bugfix: Also unlink symlinks before installing

Make sure that all CopyFile, WriteFile, and CreateSymlink
functions properly unlink the target file (if it exists and
overwrite requested) to avoid interferences of the install
command. With this change, the clean up step for install-cas
and the within GraphTraverser can new be omitted.

3 files changed, 28 insertions, 19 deletions

diff --git a/src/buildtool/file_system/file_system_manager.hpp b/src/buildtool/file_system/file_system_manager.hpp
index 6b6b675f..d905f301 100644
--- a/src/buildtool/file_system/file_system_manager.hpp
+++ b/src/buildtool/file_system/file_system_manager.hpp
@@ -153,6 +153,11 @@ class FileSystemManager {
                             link.parent_path().string());
                 return false;
             }
+            if (not RemoveFile(link)) {
+                Logger::Log(
+                    log_failure_at, "can not remove file {}", link.string());
+                return false;
+            }
 #ifdef __unix__
             std::filesystem::create_directory_symlink(to, link);
             return std::filesystem::is_symlink(link);
@@ -344,7 +349,10 @@ class FileSystemManager {
                                   kSetEpochTime,
                                   kSetWritable>(src, dst, fd_less, opt);
             case ObjectType::Symlink:
-                return CopySymlinkAs<kSetEpochTime>(src, dst);
+                return CopySymlinkAs<kSetEpochTime>(
+                    src,
+                    dst,
+                    opt == std::filesystem::copy_options::overwrite_existing);
             case ObjectType::Tree:
                 break;
         }
@@ -441,7 +449,8 @@ class FileSystemManager {
             if (!std::filesystem::exists(status)) {
                 return true;
             }
-            if (!std::filesystem::is_regular_file(status)) {
+            if (!std::filesystem::is_regular_file(status) and
+                !std::filesystem::is_symlink(status)) {
                 return false;
             }
             return std::filesystem::remove(file);
@@ -1009,6 +1018,11 @@ class FileSystemManager {
                 std::filesystem::is_symlink(dst)) {
                 return false;
             }
+            if (not RemoveFile(dst)) {
+                Logger::Log(
+                    LogLevel::Error, "cannot remove file {}", dst.string());
+                return false;
+            }
             return std::filesystem::copy_file(src, dst, opt);
         } catch (std::exception const& e) {
             Logger::Log(LogLevel::Error,
@@ -1023,6 +1037,11 @@ class FileSystemManager {
     [[nodiscard]] static auto WriteFileImpl(
         std::string const& content,
         std::filesystem::path const& file) noexcept -> bool {
+        if (not FileSystemManager::RemoveFile(file)) {
+            Logger::Log(
+                LogLevel::Error, "can not remove file {}", file.string());
+            return false;
+        }
         try {
             std::ofstream writer{file};
             if (!writer.is_open()) {
@@ -1139,6 +1158,12 @@ class FileSystemManager {
         [[nodiscard]] static auto CopyFile(char const* src,
                                            char const* dst,
                                            bool skip_existing) noexcept -> int {
+            if (not skip_existing) {
+                // remove dst if it exists
+                if (unlink(dst) != 0 and errno != ENOENT) {
+                    return PackError(ERROR_OPEN_OUTPUT, errno);
+                }
+            }
             // NOLINTNEXTLINE(hicpp-signed-bitwise)
             auto write_flags = kWriteFlags | (skip_existing ? O_EXCL : 0);
             auto out = FdOpener{dst, write_flags, kWritePerms};
diff --git a/src/buildtool/graph_traverser/graph_traverser.hpp b/src/buildtool/graph_traverser/graph_traverser.hpp
index df5fa65f..0eee1a80 100644
--- a/src/buildtool/graph_traverser/graph_traverser.hpp
+++ b/src/buildtool/graph_traverser/graph_traverser.hpp
@@ -522,15 +522,7 @@ class GraphTraverser {
         std::vector<std::filesystem::path> output_paths{};
         output_paths.reserve(rel_paths.size());
         for (auto const& rel_path : rel_paths) {
-            auto output_path = clargs_.stage->output_dir / rel_path;
-            if (FileSystemManager::IsFile(output_path) and
-                not FileSystemManager::RemoveFile(output_path)) {
-                Logger::Log(LogLevel::Error,
-                            "Could not clean output path {}",
-                            output_path.string());
-                return std::nullopt;
-            }
-            output_paths.emplace_back(std::move(output_path));
+            output_paths.emplace_back(clargs_.stage->output_dir / rel_path);
         }
         return output_paths;
     }
diff --git a/src/buildtool/main/install_cas.cpp b/src/buildtool/main/install_cas.cpp
index 622e7a1f..b0a2d2f6 100644
--- a/src/buildtool/main/install_cas.cpp
+++ b/src/buildtool/main/install_cas.cpp
@@ -103,14 +103,6 @@ auto FetchAndInstallArtifacts(
                         output_path.parent_path().string());
             return false;
         }
-        if (FileSystemManager::Exists(output_path)) {
-            if (not FileSystemManager::RemoveFile(output_path)) {
-                Logger::Log(LogLevel::Error,
-                            "Failed to remote target location {}.",
-                            output_path.string());
-                return false;
-            }
-        }
         if (not api->RetrieveToPaths(
                 {object_info}, {output_path}, alternative_api)) {
             Logger::Log(LogLevel::Error, "failed to retrieve artifact.");