class RuboCop::Cop::Rails::UniqBeforePluck
Prefer the use of uniq (or distinct), before pluck instead of after.
The use of uniq before pluck is preferred because it executes within the database.
This cop has two different enforcement modes. When the EnforcedStyle is conservative (the default) then only calls to pluck on a constant (i.e. a model class) before uniq are added as offenses.
When the EnforcedStyle is aggressive then all calls to pluck before uniq are added as offenses. This may lead to false positives as the cop cannot distinguish between calls to pluck on an ActiveRecord::Relation vs a call to pluck on an ActiveRecord::Associations::CollectionProxy.
Autocorrect is disabled by default for this cop since it may generate false positives.
@example EnforcedStyle: conservative (default)
# bad Model.pluck(:id).uniq # good Model.uniq.pluck(:id)
@example EnforcedStyle: aggressive
# bad # this will return a Relation that pluck is called on Model.where(cond: true).pluck(:id).uniq # bad # an association on an instance will return a CollectionProxy instance.assoc.pluck(:id).uniq # bad Model.pluck(:id).uniq # good Model.uniq.pluck(:id)
Constants
- MSG
- NEWLINE
- PATTERN
Public Instance Methods
# File lib/rubocop/cop/rails/uniq_before_pluck.rb, line 73 def autocorrect(node) lambda do |corrector| method = node.method_name corrector.remove(dot_method_with_whitespace(method, node)) corrector.insert_before(node.receiver.loc.dot.begin, ".#{method}") end end
# File lib/rubocop/cop/rails/uniq_before_pluck.rb, line 60 def on_send(node) method = if style == :conservative conservative_node_match(node) else aggressive_node_match(node) end return unless method add_offense(node, location: :selector, message: format(MSG, method: method)) end
Private Instance Methods
# File lib/rubocop/cop/rails/uniq_before_pluck.rb, line 93 def dot_method_begin_pos(method, node) lines = node.source.split(NEWLINE) if lines.last.strip == ".#{method}" node.source.rindex(NEWLINE) else node.loc.dot.begin_pos end end
# File lib/rubocop/cop/rails/uniq_before_pluck.rb, line 88 def dot_method_with_whitespace(method, node) range_between(dot_method_begin_pos(method, node), node.loc.selector.end_pos) end
# File lib/rubocop/cop/rails/uniq_before_pluck.rb, line 84 def style_parameter_name 'EnforcedStyle' end