move root ID parsing and rendering into BackingStore

Summary:
The meaning of the root ID is defined by the BackingStore, so move
parsing and rendering into the BackingStore interface.

Reviewed By: xavierd

Differential Revision: D28560426

fbshipit-source-id: 7cfed4870d48016811b604348742754f6cdbd842

eden/fs/inodes/GlobNode.cpp

@@ -316,7 +316,7 @@ Future<vector<GlobNode::GlobResult>> GlobNode::evaluateImpl(
         if ((!node->children_.empty() || !node->recursiveChildren_.empty()) &&
             root.entryIsTree(entry)) {
           if (root.entryShouldLoadChildTree(entry)) {
-            recurse.emplace_back(std::make_pair(name, node));
+            recurse.emplace_back(name, node);
           } else {
             futures.emplace_back(
                 store->getTree(root.entryHash(entry), context)

eden/fs/journal/Journal.cpp

@@ -484,7 +484,8 @@ std::unique_ptr<JournalDeltaRange> Journal::accumulateRange(
 std::vector<DebugJournalDelta> Journal::getDebugRawJournalInfo(
     SequenceNumber from,
     std::optional<size_t> limit,
-    long mountGeneration) const {
+    long mountGeneration,
+    RootIdCodec& rootIdCodec) const {
   auto result = std::vector<DebugJournalDelta>();
   auto deltaState = deltaState_.lock();
   Hash currentHash = deltaState->currentHash;
@@ -492,19 +493,18 @@ std::vector<DebugJournalDelta> Journal::getDebugRawJournalInfo(
       *deltaState,
       from,
       limit,
-      [mountGeneration, &result, &currentHash](
-          const FileChangeJournalDelta& current) -> void {
+      [&](const FileChangeJournalDelta& current) -> void {
         DebugJournalDelta delta;
         JournalPosition fromPosition;
         fromPosition.mountGeneration_ref() = mountGeneration;
         fromPosition.sequenceNumber_ref() = current.sequenceID;
-        fromPosition.snapshotHash_ref() = thriftHash(currentHash);
+        fromPosition.snapshotHash_ref() = rootIdCodec.renderRootId(currentHash);
         delta.fromPosition_ref() = fromPosition;
 
         JournalPosition toPosition;
         toPosition.mountGeneration_ref() = mountGeneration;
         toPosition.sequenceNumber_ref() = current.sequenceID;
-        toPosition.snapshotHash_ref() = thriftHash(currentHash);
+        toPosition.snapshotHash_ref() = rootIdCodec.renderRootId(currentHash);
         delta.toPosition_ref() = toPosition;
 
         for (const auto& entry : current.getChangedFilesInOverlay()) {
@@ -520,19 +520,19 @@ std::vector<DebugJournalDelta> Journal::getDebugRawJournalInfo(
 
         result.push_back(delta);
       },
-      [mountGeneration, &result, &currentHash](
-          const HashUpdateJournalDelta& current) -> void {
+      [&](const HashUpdateJournalDelta& current) -> void {
         DebugJournalDelta delta;
         JournalPosition fromPosition;
         fromPosition.mountGeneration_ref() = mountGeneration;
         fromPosition.sequenceNumber_ref() = current.sequenceID;
-        fromPosition.snapshotHash_ref() = thriftHash(current.fromHash);
+        fromPosition.snapshotHash_ref() =
+            rootIdCodec.renderRootId(current.fromHash);
         delta.fromPosition_ref() = fromPosition;
 
         JournalPosition toPosition;
         toPosition.mountGeneration_ref() = mountGeneration;
         toPosition.sequenceNumber_ref() = current.sequenceID;
-        toPosition.snapshotHash_ref() = thriftHash(currentHash);
+        toPosition.snapshotHash_ref() = rootIdCodec.renderRootId(currentHash);
         delta.toPosition_ref() = toPosition;
         currentHash = current.fromHash;
 

eden/fs/journal/Journal.h

@@ -15,6 +15,7 @@
 #include <optional>
 #include <unordered_map>
 #include "eden/fs/journal/JournalDelta.h"
+#include "eden/fs/model/RootId.h"
 #include "eden/fs/service/ThriftUtil.h"
 #include "eden/fs/service/gen-cpp2/StreamingEdenService.h"
 #include "eden/fs/telemetry/EdenStats.h"
@@ -164,7 +165,8 @@ class Journal {
   std::vector<DebugJournalDelta> getDebugRawJournalInfo(
       SequenceNumber from,
       std::optional<size_t> limit,
-      long mountGeneration) const;
+      long mountGeneration,
+      RootIdCodec& rootIdCodec) const;
 
