Wrong geometry type for buildings in geojson

[jacksteel@…]

What steps will reproduce the problem?

I have a file created in version 11427 ('Old Version' from here on) of JOSM. These files contain some mapped buildings, which when saved to GeoJson are given the geometry type 'Polygon'.

However, when this file is opened in the latest version of JOSM and saved as GeoJson some of the buildings are given the geometry type 'Polygon' but some are given the geometry type 'LineString' with no obvious pattern as to which get the correct 'Polygon' geometry.

What is the expected result?

All features that output as geometry type 'Polygon' in the Old version should output as 'Polygon' in the latest version

What happens instead?

Some are given the geometry type 'Linestring'

Please provide any additional information below. Attach a screenshot if possible.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2018-03-26 22:16:39 +0200 (Mon, 26 Mar 2018)
Build-Date:2018-03-26 20:45:23
Revision:13576
Redirecting:to URL 'https://josm.openstreetmap.de/svn/trunk':
Relative:URL: ^/trunk

Identification: JOSM/1.5 (13576 en_GB) Windows 10 64-Bit
OS Build number: Windows 10 Enterprise 1709 (16299)
Memory Usage: 222 MB / 989 MB (96 MB allocated, but free)
Java version: 1.8.0_161-b12, Oracle Corporation, Java HotSpot(TM) Client VM
Screen: \Display0 2560x1440
Maximum Screen Size: 2560x1440
Dataset consistency test: No problems found

Plugins:
+ imagery_offset_db (34109)
+ turnrestrictions (34129)

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.
- W: Region [TMS_BLOCK_v2] Resetting cache

[jacksteel@…]

Original file from old version, all buildings should output as polygons

[Don-vip]

Did you take a look to your data? You have a lot of unclosed building. If you run the validator you get 73 errors and 589 warnings... Please clean your dataset before exporting to GeoJson.