I think post.add_dependency_uptodate is not used correctly here. It is more or less directly added (for lists, its elements are added) to doit's uptodate field, which expects lists of False, True, None, callables, or strings (which are executed as shell commands) (see http://pydoit.org/dependencies.html#uptodate). I think tools.config_changed should be used here to (somehow) wrap the data added.

Ugh. Ok.

I think doit will try to execute each string as a shell command, and use its return value to determine whether the task changed or not. That's not what you want, I think?

Indeed.

Just out of curiosity, is add_dependency_uptodate used anywhere so I can see how it's done there?

If you want to update if the list of strings changed (maybe you want to sort the list to avoid list reordering triggering rebuilds), use tools.config_changed({1: your_string_list}, 'some unique identifier for the plugin') or so.

I found an example in one of my (not yet published) plugins:

post.add_dependency_uptodate(utils.config_changed({1: some_data}, 'nikola.plugins.path.to.comment.and.its.name:' + post.base_path), False, 'page')

ok, pushing now.

The ID you say "unique"... that means unique in the context of that specific task, right? Not unique across all the tasks?

It should be unique over all posts and tasks, because it could happen that different tasks add something to the uptodate dependency of a post, and many posts are on one index/list/... page, and all those uptodate dependencies are put into the uptodate dependency on the generated index/list/...

I'd use a combination of the task/plugin/... name and the post's source path.

Ugh again then.

This method is completely unusable based on the documentation there. It's a strange feeling to have no idea how this works. I think we should remove the marketing stuff about how nikola's codebase is easy to understand.

Last question: it has to be unique across the whole build and stable from one build to another?

Yes. (Of course, it should be stable iff the options it contains don't change.)
So if you want to force a rebuilt if a list of strings changes (but its order doesn't depend), sort the list, put it into a config_changed object and make its tag depend on the plugin and the post.