   /** Removes all prior contents from the journal and sets up the journal in a
    * way such that when subscribers are notified they all get truncated results

eden/fs/journal/test/JournalTest.cpp

@@ -6,9 +6,12 @@
  */
 
 #include "eden/fs/journal/Journal.h"
+
 #include <folly/portability/GTest.h>
 #include <gmock/gmock.h>
 
+#include "eden/fs/model/RootId.h"
+
 using namespace facebook::eden;
 
 namespace {
@@ -16,6 +19,7 @@ namespace {
 struct JournalTest : ::testing::Test {
   std::shared_ptr<EdenStats> edenStats{std::make_shared<EdenStats>()};
   Journal journal{edenStats};
+  HashRootIdCodec codec;
 };
 
 } // namespace
@@ -196,7 +200,7 @@ TEST_F(JournalTest, debugRawJournalInfoRemoveCreateUpdate) {
 
   long mountGen = 333;
 
-  auto debugDeltas = journal.getDebugRawJournalInfo(0, 3, mountGen);
+  auto debugDeltas = journal.getDebugRawJournalInfo(0, 3, mountGen, codec);
   ASSERT_EQ(3, debugDeltas.size());
 
   // Debug Raw Journal Info returns info from newest->latest
@@ -222,7 +226,7 @@ TEST_F(JournalTest, debugRawJournalInfoRemoveCreateUpdate) {
       *debugDeltas[2].fromPosition_ref()->mountGeneration_ref(), mountGen);
   EXPECT_EQ(*debugDeltas[2].fromPosition_ref()->sequenceNumber_ref(), 1);
 
-  debugDeltas = journal.getDebugRawJournalInfo(0, 1, mountGen);
+  debugDeltas = journal.getDebugRawJournalInfo(0, 1, mountGen, codec);
   ASSERT_EQ(1, debugDeltas.size());
   EXPECT_TRUE(
       *debugDeltas[0].changedPaths_ref()["test.txt"].existedBefore_ref());
@@ -232,7 +236,7 @@ TEST_F(JournalTest, debugRawJournalInfoRemoveCreateUpdate) {
       *debugDeltas[0].fromPosition_ref()->mountGeneration_ref(), mountGen);
   EXPECT_EQ(*debugDeltas[0].fromPosition_ref()->sequenceNumber_ref(), 3);
 
-  debugDeltas = journal.getDebugRawJournalInfo(0, 0, mountGen);
+  debugDeltas = journal.getDebugRawJournalInfo(0, 0, mountGen, codec);
   ASSERT_EQ(0, debugDeltas.size());
 }
 
@@ -250,7 +254,7 @@ TEST_F(JournalTest, debugRawJournalInfoHashUpdates) {
 
   long mountGen = 333;
 
-  auto debugDeltas = journal.getDebugRawJournalInfo(0, 3, mountGen);
+  auto debugDeltas = journal.getDebugRawJournalInfo(0, 3, mountGen, codec);
   ASSERT_EQ(3, debugDeltas.size());
 
