dm-many-to-many weirdness

gistfile1.rb

class Calendar
    include DataMapper::Resource
    has n, :events
    property :id, Serial
    property :slug, Slug
    property :title, String
    property :published, Boolean
    property :created_at, DateTime
end

class Constraint
    include DataMapper::Resource
    has n, :events, :through => Resource
    property :id, Serial
    property :name, String
    property :slug, String
end

class Event
    include DataMapper::Resource
    property :id, Serial
    property :title, String
    property :occurs_at, DateTime

    belongs_to :calendar
    has n, :constraints, :through => Resource
end

DataMapper.finalize.auto_migrate!
  
events = Event.all(Event.constraints.slug => params[:constraint_slug] )

# results in
# DataMapper::UnknownRelationshipError: No relationships named event or event in ConstraintEvent

# If one then tries

constraints = Constraint.all(Constraint.events.title => 'something')

# then the error is different (the generated SQL does not include the joins)
# Basically, the first query to be called will fail, the second will fail with a different error, then the first will work!