auto:upgrade fails when turning "has n" relation to not required

[dlo]

I have a model like the following

class Task
  include DataMapper::Resource

  property :id, Serial
  has n, :things
end

I run automigrate and this table syncs fine. I change it to the following:

class Task
  include DataMapper::Resource

  property :id, Serial
  has n, :things, :required => false
end

And autoupgrade fails on a hard to parse error.

(in /home/me/xyz)
DataMapper::Sweatshop::Unique - ParseTree could not be loaded, anonymous uniques will not be allowed
rake aborted!
Cannot add a NOT NULL column with default value NULL

(See full trace by running task with --trace)

AFAIK I am not changing the column to "NOT NULL". In fact I am changing it to allow null values, not remove them.

Other migration engines (such as South) handle this change pretty gracefully.

[danielribeiro]

+1

[sunomie]

Also fails when trying to add a new has n, :things, :required => false. The new id table is marked as INTEGER NOT NULL despite the required => false. Note that adding a new belongs_to :thing, :required => false works fine. Database I'm currently using is sqlite3.