   // Debug Raw Journal Info returns info from newest->latest

eden/fs/model/RootId.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This software may be used and distributed according to the terms of the
+ * GNU General Public License version 2.
+ */
+
+#pragma once
+
+#include "eden/fs/model/Hash.h"
+
+namespace facebook::eden {
+
+// TODO: This will be expanded to a variable-width type soon.
+using RootId = Hash;
+
+/**
+ * The meaning of a RootId is defined by the BackingStore implementation. Allow
+ * it to also define how how root IDs are parsed and rendered at API boundaries
+ * such as Thrift.
+ */
+class RootIdCodec {
+ public:
+  virtual ~RootIdCodec() = default;
+  virtual RootId parseRootId(folly::StringPiece rootId) = 0;
+  virtual std::string renderRootId(const RootId& rootId) = 0;
+};
+
+} // namespace facebook::eden

eden/fs/service/EdenServiceHandler.cpp

@@ -446,11 +446,11 @@ void EdenServiceHandler::checkOutRevision(
       *mountPoint,
       logHash(*hash),
       apache::thrift::util::enumName(checkoutMode, "(unknown)"));
-  auto hashObj = hashFromThrift(*hash);
 
   auto edenMount = server_->getMount(*mountPoint);
+  auto rootId = edenMount->getObjectStore()->parseRootId(*hash);
   auto checkoutFuture = edenMount->checkout(
-      hashObj,
+      rootId,
       helper->getFetchContext().getClientPid(),
       helper->getFunctionName(),
       checkoutMode);
@@ -462,8 +462,9 @@ void EdenServiceHandler::resetParentCommits(
     std::unique_ptr<WorkingDirectoryParents> parents) {
   auto helper = INSTRUMENT_THRIFT_CALL(
       DBG1, *mountPoint, logHash(*parents->parent1_ref()));
-  Hash parent1 = hashFromThrift(*parents->parent1_ref());
   auto edenMount = server_->getMount(*mountPoint);
+  auto parent1 =
+      edenMount->getObjectStore()->parseRootId(*parents->parent1_ref());
   edenMount->resetParent(parent1);
 }
 
@@ -571,10 +572,12 @@ void EdenServiceHandler::getCurrentJournalPosition(
   *out.mountGeneration_ref() = edenMount->getMountGeneration();
   if (latest) {
     out.sequenceNumber_ref() = latest->sequenceID;
-    out.snapshotHash_ref() = thriftHash(latest->toHash);
+    out.snapshotHash_ref() =
+        edenMount->getObjectStore()->renderRootId(latest->toHash);
   } else {
     out.sequenceNumber_ref() = 0;
-    out.snapshotHash_ref() = thriftHash(kZeroHash);
+    out.snapshotHash_ref() =
+        edenMount->getObjectStore()->renderRootId(kZeroHash);
   }
 }
 
@@ -943,15 +946,17 @@ void EdenServiceHandler::getFilesChangedSince(
           "Journal entry range has been truncated.");
     }
 
+    RootIdCodec& rootIdCodec = *edenMount->getObjectStore();
+
     out.toPosition_ref()->sequenceNumber_ref() = summed->toSequence;
     out.toPosition_ref()->snapshotHash_ref() =
-        thriftHash(summed->snapshotTransitions.back());
+        rootIdCodec.renderRootId(summed->snapshotTransitions.back());
     out.toPosition_ref()->mountGeneration_ref() =
         edenMount->getMountGeneration();
 
     out.fromPosition_ref()->sequenceNumber_ref() = summed->fromSequence;
     out.fromPosition_ref()->snapshotHash_ref() =
-        thriftHash(summed->snapshotTransitions.front());
+        rootIdCodec.renderRootId(summed->snapshotTransitions.front());
     out.fromPosition_ref()->mountGeneration_ref() =
         *out.toPosition_ref()->mountGeneration_ref();
 
@@ -971,7 +976,7 @@ void EdenServiceHandler::getFilesChangedSince(
 
     out.snapshotTransitions_ref()->reserve(summed->snapshotTransitions.size());
     for (auto& hash : summed->snapshotTransitions) {
-      out.snapshotTransitions_ref()->push_back(thriftHash(hash));
+      out.snapshotTransitions_ref()->push_back(rootIdCodec.renderRootId(hash));
     }
   }
 }
@@ -1025,7 +1030,10 @@ void EdenServiceHandler::debugGetRawJournal(
   }
 
   out.allDeltas_ref() = edenMount->getJournal().getDebugRawJournalInfo(
-      *params->fromSequenceNumber_ref(), limitopt, mountGeneration);
+      *params->fromSequenceNumber_ref(),
+      limitopt,
+      mountGeneration,
+      *edenMount->getObjectStore());
 }
 
