2 files changed, 109 insertions, 0 deletions
diff --git a/src/buildtool/file_system/file_system_manager.hpp b/src/buildtool/file_system/file_system_manager.hpp
index 1be50ac0..0bdfb8a6 100644
--- a/src/buildtool/file_system/file_system_manager.hpp
+++ b/src/buildtool/file_system/file_system_manager.hpp
@@ -118,6 +118,34 @@ class FileSystemManager {
         }
     }
 
+    template <ObjectType kType>
+    requires(IsFileObject(kType))
+        [[nodiscard]] static auto CreateFileHardlinkAs(
+            std::filesystem::path const& file_path,
+            std::filesystem::path const& link_path) noexcept -> bool {
+        // Set permissions first (permissions are a property of the file) so
+        // that the created link has the correct permissions as soon as the link
+        // creation is finished.
+        return SetFilePermissions(file_path, IsExecutableObject(kType)) and
+               CreateFileHardlink(file_path, link_path);
+    }
+
+    [[nodiscard]] static auto CreateFileHardlinkAs(
+        std::filesystem::path const& file_path,
+        std::filesystem::path const& link_path,
+        ObjectType output_type) noexcept -> bool {
+        switch (output_type) {
+            case ObjectType::File:
+                return CreateFileHardlinkAs<ObjectType::File>(file_path,
+                                                              link_path);
+            case ObjectType::Executable:
+                return CreateFileHardlinkAs<ObjectType::Executable>(file_path,
+                                                                    link_path);
+            case ObjectType::Tree:
+                return false;
+        }
+    }
+
     [[nodiscard]] static auto Rename(std::filesystem::path const& src,
                                      std::filesystem::path const& dst,
                                      bool no_clobber = false) noexcept -> bool {
diff --git a/test/buildtool/file_system/file_system_manager.test.cpp b/test/buildtool/file_system/file_system_manager.test.cpp
index fee5dca1..3e4bead9 100644
--- a/test/buildtool/file_system/file_system_manager.test.cpp
+++ b/test/buildtool/file_system/file_system_manager.test.cpp
@@ -404,3 +404,84 @@ TEST_CASE("FileSystemManager", "[file_system]") {
     CHECK(FileSystemManager::RemoveFile(copy_file));
     CHECK(not FileSystemManager::IsFile(copy_file));
 }
+
+TEST_CASE("CreateFileHardlink", "[file_system]") {
+    std::filesystem::path to{"./tmp-CreateFileHardlink/linked_file"};
+    REQUIRE(FileSystemManager::CreateDirectory(to.parent_path()));
+
+    SECTION("Existing file") {
+        std::filesystem::path from{
+            "test/buildtool/file_system/data/example_file"};
+
+        CHECK(FileSystemManager::CreateFileHardlink(from, to));
+        CHECK(std::filesystem::exists(to));
+
+        CHECK_FALSE(FileSystemManager::CreateFileHardlink(from, to));
+        CHECK(std::filesystem::exists(to));
+
+        CHECK(FileSystemManager::RemoveFile(to));
+        CHECK(not std::filesystem::exists(to));
+    }
+    SECTION("Non-existing file") {
+        std::filesystem::path from{
+            "test/buildtool/file_system/data/this_file_does_not_exist"};
+
+        CHECK_FALSE(FileSystemManager::CreateFileHardlink(from, to));
+        CHECK_FALSE(std::filesystem::exists(to));
+    }
+    SECTION("Existing but not file") {
+        std::filesystem::path from{"./tmp-CreateFileHardlink/dir"};
+        CHECK(FileSystemManager::CreateDirectory(from));
+
+        CHECK_FALSE(FileSystemManager::CreateFileHardlink(from, to));
+        CHECK_FALSE(std::filesystem::exists(to));
+    }
+}
+
+TEST_CASE_METHOD(CopyFileFixture, "CreateFileHardlinkAs", "[file_system]") {
+    auto set_perm = [&](bool is_executable) {
+        auto const content = FileSystemManager::ReadFile(from_);
+        REQUIRE(content);
+        REQUIRE(FileSystemManager::RemoveFile(from_));
+        REQUIRE(FileSystemManager::WriteFileAs(
+            *content,
+            from_,
+            is_executable ? ObjectType::Executable : ObjectType::File));
+    };
+    auto run_test = [&](bool is_executable) {
+        // Hard link creation was successful
+        CHECK(FileSystemManager::CreateFileHardlinkAs(
+            from_,
+            to_,
+            is_executable ? ObjectType::Executable : ObjectType::File));
+
+        // file exists
+        CHECK(std::filesystem::exists(to_));
+        CHECK(std::filesystem::is_regular_file(to_));
+        CHECK(is_executable == FileSystemManager::IsExecutable(to_));
+
+        // permissions should be 0555 or 0444
+        CHECK((is_executable ? HasExecutablePermissions(to_)
+                             : HasFilePermissions(to_)));
+    };
+    SECTION("as file") {
+        SECTION("from file") {
+            set_perm(false);
+            run_test(false);
+        }
+        SECTION("from executable") {
+            set_perm(true);
+            run_test(false);
+        }
+    }
+    SECTION("as executable") {
+        SECTION("from file") {
+            set_perm(false);
+            run_test(true);
+        }
+        SECTION("from executable") {
+            set_perm(true);
+            run_test(true);
+        }
+    }
+}