fix windows linking error

Signed-off-by: Junwang Zhao <zhjwpku@gmail.com>

Author: zhjwpku

src/iceberg/arrow/arrow_error_transform_internal.h

@@ -39,8 +39,8 @@ inline ErrorKind ToErrorKind(const ::arrow::Status& status) {
 #define ICEBERG_INTERNAL_ASSIGN_OR_RETURN_IMPL(result_name, lhs, rexpr, error_transform) \
   auto&& result_name = (rexpr);                                                          \
   if (!result_name.ok()) {                                                               \
-    return unexpected(                                                                   \
-        Error(error_transform(result_name.status()), result_name.status().ToString()));  \
+    return unexpected<Error>{{.kind = error_transform(result_name.status()),             \
+                              .message = result_name.status().ToString()}};              \
   }                                                                                      \
   lhs = std::move(result_name).ValueOrDie();
 
@@ -53,7 +53,8 @@ inline ErrorKind ToErrorKind(const ::arrow::Status& status) {
   do {                                                                              \
     auto&& _status = (expr);                                                        \
     if (!_status.ok()) {                                                            \
-      return unexpected(Error(internal::ToErrorKind(_status), _status.ToString())); \
+      return unexpected<Error>{                                                     \
+          {.kind = internal::ToErrorKind(_status), .message = _status.ToString()}}; \
     }                                                                               \
   } while (0)
 

src/iceberg/arrow/io/local_file_io.cc

@@ -50,7 +50,8 @@ expected<std::string, Error> LocalFileIO::ReadFile(const std::string& file_locat
 expected<void, Error> LocalFileIO::WriteFile(const std::string& file_location,
                                              std::string_view content, bool overwrite) {
   if (!overwrite && FileExists(file_location)) {
-    return unexpected(Error(ErrorKind::kAlreadyExists, ""));
+    return unexpected(
+        Error(ErrorKind::kAlreadyExists, std::format("File {} exists", file_location)));
   }
   ICEBERG_INTERNAL_ASSIGN_OR_RETURN(auto file,
                                     local_fs_->OpenOutputStream(file_location));

src/iceberg/demo.cc

@@ -21,6 +21,7 @@
 
 #include "iceberg/avro.h"  // include to export symbols
 #include "iceberg/catalog.h"
+#include "iceberg/file_io.h"
 #include "iceberg/location_provider.h"
 #include "iceberg/table.h"
 #include "iceberg/transaction.h"

src/iceberg/error.h

@@ -35,16 +35,14 @@ enum class ErrorKind {
   kCommitStateUnknown,
   kInvalidArgument,
   kIOError,
+  kNotImplemented,
   kUnknownError,
 };
 
 /// \brief Error with a kind and a message.
 struct ICEBERG_EXPORT [[nodiscard]] Error {
   ErrorKind kind;
   std::string message;
-
-  explicit Error(ErrorKind kind, std::string message)
-      : kind(kind), message(std::move(message)) {};
 };
 
 }  // namespace iceberg

src/iceberg/file_io.h

@@ -47,7 +47,13 @@ class ICEBERG_EXPORT FileIO {
   /// \return The content of the file if the read succeeded, an error code if the read
   /// failed.
   virtual expected<std::string, Error> ReadFile(const std::string& file_location,
-                                                std::optional<size_t> length) = 0;
+                                                std::optional<size_t> length) {
+    // The following line is to avoid Windows linker error LNK2019.
+    // If this function is defined as pure virtual function, the `unexpected<Error>` will
+    // not be instantiated and exported in libiceberg.
+    return unexpected<Error>{
+        {.kind = ErrorKind::kNotImplemented, .message = "ReadFile not implemented"}};
+  }
 
   /// \brief Write the given content to the file at the given location.
   ///
@@ -57,7 +63,13 @@ class ICEBERG_EXPORT FileIO {
   /// file exists.
   /// \return void if the write succeeded, an error code if the write failed.
   virtual expected<void, Error> WriteFile(const std::string& file_location,
-                                          std::string_view content, bool overwrite) = 0;
+                                          std::string_view content, bool overwrite) {
+    // The following line is to avoid Windows linker error LNK2019.
+    // If this function is defined as pure virtual function, the `unexpected<Error>` will
+    // not be instantiated and exported in libiceberg.
+    return unexpected<Error>{
+        {.kind = ErrorKind::kNotImplemented, .message = "WriteFile not implemented"}};
+  }
 
   /// \brief Delete a file at the given location.
   ///

test/local_file_io_test.cc

@@ -35,7 +35,7 @@ class LocalFileIOTest : public testing::Test {
   std::filesystem::path tmpfile = std::filesystem::temp_directory_path() / "123.txt";
 };
 
-TEST_F(LocalFileIOTest, readWriteFile) {
+TEST_F(LocalFileIOTest, ReadWriteFile) {
   auto read_res = file_io_->ReadFile(tmpfile.string(), 1024);
   EXPECT_EQ(read_res.error().kind, iceberg::ErrorKind::kInvalidArgument);
 
@@ -49,7 +49,7 @@ TEST_F(LocalFileIOTest, readWriteFile) {
   EXPECT_EQ(read_res.value(), "hello world");
 }
 
-TEST_F(LocalFileIOTest, deleteFile) {
+TEST_F(LocalFileIOTest, DeleteFile) {
   auto del_res = file_io_->DeleteFile(tmpfile.string());
   EXPECT_TRUE(del_res.has_value());