 folly::SemiFuture<std::unique_ptr<std::vector<EntryInformationOrError>>>
@@ -1165,8 +1173,8 @@ folly::Future<std::unique_ptr<Glob>> EdenServiceHandler::future_globFiles(
     globResults.reserve(rootHashes->size());
     originHashes->reserve(rootHashes->size());
     for (auto& rootHash : *rootHashes) {
-      const Hash& originHash =
-          originHashes->emplace_back(hashFromThrift(rootHash));
+      const Hash& originHash = originHashes->emplace_back(
+          edenMount->getObjectStore()->parseRootId(rootHash));
 
       globResults.emplace_back(
           edenMount->getObjectStore()
@@ -1369,14 +1377,14 @@ void EdenServiceHandler::async_tm_getScmStatusV2(
         folly::to<string>("listIgnored=", *params->listIgnored_ref()));
 
     auto mount = server_->getMount(*params->mountPoint_ref());
-    auto hash = hashFromThrift(*params->commit_ref());
+    auto rootId = mount->getObjectStore()->parseRootId(*params->commit_ref());
     const auto& enforceParents = server_->getServerState()
                                      ->getReloadableConfig()
                                      .getEdenConfig()
                                      ->enforceParents.getValue();
     return wrapFuture(
         std::move(helper),
-        mount->diff(hash, *params->listIgnored_ref(), enforceParents, request)
+        mount->diff(rootId, *params->listIgnored_ref(), enforceParents, request)
             .thenValue([this, mount](std::unique_ptr<ScmStatus>&& status) {
               auto result = std::make_unique<GetScmStatusResult>();
               *result->status_ref() = std::move(*status);
@@ -1410,7 +1418,7 @@ void EdenServiceHandler::async_tm_getScmStatus(
     // want to enforce that even for this call, if we confirm that all existing
     // callers of this method can deal with the error.
     auto mount = server_->getMount(*mountPoint);
-    auto hash = hashFromThrift(*commitHash);
+    auto hash = mount->getObjectStore()->parseRootId(*commitHash);
     return wrapFuture(
         std::move(helper),
         mount->diff(
@@ -1432,9 +1440,9 @@ EdenServiceHandler::future_getScmStatusBetweenRevisions(
       *mountPoint,
       folly::to<string>("oldHash=", logHash(*oldHash)),
       folly::to<string>("newHash=", logHash(*newHash)));
-  auto id1 = hashFromThrift(*oldHash);
-  auto id2 = hashFromThrift(*newHash);
   auto mount = server_->getMount(*mountPoint);
+  auto id1 = mount->getObjectStore()->parseRootId(*oldHash);
+  auto id2 = mount->getObjectStore()->parseRootId(*newHash);
   return wrapFuture(
       std::move(helper),
       diffCommitsForStatus(mount->getObjectStore(), id1, id2));
@@ -1447,7 +1455,7 @@ void EdenServiceHandler::debugGetScmTree(
     bool localStoreOnly) {
   auto helper = INSTRUMENT_THRIFT_CALL(DBG3, *mountPoint, logHash(*idStr));
   auto edenMount = server_->getMount(*mountPoint);
-  auto id = hashFromThrift(*idStr);
+  auto id = edenMount->getObjectStore()->parseRootId(*idStr);
 
   static auto context = ObjectFetchContext::getNullContextWithCauseDetail(
       "EdenServiceHandler::debugGetScmTree");
@@ -1484,7 +1492,7 @@ void EdenServiceHandler::debugGetScmBlob(
     bool localStoreOnly) {
   auto helper = INSTRUMENT_THRIFT_CALL(DBG3, *mountPoint, logHash(*idStr));
   auto edenMount = server_->getMount(*mountPoint);
-  auto id = hashFromThrift(*idStr);
+  auto id = edenMount->getObjectStore()->parseRootId(*idStr);
 
