Make put_file continue on zero-read (#869)

* Make put_file continue on zero-read

* fix test

Author: martindurant

fsspec/spec.py

@@ -803,13 +803,13 @@ def put_file(self, lpath, rpath, callback=_DEFAULT_CALLBACK, **kwargs):
             return None
 
         with open(lpath, "rb") as f1:
-            callback.set_size(f1.seek(0, 2))
+            size = f1.seek(0, 2)
+            callback.set_size(size)
             f1.seek(0)
 
             self.mkdirs(self._parent(os.fspath(rpath)), exist_ok=True)
             with self.open(rpath, "wb", **kwargs) as f2:
-                data = True
-                while data:
+                while f2.tell() < size:
                     data = f1.read(self.blocksize)
                     segment_len = f2.write(data)
                     callback.relative_update(segment_len)

fsspec/tests/test_spec.py

@@ -495,7 +495,9 @@ def test_dummy_callbacks_file(tmpdir):
     source.write_text("x" * 100, "utf-8")
 
     fs.put_file(source, file, callback=callback)
-    assert callback.events == imitate_transfer(size, 10)
+
+    # -1 here since put_file no longer has final zero-size put
+    assert callback.events == imitate_transfer(size, 10)[:-1]
     callback.events.clear()
 
     fs.get_file(file, destination, callback=callback)