resolve a couple of review comments; enum workaround

cpp/cmake_modules/ThirdpartyToolchain.cmake

@@ -2537,6 +2537,10 @@ if(ARROW_S3)
   message(STATUS "Found AWS SDK libraries: ${AWSSDK_LINK_LIBRARIES}")
 
   if(APPLE)
+    # CoreFoundation's path is hardcoded in the CMake files provided by
+    # aws-sdk-cpp to use the MacOSX SDK provided by XCode which makes
+    # XCode a hard dependency. Command Line Tools is often used instead
+    # of the full XCode suite, so let the linker to find it.
     set_target_properties(AWS::aws-c-common
                           PROPERTIES INTERFACE_LINK_LIBRARIES
                                      "-pthread;pthread;-framework CoreFoundation")

python/pyarrow/_fs.pyx

@@ -371,7 +371,6 @@ cdef class FileSystem:
 
         stream.set_input_stream(in_handle)
         stream.is_readable = True
-        stream.is_seekable = True
 
         return self._wrap_input_stream(
             stream, path=path, compression=compression, buffer_size=buffer_size

python/pyarrow/_s3.pyx

@@ -19,12 +19,12 @@
 
 import six
 
+from pyarrow.lib cimport check_status
 from pyarrow.compat import frombytes, tobytes
 from pyarrow.includes.common cimport *
 from pyarrow.includes.libarrow cimport *
 from pyarrow.includes.libarrow_s3 cimport *
 from pyarrow._fs cimport FileSystem
-from pyarrow.lib cimport check_status
 
 
 cpdef enum S3LogLevel:

python/pyarrow/includes/libarrow.pxd

@@ -964,7 +964,7 @@ cdef extern from "arrow/io/api.h" namespace "arrow::io" nogil:
 
 cdef extern from "arrow/filesystem/api.h" namespace "arrow::fs" nogil:
 
-    enum CFileType "arrow::fs::FileType":
+    ctypedef enum CFileType "arrow::fs::FileType":
         CFileType_NonExistent "arrow::fs::FileType::NonExistent"
         CFileType_Unknown "arrow::fs::FileType::Unknown"
         CFileType_File "arrow::fs::FileType::File"

python/pyarrow/includes/libarrow_s3.pxd

@@ -24,7 +24,7 @@ from pyarrow.includes.libarrow cimport CFileSystem
 
 cdef extern from "arrow/filesystem/api.h" namespace "arrow::fs" nogil:
 
-    enum CS3LogLevel "arrow::fs::S3LogLevel":
+    ctypedef enum CS3LogLevel "arrow::fs::S3LogLevel":
         CS3LogLevel_Off "arrow::fs::S3LogLevel::Off"
         CS3LogLevel_Fatal "arrow::fs::S3LogLevel::Fatal"
         CS3LogLevel_Error "arrow::fs::S3LogLevel::Error"