   static auto context = ObjectFetchContext::getNullContextWithCauseDetail(
       "EdenServiceHandler::debugGetScmBlob");
@@ -1515,7 +1523,7 @@ void EdenServiceHandler::debugGetScmBlobMetadata(
     bool localStoreOnly) {
   auto helper = INSTRUMENT_THRIFT_CALL(DBG3, *mountPoint, logHash(*idStr));
   auto edenMount = server_->getMount(*mountPoint);
-  auto id = hashFromThrift(*idStr);
+  auto id = edenMount->getObjectStore()->parseRootId(*idStr);
 
   static auto context = ObjectFetchContext::getNullContextWithCauseDetail(
       "EdenServiceHandler::debugGetScmBlobMetadata");

eden/fs/service/ThriftUtil.h

@@ -12,11 +12,11 @@
 #include <string>
 
 #include "eden/fs/model/Hash.h"
+#include "eden/fs/model/RootId.h"
 #include "eden/fs/service/gen-cpp2/eden_types.h"
 #include "eden/fs/utils/EdenError.h"
 
-namespace facebook {
-namespace eden {
+namespace facebook::eden {
 
 /**
  * Convert a Hash to a std::string to be returned via thrift as a thrift
@@ -43,7 +43,7 @@ inline std::string thriftHash(const std::optional<Hash>& hash) {
  * This allows the input to be either a 20-byte binary string, or a 40-byte
  * hexadecimal string.
  */
-inline Hash hashFromThrift(const std::string& commitID) {
+inline Hash hashFromThrift(folly::StringPiece commitID) {
   if (commitID.size() == Hash::RAW_SIZE) {
     // This looks like 20 bytes of binary data.
     return Hash(folly::ByteRange(folly::StringPiece(commitID)));
@@ -60,5 +60,15 @@ inline Hash hashFromThrift(const std::string& commitID) {
         "\"");
   }
 }
-} // namespace eden
-} // namespace facebook
+
+class HashRootIdCodec : public RootIdCodec {
+ public:
+  Hash parseRootId(folly::StringPiece piece) override {
+    return hashFromThrift(piece);
+  }
+  std::string renderRootId(const Hash& rootId) override {
+    return thriftHash(rootId);
+  }
+};
+
+} // namespace facebook::eden

eden/fs/store/BackingStore.h

@@ -11,6 +11,7 @@
 #include <folly/futures/Future.h>
 #include <memory>
 
+#include "eden/fs/model/RootId.h"
 #include "eden/fs/store/ImportPriority.h"
 #include "eden/fs/store/ObjectFetchContext.h"
 
@@ -19,12 +20,12 @@ template <typename T>
 class Future;
 }
 
-namespace facebook {
-namespace eden {
+namespace facebook::eden {
 
 class Blob;
 class Hash;
 class Tree;
+
 /**
  * Abstract interface for a BackingStore.
  *
@@ -34,7 +35,7 @@ class Tree;
  * BackingStore implementations must be thread-safe, and perform their own
  * internal locking.
  */
-class BackingStore {
+class BackingStore : public RootIdCodec {
  public:
   BackingStore() {}
   virtual ~BackingStore() {}
@@ -81,5 +82,5 @@ class BackingStore {
   BackingStore(BackingStore const&) = delete;
   BackingStore& operator=(BackingStore const&) = delete;
 };
-} // namespace eden
-} // namespace facebook
+
+} // namespace facebook::eden

eden/fs/store/EmptyBackingStore.cpp

@@ -24,6 +24,14 @@ EmptyBackingStore::EmptyBackingStore() {}
 
 EmptyBackingStore::~EmptyBackingStore() {}
 
+Hash EmptyBackingStore::parseRootId(folly::StringPiece /*rootId*/) {
+  throw std::domain_error("empty backing store");
+}
+
+std::string EmptyBackingStore::renderRootId(const Hash& /*rootId*/) {
+  throw std::domain_error("empty backing store");
+}
+
 SemiFuture<unique_ptr<Tree>> EmptyBackingStore::getTree(
     const Hash& /* id */,
     ObjectFetchContext& /* context */) {

eden/fs/store/EmptyBackingStore.h

@@ -17,11 +17,14 @@ namespace eden {
  * A dummy BackingStore implementation, that always throws std::domain_error
  * for any ID that is looked up.
  */
-class EmptyBackingStore : public BackingStore {
+class EmptyBackingStore final : public BackingStore {
  public:
   EmptyBackingStore();
   ~EmptyBackingStore() override;
 
