Class: RuboCop::Cop::Gusto::PluckOnSelect

Inherits:
Base
  • Object
show all
Defined in:
lib/rubocop/cop/gusto/pluck_on_select.rb

Overview

Do not use ‘.pluck` on `.select`.

‘.select` returns an ActiveRecord relation with only the selected columns marked for retrieval. `.pluck` returns an array of column values. When chained, `.pluck` is unaware of any directive passed to `.select` (e.g. column aliases or a DISTINCT clause), which can cause unexpected behavior.

Examples:

Redundant select

# bad
User.select(:id).pluck(:id)

# good
User.pluck(:id)

Column alias: .pluck raises “Unknown column” because it ignores the alias

# bad
User.select('id AS id2').pluck('id2')

# good: use .select alone if you need the alias
User.select(:id, 'id AS id2')

# good: use .pluck alone if you don't need the alias
User.pluck(:id)

DISTINCT: .pluck loads all rows, ignoring the DISTINCT from .select

# bad
User.select('DISTINCT email').pluck(:email)

# good
User.distinct.pluck(:email)

Constant Summary collapse

RESTRICT_ON_SEND = 
%i(pluck).freeze
MSG = 
"Do not use `.pluck` on `.select`."

Instance Method Summary collapse

Instance Method Details

#on_send(node) ⇒ Object Also known as: on_csend 



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# File 'lib/rubocop/cop/gusto/pluck_on_select.rb', line 41

def on_send(node)
  return unless node.receiver

  receiver_node = node.receiver
  while receiver_node
    if receiver_node.call_type? && receiver_node.method?(:select)
      add_offense(node)
      break
    end
    receiver_node = receiver_node.receiver
  end
end