With Drupal 8.4.x as of 9 Mar 2017, if you try to migrate a multilingual Drupal 6 site using CCK and several i18n/translation modules, you will run into some problems. [earlier 8.x versions -- there were more problems -- see original summary section below].
The main difficulty remaining is taxonomy. If you are using i18ntaxonomy to translate taxonomy terms:
- The taxonomy translations will not come through
- Node translations in foreign languages tagged with the taxonomy will not come through tagged at all
I also had a problem with one of the vocabularies, that the vocabulary, terms, and nodes came through, and the nodes have the tags on them, but when you go to the tag page, the node isn't listed.
There were also several other problems with the migration; see comment #14 for details... issues will be filed.
User interface changes
Migration will work better.
Data model changes
Original report (outdated)
I recently tried out the experimental Migrate, Migrate Drupal, and Migrate UI modules for the first time, on an existing Drupal 6 site (I know, it should have been done long ago. But.).
I ran into a problem where in some nodes having multiple revisions, the latest revision was imported with an empty Body field. The older revisions of the same nodes are fine.
I looked in the database, and the node_revision__body table is missing an entry for the latest revision (it has entries for the earlier revisions), and the node__body has no entry at all for that node ID.
There were some errors in the migrate log, which looked like this:
Source ID 951: Unable to get entity
(with no other information, but they occurred during the time when the import was getting node revisions). However, there was not a message that matched the node ID or revision ID of one of the nodes I saw this problem on. There were quite a few with this problem, but not all nodes with revisions had the problem.
I have no idea how to debug this or what other information I can provide... but it happened. It may be limited to one content type, which happened to have the machine name "article" on my old site -- at least, I have only seen it on Article content so far, but I haven't looked through the other content yet. I deleted the Standard install profile's Article and Page content types before I did the migration. Page content seems to have come through without any problem. ???