4 files changed, 25 insertions, 5 deletions
diff --git a/src/buildtool/common/TARGETS b/src/buildtool/common/TARGETS
index 1f280d78..4372db88 100644
--- a/src/buildtool/common/TARGETS
+++ b/src/buildtool/common/TARGETS
@@ -52,7 +52,7 @@
     , ["src/utils/cpp", "gsl"]
     , ["src/utils/cpp", "expected"]
     ]
-  , "private-deps": [["src/buildtool/crypto", "hasher"]]
+  , "private-deps": [["src/buildtool/crypto", "hasher"], "protocol_traits"]
   , "stage": ["src", "buildtool", "common"]
   }
 , "artifact_digest_factory":
@@ -68,7 +68,11 @@
     , ["src/utils/cpp", "expected"]
     ]
   , "private-deps":
-    ["bazel_digest_factory", "bazel_types", ["@", "gsl", "", "gsl"]]
+    [ "bazel_digest_factory"
+    , "bazel_types"
+    , ["@", "gsl", "", "gsl"]
+    , "protocol_traits"
+    ]
   , "stage": ["src", "buildtool", "common"]
   }
 , "common":
@@ -196,6 +200,7 @@
   { "type": ["@", "rules", "CC", "library"]
   , "name": ["protocol_traits"]
   , "hdrs": ["protocol_traits.hpp"]
+  , "deps": [["src/buildtool/crypto", "hash_function"]]
   , "stage": ["src", "buildtool", "common"]
   }
 }
diff --git a/src/buildtool/common/artifact_digest_factory.cpp b/src/buildtool/common/artifact_digest_factory.cpp
index dd9da28d..f3ea30c1 100644
--- a/src/buildtool/common/artifact_digest_factory.cpp
+++ b/src/buildtool/common/artifact_digest_factory.cpp
@@ -17,15 +17,17 @@
 #include "gsl/gsl"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
 #include "src/buildtool/common/bazel_types.hpp"
+#include "src/buildtool/common/protocol_traits.hpp"
 
 auto ArtifactDigestFactory::Create(HashFunction::Type hash_type,
                                    std::string hash,
                                    std::size_t size,
                                    bool is_tree) noexcept
     -> expected<ArtifactDigest, std::string> {
-    const bool kTreesAllowed = hash_type == HashFunction::Type::GitSHA1;
     auto hash_info =
-        HashInfo::Create(hash_type, std::move(hash), kTreesAllowed and is_tree);
+        HashInfo::Create(hash_type,
+                         std::move(hash),
+                         ProtocolTraits::IsTreeAllowed(hash_type) and is_tree);
     if (not hash_info) {
         return unexpected{std::move(hash_info).error()};
     }
diff --git a/src/buildtool/common/bazel_digest_factory.cpp b/src/buildtool/common/bazel_digest_factory.cpp
index 4ff885aa..3a1f8519 100644
--- a/src/buildtool/common/bazel_digest_factory.cpp
+++ b/src/buildtool/common/bazel_digest_factory.cpp
@@ -16,12 +16,13 @@
 
 #include <utility>
 
+#include "src/buildtool/common/protocol_traits.hpp"
 #include "src/buildtool/crypto/hasher.hpp"
 
 auto BazelDigestFactory::Create(HashInfo const& hash_info,
                                 std::int64_t size) noexcept
     -> bazel_re::Digest {
-    auto hash = hash_info.HashType() == HashFunction::Type::GitSHA1
+    auto hash = ProtocolTraits::IsNative(hash_info.HashType())
                     ? Prefix(hash_info.Hash(), hash_info.IsTree())
                     : hash_info.Hash();
 
diff --git a/src/buildtool/common/protocol_traits.hpp b/src/buildtool/common/protocol_traits.hpp
index 49850233..f1a51cbe 100644
--- a/src/buildtool/common/protocol_traits.hpp
+++ b/src/buildtool/common/protocol_traits.hpp
@@ -15,6 +15,8 @@
 #ifndef INCLUDED_SRC_BUILDTOOL_COMMON_PROTOCOL_TRAITS_HPP
 #define INCLUDED_SRC_BUILDTOOL_COMMON_PROTOCOL_TRAITS_HPP
 
+#include "src/buildtool/crypto/hash_function.hpp"
+
 class ProtocolTraits final {
   public:
     [[nodiscard]] static auto Instance() noexcept -> ProtocolTraits& {
@@ -26,6 +28,16 @@ class ProtocolTraits final {
     }
     void SetCompatible(bool value = true) noexcept { compatible_ = value; }
 
+    inline static constexpr auto IsNative(HashFunction::Type hash_type) noexcept
+        -> bool {
+        return hash_type == HashFunction::Type::GitSHA1;
+    }
+
+    inline static constexpr auto IsTreeAllowed(
+        HashFunction::Type hash_type) noexcept -> bool {
+        return IsNative(hash_type);
+    }
+
   private:
     bool compatible_ = false;
 };