Move `querySubstitutablePathInfos` from `LocalStore` to `Store`

The code is not local-store-specific, so we should share it with all
stores. More uniform behavior is better, and a less store-specific
functionality is more maintainable.

This fixes a FIXME added in f73d911628 by @edolstra himself.

1 files changed, 48 insertions, 0 deletions

diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 60e87918a..8fc3ed46a 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -507,6 +507,54 @@ StorePathSet Store::queryDerivationOutputs(const StorePath & path)
     return outputPaths;
 }
 
+
+void Store::querySubstitutablePathInfos(const StorePathCAMap & paths, SubstitutablePathInfos & infos)
+{
+    if (!settings.useSubstitutes) return;
+    for (auto & sub : getDefaultSubstituters()) {
+        for (auto & path : paths) {
+            if (infos.count(path.first))
+                // Choose first succeeding substituter.
+                continue;
+
+            auto subPath(path.first);
+
+            // Recompute store path so that we can use a different store root.
+            if (path.second) {
+                subPath = makeFixedOutputPathFromCA(path.first.name(), *path.second);
+                if (sub->storeDir == storeDir)
+                    assert(subPath == path.first);
+                if (subPath != path.first)
+                    debug("replaced path '%s' with '%s' for substituter '%s'", printStorePath(path.first), sub->printStorePath(subPath), sub->getUri());
+            } else if (sub->storeDir != storeDir) continue;
+
+            debug("checking substituter '%s' for path '%s'", sub->getUri(), sub->printStorePath(subPath));
+            try {
+                auto info = sub->queryPathInfo(subPath);
+
+                if (sub->storeDir != storeDir && !(info->isContentAddressed(*sub) && info->references.empty()))
+                    continue;
+
+                auto narInfo = std::dynamic_pointer_cast<const NarInfo>(
+                    std::shared_ptr<const ValidPathInfo>(info));
+                infos.insert_or_assign(path.first, SubstitutablePathInfo{
+                    info->deriver,
+                    info->references,
+                    narInfo ? narInfo->fileSize : 0,
+                    info->narSize});
+            } catch (InvalidPath &) {
+            } catch (SubstituterDisabled &) {
+            } catch (Error & e) {
+                if (settings.tryFallback)
+                    logError(e.info());
+                else
+                    throw;
+            }
+        }
+    }
+}
+
+
 bool Store::isValidPath(const StorePath & storePath)
 {
     {