serve service: Respond also with digest in serve repository tree RPCs

...besides the simple Git hash, if syncing was done. This way one
can know what digest to ask for from the remote. The serve client
also needs to now know what hash function the remote expects.

The serve service proto file is updated accordingly.

1 files changed, 26 insertions, 13 deletions

diff --git a/src/buildtool/serve_api/remote/source_tree_client.hpp b/src/buildtool/serve_api/remote/source_tree_client.hpp
index c849eeb3..39e0e721 100644
--- a/src/buildtool/serve_api/remote/source_tree_client.hpp
+++ b/src/buildtool/serve_api/remote/source_tree_client.hpp
@@ -16,12 +16,15 @@
 #define INCLUDED_SRC_BUILDTOOL_SERVE_API_SOURCE_TREE_CLIENT_HPP
 
 #include <memory>
+#include <optional>
 #include <string>
 #include <unordered_map>
 
 #include "gsl/gsl"
 #include "justbuild/just_serve/just_serve.grpc.pb.h"
+#include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/remote/remote_common.hpp"
+#include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/remote/context.hpp"
 #include "src/buildtool/file_system/git_types.hpp"
 #include "src/buildtool/file_system/symlinks_map/pragma_special.hpp"
@@ -34,19 +37,23 @@ class SourceTreeClient {
   public:
     explicit SourceTreeClient(
         ServerAddress const& address,
+        gsl::not_null<HashFunction const*> const& hash_function,
         gsl::not_null<RemoteContext const*> const& remote_context) noexcept;
 
-    // An error + data union type
-    using result_t = expected<std::string, GitLookupError>;
+    struct TreeResult {
+        std::string tree;
+        std::optional<ArtifactDigest> digest;
+    };
+    using result_t = expected<TreeResult, GitLookupError>;
 
     /// \brief Retrieve the Git tree of a given commit, if known by the
     /// endpoint. It is a fatal error if the commit is known to the endpoint but
-    /// no tree is able to be returned.
+    /// no result is able to be returned.
     /// \param[in] commit_id Hash of the Git commit to look up.
     /// \param[in] subdir Relative path of the tree inside commit.
     /// \param[in] sync_tree Sync tree to the remote-execution endpoint.
-    /// \returns The tree identifier on success or an unexpected error (fatal or
-    /// commit or subtree not found).
+    /// \returns The optional tree digest on success or an unexpected error
+    /// (fatal or commit or subtree not found).
     [[nodiscard]] auto ServeCommitTree(std::string const& commit_id,
                                        std::string const& subdir,
                                        bool sync_tree) const noexcept
@@ -54,15 +61,15 @@ class SourceTreeClient {
 
     /// \brief Retrieve the Git tree of an archive content, if known by the
     /// endpoint. It is a fatal error if the content blob is known to the
-    /// endpoint but no tree is able to be returned.
+    /// endpoint but no result is able to be returned.
     /// \param[in] content Hash of the archive content to look up.
     /// \param[in] archive_type Type of archive ("archive"|"zip").
     /// \param[in] subdir Relative path of the tree inside archive.
     /// \param[in] resolve_symlinks Optional enum to state how symlinks in the
     /// archive should be handled if the tree has to be actually computed.
     /// \param[in] sync_tree Sync tree to the remote-execution endpoint.
-    /// \returns The tree identifier on success or an unexpected error (fatal or
-    /// content blob not found).
+    /// \returns The optional tree digest on success or an unexpected error
+    /// (fatal or content blob not found).
     [[nodiscard]] auto ServeArchiveTree(
         std::string const& content,
         std::string const& archive_type,
@@ -72,20 +79,25 @@ class SourceTreeClient {
 
     /// \brief Retrieve the Git tree of a directory of distfiles, if all the
     /// content blobs are known by the endpoint. It is a fatal error if all
-    /// content blobs are known but no tree is able to be returned.
+    /// content blobs are known but no result is able to be returned.
     /// \param[in] distfiles Mapping from distfile names to content blob ids.
-    /// \param[in] sync_tree Sync tree and all ditfile blobs to the
+    /// \param[in] sync_tree Sync tree and all distfile blobs to the
     /// remote-execution endpoint.
-    /// \returns The tree identifier on success or an unexpected error (fatal or
-    /// at least one distfile blob missing).
+    /// \returns The optional tree digest on success or an unexpected error
+    /// (fatal or at least one distfile blob missing).
     [[nodiscard]] auto ServeDistdirTree(
         std::shared_ptr<std::unordered_map<std::string, std::string>> const&
             distfiles,
         bool sync_tree) const noexcept -> result_t;
 
     /// \brief Retrieve the Git tree of a foreign-file directory, if all content
-    /// blobs are known to the end point and, as a side effect, make that tree
+    /// blobs are known to the endpoint and, as a side-effect, make that tree
     /// known to the serve endpoint.
+    /// \param[in] content Hash of the foreign-file content.
+    /// \param[in] name Name of the foreign-file.
+    /// \param[in] executable Executable flag of foreign-file.
+    /// \returns The optional tree digest on success or an unexpected error
+    /// (fatal or content not found).
     [[nodiscard]] auto ServeForeignFileTree(const std::string& content,
                                             const std::string& name,
                                             bool executable) const noexcept
@@ -122,6 +134,7 @@ class SourceTreeClient {
         -> bool;
 
   private:
+    HashFunction const& hash_function_;  // hash function of the remote
     std::unique_ptr<justbuild::just_serve::SourceTree::Stub> stub_;
     Logger logger_{"RemoteSourceTreeClient"};
 };