+  Hash parseRootId(folly::StringPiece rootId) override;
+  std::string renderRootId(const Hash& rootId) override;
+
   folly::SemiFuture<std::unique_ptr<Tree>> getTree(
       const Hash& id,
       ObjectFetchContext& context) override;

eden/fs/store/ObjectStore.cpp

@@ -104,6 +104,14 @@ void ObjectStore::deprioritizeWhenFetchHeavy(
   }
 }
 
+Hash ObjectStore::parseRootId(folly::StringPiece rootId) {
+  return backingStore_->parseRootId(rootId);
+}
+
+std::string ObjectStore::renderRootId(const Hash& rootId) {
+  return backingStore_->renderRootId(rootId);
+}
+
 Future<shared_ptr<const Tree>> ObjectStore::getTree(
     const Hash& id,
     ObjectFetchContext& fetchContext) const {

eden/fs/store/ObjectStore.h

@@ -16,6 +16,7 @@
 #include <folly/logging/xlog.h>
 #include "eden/fs/config/EdenConfig.h"
 #include "eden/fs/model/Hash.h"
+#include "eden/fs/model/RootId.h"
 #include "eden/fs/store/BlobMetadata.h"
 #include "eden/fs/store/IObjectStore.h"
 #include "eden/fs/store/ImportPriority.h"
@@ -70,6 +71,7 @@ constexpr uint64_t importPriorityDeprioritizeAmount{1};
  *   data, and may not be available during offline operation.
  */
 class ObjectStore : public IObjectStore,
+                    public RootIdCodec,
                     public std::enable_shared_from_this<ObjectStore> {
  public:
   static std::shared_ptr<ObjectStore> create(
@@ -108,6 +110,19 @@ class ObjectStore : public IObjectStore,
    */
   void deprioritizeWhenFetchHeavy(ObjectFetchContext& context) const;
 
+  /**
+   * Each BackingStore implementation defines its interpretation of root IDs.
+   * This function gives the BackingStore a chance to parse and canonicalize the
+   * root ID at API boundaries such as Thrift.
+   */
+  Hash parseRootId(folly::StringPiece rootId) override;
+
+  /**
+   * Each BackingStore defines the meaning and encoding of its root ID. Give it
+   * the chance to render a root ID to Thrift.
+   */
+  std::string renderRootId(const Hash& rootId) override;
+
   /**
    * Get a Tree by ID.
    *

eden/fs/store/git/GitBackingStore.cpp

@@ -17,6 +17,7 @@
 #include "eden/fs/model/Tree.h"
 #include "eden/fs/model/TreeEntry.h"
 #include "eden/fs/model/git/GitTree.h"
+#include "eden/fs/service/ThriftUtil.h"
 #include "eden/fs/store/LocalStore.h"
 #include "eden/fs/store/ObjectFetchContext.h"
 #include "eden/fs/utils/EnumValue.h"
@@ -74,6 +75,14 @@ const char* GitBackingStore::getPath() const {
   return git_repository_path(repo_);
 }
 
+Hash GitBackingStore::parseRootId(folly::StringPiece rootId) {
+  return hashFromThrift(rootId);
+}
+
+std::string GitBackingStore::renderRootId(const Hash& rootId) {
+  return thriftHash(rootId);
+}
+
 SemiFuture<unique_ptr<Tree>> GitBackingStore::getTree(
     const Hash& id,
     ObjectFetchContext& /*context*/) {

eden/fs/store/git/GitBackingStore.h

@@ -25,7 +25,7 @@ class LocalStore;
 /**
  * A BackingStore implementation that loads data out of a git repository.
  */
-class GitBackingStore : public BackingStore {
+class GitBackingStore final : public BackingStore {
  public:
   /**
    * Create a new GitBackingStore.
@@ -44,6 +44,9 @@ class GitBackingStore : public BackingStore {
    */
   const char* getPath() const;
 
