add support for zst writing (#812)

* add support for zst writing

* windows dammit

* use our special named_temporary_file decorator

smart_open/compression.py

@@ -106,8 +106,8 @@ def _handle_gzip(file_obj, mode):
 
 
 def _handle_zstd(file_obj, mode):
-    import zstandard as zstd
-    result = zstd.ZstdDecompressor().stream_reader(file_obj, closefd=True)
+    import zstandard  # type: ignore
+    result = zstandard.open(filename=file_obj, mode=mode)
     return result
 
 

smart_open/tests/test_smart_open.py

@@ -77,6 +77,18 @@ def named_temporary_file(mode='w+b', prefix=None, suffix=None, delete=True):
             logger.error(e)
 
 
+def test_zst_write():
+    with named_temporary_file(suffix=".zst") as tmp:
+        with smart_open.open(tmp.name, "wt") as fout:
+            print("hello world", file=fout)
+            print("this is a test", file=fout)
+
+        with smart_open.open(tmp.name, "rt") as fin:
+            got = list(fin)
+
+    assert got == ["hello world\n", "this is a test\n"]
+
+
 class ParseUriTest(unittest.TestCase):
     """
     Test ParseUri class.