
-#  include "user-lock.hh"
-#endif
+#include "derivation-building-misc.hh"
 #include "outputs-spec.hh"
 #include "store-api.hh"
 #include "pathlocks.hh"
@@ -21,40 +19,6 @@ struct HookInstance;
 
 typedef enum {rpAccept, rpDecline, rpPostpone} HookReply;
 
-/**
- * Unless we are repairing, we don't both to test validity and just assume it,
- * so the choices are `Absent` or `Valid`.
- */
-enum struct PathStatus {
-    Corrupt,
-    Absent,
-    Valid,
-};
-
-struct InitialOutputStatus {
-    StorePath path;
-    PathStatus status;
-    /**
-     * Valid in the store, and additionally non-corrupt if we are repairing
-     */
-    bool isValid() const {
-        return status == PathStatus::Valid;
-    }
-    /**
-     * Merely present, allowed to be corrupt
-     */
-    bool isPresent() const {
-        return status == PathStatus::Corrupt
-            || status == PathStatus::Valid;
-    }
-};
-
-struct InitialOutput {
-    bool wanted;
-    Hash outputHash;
-    std::optional<InitialOutputStatus> known;
-};
-
 /** Used internally */
 void runPostBuildHook(
     Store & store,
@@ -307,6 +271,4 @@ struct DerivationGoal : public Goal
     };
 };
 
-MakeError(NotDeterministic, BuildError);
-
 }

src/libstore/meson.build

@@ -256,6 +256,7 @@ include_dirs = [
 headers = [config_h] + files(
   'binary-cache-store.hh',
   'build-result.hh',
+  'build/derivation-building-misc.hh',
   'build/derivation-goal.hh',
   'build/drv-output-substitution-goal.hh',
   'build/goal.hh',