+  Hash parseRootId(folly::StringPiece rootId) override;
+  std::string renderRootId(const Hash& rootId) override;
+
   folly::SemiFuture<std::unique_ptr<Tree>> getTree(
       const Hash& id,
       ObjectFetchContext& context) override;

eden/fs/store/hg/HgQueuedBackingStore.cpp

@@ -21,6 +21,7 @@
 
 #include "eden/fs/config/ReloadableConfig.h"
 #include "eden/fs/model/Blob.h"
+#include "eden/fs/service/ThriftUtil.h"
 #include "eden/fs/store/BackingStoreLogger.h"
 #include "eden/fs/store/LocalStore.h"
 #include "eden/fs/store/ObjectFetchContext.h"
@@ -261,6 +262,13 @@ void HgQueuedBackingStore::processRequest() {
   }
 }
 
+Hash HgQueuedBackingStore::parseRootId(folly::StringPiece rootId) {
+  return hashFromThrift(rootId);
+}
+std::string HgQueuedBackingStore::renderRootId(const Hash& rootId) {
+  return thriftHash(rootId);
+}
+
 folly::SemiFuture<std::unique_ptr<Tree>> HgQueuedBackingStore::getTree(
     const Hash& id,
     ObjectFetchContext& context) {

eden/fs/store/hg/HgQueuedBackingStore.h

@@ -96,7 +96,7 @@ struct HgImportTraceEvent : TraceEventBase {
  * these requests via different methods (reading from hgcache, Mononoke,
  * debugimporthelper, etc.).
  */
-class HgQueuedBackingStore : public BackingStore {
+class HgQueuedBackingStore final : public BackingStore {
  public:
   HgQueuedBackingStore(
       std::shared_ptr<LocalStore> localStore,
@@ -113,6 +113,9 @@ class HgQueuedBackingStore : public BackingStore {
     return *traceBus_;
   }
 
+  Hash parseRootId(folly::StringPiece rootId) override;
+  std::string renderRootId(const Hash& rootId) override;
+
   folly::SemiFuture<std::unique_ptr<Tree>> getTree(
       const Hash& id,
       ObjectFetchContext& context) override;

eden/fs/store/recas/ReCasBackingStore.cpp

@@ -11,35 +11,40 @@
 #include "eden/fs/model/Blob.h"
 #include "eden/fs/model/Hash.h"
 #include "eden/fs/model/Tree.h"
+#include "eden/fs/service/ThriftUtil.h"
 #include "eden/fs/store/LocalStore.h"
 
-namespace facebook {
-namespace eden {
+namespace facebook::eden {
 
 ReCasBackingStore::ReCasBackingStore(
-    std::shared_ptr<LocalStore> /** localStore **/) {
-  return;
-};
-ReCasBackingStore::~ReCasBackingStore() {
-  return;
-};
+    std::shared_ptr<LocalStore> /** localStore **/) {}
+
+ReCasBackingStore::~ReCasBackingStore() = default;
+
+Hash ReCasBackingStore::parseRootId(folly::StringPiece rootId) {
+  return hashFromThrift(rootId);
+}
+
+std::string ReCasBackingStore::renderRootId(const Hash& rootId) {
+  return thriftHash(rootId);
+}
 
 folly::SemiFuture<std::unique_ptr<Tree>> ReCasBackingStore::getTree(
     const Hash& /** id **/,
     ObjectFetchContext& /** context **/) {
   throw std::domain_error("unimplemented:");
-};
+}
+
 folly::SemiFuture<std::unique_ptr<Blob>> ReCasBackingStore::getBlob(
     const Hash& /** id **/,
     ObjectFetchContext& /** context **/) {
   throw std::domain_error("unimplemented");
-};
+}
 
 folly::SemiFuture<std::unique_ptr<Tree>> ReCasBackingStore::getTreeForCommit(
     const Hash& /** id **/,
     ObjectFetchContext& /** context **/) {
   throw std::domain_error("unimplemented");
-};
+}
 
