Executor: Check validity of action outputs in compatible mode

This ensures that any entries that the standard remote execution
protocol accepts but are invalid in justbuild, i.e., upwards
symlinks, are rejected.

For this purpose, do not fail in the action response instances,
just perform the check there, as all required information is
available, and set a flag that the executor can check as needed.

1 files changed, 11 insertions, 3 deletions

diff --git a/src/buildtool/execution_api/remote/bazel/bazel_response.hpp b/src/buildtool/execution_api/remote/bazel/bazel_response.hpp
index df652141..55f45236 100644
--- a/src/buildtool/execution_api/remote/bazel/bazel_response.hpp
+++ b/src/buildtool/execution_api/remote/bazel/bazel_response.hpp
@@ -19,7 +19,7 @@
 #include <memory>
 #include <optional>
 #include <string>
-#include <utility>  // std::move
+#include <utility>  // std::move, std:pair
 
 #include <grpcpp/support/status.h>
 
@@ -91,6 +91,7 @@ class BazelResponse final : public IExecutionResponse {
         -> expected<gsl::not_null<ArtifactInfos const*>, std::string> final;
     auto DirectorySymlinks() noexcept
         -> expected<gsl::not_null<DirSymlinks const*>, std::string> final;
+    auto HasUpwardsSymlinks() noexcept -> expected<bool, std::string> final;
 
   private:
     std::string action_id_;
@@ -98,6 +99,7 @@ class BazelResponse final : public IExecutionResponse {
     BazelExecutionClient::ExecutionOutput output_{};
     ArtifactInfos artifacts_;
     DirSymlinks dir_symlinks_;
+    bool has_upwards_symlinks_ = false;  // only tracked in compatible mode
     bool populated_ = false;
 
     explicit BazelResponse(std::string action_id,
@@ -119,8 +121,14 @@ class BazelResponse final : public IExecutionResponse {
     /// \returns Error message on failure, nullopt on success.
     [[nodiscard]] auto Populate() noexcept -> std::optional<std::string>;
 
-    [[nodiscard]] auto UploadTreeMessageDirectories(bazel_re::Tree const& tree)
-        const -> expected<ArtifactDigest, std::string>;
+    /// \brief Tries to upload the tree rot and subdirectories. Performs also a
+    /// symlinks check.
+    /// \returns Pair of ArtifactDigest of root tree and flag signaling the
+    /// presence of any upwards symlinks on success, error message on failure.
+    [[nodiscard]] auto UploadTreeMessageDirectories(
+        bazel_re::Tree const& tree) const
+        -> expected<std::pair<ArtifactDigest, /*has_upwards_symlinks*/ bool>,
+                    std::string>;
 };
 
 #endif  // INCLUDED_SRC_BUILDTOOL_EXECUTION_API_REMOTE_BAZEL_BAZEL_RESPONSE_HPP