feat(arrow): resolve S3-compatible schemes in ArrowFileSystemFileIO

src/iceberg/arrow/arrow_io.cc

@@ -30,6 +30,7 @@
 #include <arrow/io/interfaces.h>
 #include <arrow/result.h>
 #include <arrow/status.h>
+#include <arrow/util/uri.h>
 
 #include "iceberg/arrow/arrow_io_internal.h"
 #include "iceberg/arrow/arrow_io_util.h"
@@ -473,11 +474,26 @@ class ArrowOutputFile : public OutputFile {
 }  // namespace
 
 Result<std::string> ArrowFileSystemFileIO::ResolvePath(const std::string& file_location) {
-  if (file_location.find("://") != std::string::npos) {
-    ICEBERG_ARROW_ASSIGN_OR_RETURN(auto path, arrow_fs_->PathFromUri(file_location));
-    return path;
+  const auto pos = file_location.find("://");
+  if (pos == std::string::npos) {
+    return file_location;
   }
-  return file_location;
+
+  auto path = arrow_fs_->PathFromUri(file_location);
+  if (path.ok()) {
+    return std::move(path).ValueOrDie();
+  }
+
+  // Foreign alias (s3a/s3n): validate via Arrow's parser, then percent-decode the
+  // scheme-less key (substring keeps a Windows drive letter's ':' that host() drops).
+  if (auto parsed = ::arrow::util::Uri::FromString(file_location); !parsed.ok()) {
+    const auto& status = parsed.status();
+    return std::unexpected<Error>{
+        {.kind = ToErrorKind(status), .message = status.ToString()}};
+  }
+  std::string bucket_key = file_location.substr(pos + 3);
+  bucket_key = bucket_key.substr(0, bucket_key.find_first_of("?#"));
+  return ::arrow::util::UriUnescape(bucket_key);
 }
 
 Result<std::shared_ptr<::arrow::io::RandomAccessFile>> OpenArrowInputStream(

src/iceberg/catalog/rest/rest_file_io.cc

@@ -45,7 +45,7 @@ Result<BuiltinFileIOKind> DetectBuiltinFileIO(std::string_view location) {
   if (scheme == "file") {
     return BuiltinFileIOKind::kArrowLocal;
   }
-  if (scheme == "s3") {
+  if (scheme == "s3" || scheme == "s3a" || scheme == "s3n") {
     return BuiltinFileIOKind::kArrowS3;
   }
 

src/iceberg/test/arrow_io_test.cc

@@ -37,6 +37,11 @@ namespace iceberg {
 
 namespace {
 
+std::string ForeignSchemeUri(std::string local_path) {
+  std::ranges::replace(local_path, '\\', '/');
+  return "x-store://" + local_path;
+}
+
 struct CloseState {
   bool closed = false;
 };
@@ -405,6 +410,35 @@ TEST_F(LocalFileIOTest, StdReadKeepsPositionAvailableAtEof) {
   EXPECT_THAT(stream->Position(), HasValue(::testing::Eq(3)));
 }
 
+TEST_F(LocalFileIOTest, ResolvesForeignSchemeToUnderlyingPath) {
+  ASSERT_THAT(file_io_->WriteFile(temp_filepath_, "hello world"), IsOk());
+
+  auto read_res = file_io_->ReadFile(ForeignSchemeUri(temp_filepath_), std::nullopt);
+  EXPECT_THAT(read_res, IsOk());
+  EXPECT_THAT(read_res, HasValue(::testing::Eq("hello world")));
+
+  auto with_query = file_io_->ReadFile(ForeignSchemeUri(temp_filepath_) + "?versionId=42",
+                                       std::nullopt);
+  EXPECT_THAT(with_query, IsOk());
+  EXPECT_THAT(with_query, HasValue(::testing::Eq("hello world")));
+}
+
+TEST_F(LocalFileIOTest, PropagatesNonSchemeMismatchUriError) {
+  auto read_res = file_io_->ReadFile("file:///tmp/%ZZ", std::nullopt);
+  EXPECT_THAT(read_res, IsError(ErrorKind::kUnknownError));
+  EXPECT_THAT(read_res, HasErrorMessage("Cannot parse URI"));
+}
+
+TEST_F(LocalFileIOTest, FallbackDecodesPercentEncodingInKey) {
+  std::string decoded_path = temp_filepath_ + " x";
+  ASSERT_THAT(file_io_->WriteFile(decoded_path, "raw"), IsOk());
+
+  auto read_res =
+      file_io_->ReadFile(ForeignSchemeUri(temp_filepath_ + "%20x"), std::nullopt);
+  EXPECT_THAT(read_res, IsOk());
+  EXPECT_THAT(read_res, HasValue(::testing::Eq("raw")));
+}
+
 TEST(FileIOAdapterTest, InputAdapterRejectsReadsAfterClose) {
   auto state = std::make_shared<PermissiveReadState>();
   state->data = "abc";

src/iceberg/test/rest_file_io_test.cc

@@ -49,6 +49,10 @@ class MockFileIO : public FileIO {
 TEST(RestFileIOTest, DetectBuiltinKindFromScheme) {
   EXPECT_THAT(DetectBuiltinFileIO("s3://bucket/path"),
               HasValue(::testing::Eq(BuiltinFileIOKind::kArrowS3)));
+  EXPECT_THAT(DetectBuiltinFileIO("s3a://bucket/path"),
+              HasValue(::testing::Eq(BuiltinFileIOKind::kArrowS3)));
+  EXPECT_THAT(DetectBuiltinFileIO("s3n://bucket/path"),
+              HasValue(::testing::Eq(BuiltinFileIOKind::kArrowS3)));
   EXPECT_THAT(DetectBuiltinFileIO("/tmp/warehouse"),
               HasValue(::testing::Eq(BuiltinFileIOKind::kArrowLocal)));
   EXPECT_THAT(DetectBuiltinFileIO("file:///tmp/warehouse"),