Operating system: Ubuntu
Broken: (example: 2.80, master, 2019-03-22
I'm attaching a blend file with a 2 lines script.
When you try to unhide collections in the viewport with:
for coll in bpy.context.scene.collection.children:
coll.hide_viewport = False
This seems not to work with collections that have been hidden manually by pressing the "eye" icon in the outliner. Those manually hidden collections don't unhide with this command, whereas a collection that has been hidden with "coll.hide_viewport = True" does unhide with the False command.