Deprecate write_bytes option in Unpacker. (#262)

Fixes #197

Author: methane

msgpack/_unpacker.pyx

@@ -458,6 +458,9 @@ cdef class Unpacker(object):
         cdef object obj
         cdef Py_ssize_t prev_head
 
+        if write_bytes is not None:
+            PyErr_WarnEx(DeprecationWarning, "`write_bytes` option is deprecated. Use `.tell()` instead.", 1)
+
         if self.buf_head >= self.buf_tail and self.file_like is not None:
             self.read_from_file()
 

msgpack/fallback.py

@@ -609,26 +609,30 @@ def __next__(self):
     def skip(self, write_bytes=None):
         self._unpack(EX_SKIP)
         if write_bytes is not None:
+            warnings.warn("`write_bytes` option is deprecated.  Use `.tell()` instead.", DeprecationWarning)
             write_bytes(self._buffer[self._buf_checkpoint:self._buff_i])
         self._consume()
 
     def unpack(self, write_bytes=None):
         ret = self._unpack(EX_CONSTRUCT)
         if write_bytes is not None:
+            warnings.warn("`write_bytes` option is deprecated.  Use `.tell()` instead.", DeprecationWarning)
             write_bytes(self._buffer[self._buf_checkpoint:self._buff_i])
         self._consume()
         return ret
 
     def read_array_header(self, write_bytes=None):
         ret = self._unpack(EX_READ_ARRAY_HEADER)
         if write_bytes is not None:
+            warnings.warn("`write_bytes` option is deprecated.  Use `.tell()` instead.", DeprecationWarning)
             write_bytes(self._buffer[self._buf_checkpoint:self._buff_i])
         self._consume()
         return ret
 
     def read_map_header(self, write_bytes=None):
         ret = self._unpack(EX_READ_MAP_HEADER)
         if write_bytes is not None:
+            warnings.warn("`write_bytes` option is deprecated.  Use `.tell()` instead.", DeprecationWarning)
             write_bytes(self._buffer[self._buf_checkpoint:self._buff_i])
         self._consume()
         return ret