Support `repairPath` on most stores.

More progress on issue #5729

The method trivially generalizes to be store-implementation-agnostic, in
fact.

However, we force it to continue to be unimplemented with `RemoteStore`
and `LegacySSHStore` because the implementation we'd get via the
generalization is probably not the one users expect. This keeps our
hands untied to do it right going forward.

For more about the tension between the scheduler logic being
store-type-agnostic and remote stores doing their own scheduling, see
issues #5025 and #5056.

5 files changed, 24 insertions, 5 deletions

diff --git a/src/libstore/build/entry-points.cc b/src/libstore/build/entry-points.cc
index 2925fe3ca..efa1445fa 100644
--- a/src/libstore/build/entry-points.cc
+++ b/src/libstore/build/entry-points.cc
@@ -119,7 +119,7 @@ void Store::ensurePath(const StorePath & path)
 }
 
 
-void LocalStore::repairPath(const StorePath & path)
+void Store::repairPath(const StorePath & path)
 {
     Worker worker(*this, *this);
     GoalPtr goal = worker.makePathSubstitutionGoal(path, Repair);
diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index d2ddbbe5f..2341d4cb2 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -345,6 +345,17 @@ public:
     virtual ref<FSAccessor> getFSAccessor() override
     { unsupported("getFSAccessor"); }
 
+    /**
+     * The default instance would schedule the work on the client side, but
+     * for consistency with `buildPaths` and `buildDerivation` it should happen
+     * on the remote side.
+     *
+     * We make this fail for now so we can add implement this properly later
+     * without it being a breaking change.
+     */
+    void repairPath(const StorePath & path) override
+    { unsupported("repairPath"); }
+
     void computeFSClosure(const StorePathSet & paths,
         StorePathSet & out, bool flipDirection = false,
         bool includeOutputs = false, bool includeDerivers = false) override
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 55add18dd..70debad38 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -240,8 +240,6 @@ public:
 
     void vacuumDB();
 
-    void repairPath(const StorePath & path) override;
-
     void addSignatures(const StorePath & storePath, const StringSet & sigs) override;
 
     /**
diff --git a/src/libstore/remote-store.hh b/src/libstore/remote-store.hh
index 1c45f543e..0da039837 100644
--- a/src/libstore/remote-store.hh
+++ b/src/libstore/remote-store.hh
@@ -136,6 +136,17 @@ public:
 
     bool verifyStore(bool checkContents, RepairFlag repair) override;
 
+    /**
+     * The default instance would schedule the work on the client side, but
+     * for consistency with `buildPaths` and `buildDerivation` it should happen
+     * on the remote side.
+     *
+     * We make this fail for now so we can add implement this properly later
+     * without it being a breaking change.
+     */
+    void repairPath(const StorePath & path) override
+    { unsupported("repairPath"); }
+
     void addSignatures(const StorePath & storePath, const StringSet & sigs) override;
 
     void queryMissing(const std::vector<DerivedPath> & targets,
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 5bee272bf..30c821c58 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -684,8 +684,7 @@ public:
      * Repair the contents of the given path by redownloading it using
      * a substituter (if available).
      */
-    virtual void repairPath(const StorePath & path)
-    { unsupported("repairPath"); }
+    virtual void repairPath(const StorePath & path);
 
     /**
      * Add signatures to the specified store path. The signatures are