-} // namespace eden
-} // namespace facebook
+} // namespace facebook::eden

eden/fs/store/recas/ReCasBackingStore.h

@@ -15,11 +15,14 @@ namespace eden {
 class Hash;
 class LocalStore;
 
-class ReCasBackingStore : public BackingStore {
+class ReCasBackingStore final : public BackingStore {
  public:
   explicit ReCasBackingStore(std::shared_ptr<LocalStore> localStore);
   ~ReCasBackingStore() override;
 
+  Hash parseRootId(folly::StringPiece rootId) override;
+  std::string renderRootId(const Hash& rootId) override;
+
   folly::SemiFuture<std::unique_ptr<Tree>> getTree(
       const Hash& id,
       ObjectFetchContext& context) override;

eden/fs/testharness/FakeBackingStore.cpp

@@ -16,6 +16,7 @@
 #include "eden/fs/model/Blob.h"
 #include "eden/fs/model/Hash.h"
 #include "eden/fs/model/Tree.h"
+#include "eden/fs/service/ThriftUtil.h"
 #include "eden/fs/store/LocalStore.h"
 #include "eden/fs/testharness/FakeTreeBuilder.h"
 #include "eden/fs/testharness/TestUtil.h"
@@ -35,7 +36,15 @@ namespace eden {
 FakeBackingStore::FakeBackingStore(std::shared_ptr<LocalStore> localStore)
     : localStore_(std::move(localStore)) {}
 
-FakeBackingStore::~FakeBackingStore() {}
+FakeBackingStore::~FakeBackingStore() = default;
+
+Hash FakeBackingStore::parseRootId(folly::StringPiece rootId) {
+  return hashFromThrift(rootId);
+}
+
+std::string FakeBackingStore::renderRootId(const Hash& rootId) {
+  return thriftHash(rootId);
+}
 
 SemiFuture<unique_ptr<Tree>> FakeBackingStore::getTree(
     const Hash& id,

eden/fs/testharness/FakeBackingStore.h

@@ -28,7 +28,7 @@ class LocalStore;
 /**
  * A BackingStore implementation for test code.
  */
-class FakeBackingStore : public BackingStore {
+class FakeBackingStore final : public BackingStore {
  public:
   struct TreeEntryData;
 
@@ -39,6 +39,9 @@ class FakeBackingStore : public BackingStore {
    * BackingStore APIs
    */
 
+  Hash parseRootId(folly::StringPiece rootId) override;
+  std::string renderRootId(const Hash& rootId) override;
+
   folly::SemiFuture<std::unique_ptr<Tree>> getTree(
       const Hash& id,
       ObjectFetchContext& context) override;

eden/fs/testharness/FakeObjectStore.cpp

@@ -9,18 +9,18 @@
 
 #include <folly/String.h>
 #include <folly/futures/Future.h>
+#include "eden/fs/service/ThriftUtil.h"
 
 using folly::Future;
 using folly::makeFuture;
 using std::make_shared;
 using std::shared_ptr;
 
-namespace facebook {
-namespace eden {
+namespace facebook::eden {
 
-FakeObjectStore::FakeObjectStore() {}
+FakeObjectStore::FakeObjectStore() = default;
 
-FakeObjectStore::~FakeObjectStore() {}
+FakeObjectStore::~FakeObjectStore() = default;
 
 void FakeObjectStore::addTree(Tree&& tree) {
   auto treeHash = tree.getHash();
@@ -92,5 +92,5 @@ size_t FakeObjectStore::getAccessCount(const Hash& hash) const {
     return 0;
   }
 }
-} // namespace eden
-} // namespace facebook
+
+} // namespace facebook::eden

eden/fs/testharness/FakeObjectStore.h

@@ -24,7 +24,7 @@ namespace eden {
  * Fake implementation of IObjectStore that allows the data to be injected
  * directly. This is designed to be used for unit tests.
  */
-class FakeObjectStore : public IObjectStore {
+class FakeObjectStore final : public IObjectStore {
  public:
   FakeObjectStore();
   ~FakeObjectStore() override;