Turn on mpyp checks for filesystem (#14425)

abergmeier · web-flow · commit b5a8b543724e · 2021-04-08T11:46:00.000-07:00
* Turn on mpyp checks for filesystem

- Needs some explicit asserts
- Use BinaryIO.closed as property

* Appease formatting
diff --git a/sdks/python/apache_beam/io/filesystem.py b/sdks/python/apache_beam/io/filesystem.py
@@ -202,9 +202,7 @@ def write(self, data):
     if compressed:
       self._file.write(compressed)
 
-  def _fetch_to_internal_buffer(self, num_bytes):
-    # type: (int) -> None
-
+  def _fetch_to_internal_buffer(self, num_bytes: int) -> None:
     """Fetch up to num_bytes into the internal buffer."""
     if (not self._read_eof and self._read_position > 0 and
         (self._read_buffer.tell() - self._read_position) < num_bytes):
@@ -216,6 +214,7 @@ def _fetch_to_internal_buffer(self, num_bytes):
       self._clear_read_buffer()
       self._read_buffer.write(data)
 
+    assert self._decompressor
     while not self._read_eof and (self._read_buffer.tell() -
                                   self._read_position) < num_bytes:
       # Continue reading from the underlying file object until enough bytes are
@@ -289,23 +288,22 @@ def readline(self):
 
     return bytes_io.getvalue()
 
-  def closed(self):
-    # type: () -> bool
-    return not self._file or self._file.closed()
+  def closed(self) -> bool:
+    return not self._file or self._file.closed
 
-  def close(self):
-    # type: () -> None
+  def close(self) -> None:
     if self.readable():
       self._read_buffer.close()
 
     if self.writeable():
+      assert self._compressor
       self._file.write(self._compressor.flush())
 
     self._file.close()
 
-  def flush(self):
-    # type: () -> None
+  def flush(self) -> None:
     if self.writeable():
+      assert self._compressor
       self._file.write(self._compressor.flush())
     self._file.flush()
 
diff --git a/sdks/python/mypy.ini b/sdks/python/mypy.ini
@@ -65,6 +65,9 @@ ignore_errors = true
 [mypy-apache_beam.io.*]
 ignore_errors = true
 
+[mypy-apache_beam.io.filesystem]
+ignore_errors = false
+
 [mypy-apache_beam.io.iobase]
 ignore_errors = false
 
