Class: RuboCop::Cop::Rails::UniqBeforePluck

Inherits:
Cop
  • Object
show all
Defined in:
lib/rubocop/cop/rails/uniq_before_pluck.rb

Overview

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 EnforcedMode 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 EnforcedMode 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.

Examples:

# bad
Model.pluck(:id).uniq

# good
Model.uniq.pluck(:id)
# this will return a Relation that pluck is called on
Model.where(...).pluck(:id).uniq

# an association on an instance will return a CollectionProxy
instance.assoc.pluck(:id).uniq

Constant Summary collapse

MSG = 
'Use `%s` before `pluck`'.freeze
NEWLINE = 
"\n".freeze
PATTERN = 
'[!^block (send (send %s :pluck ...) ${:uniq :distinct} ...)]'
.freeze

Constants included from Util

Util::ASGN_NODES, Util::BYTE_ORDER_MARK, Util::EQUALS_ASGN_NODES, Util::LITERAL_REGEX, Util::OPERATOR_METHODS, Util::SHORTHAND_ASGN_NODES

Instance Attribute Summary

Attributes inherited from Cop

#config, #corrections, #offenses, #processed_source

Instance Method Summary collapse

Methods inherited from Cop

#add_offense, all, #config_to_allow_offenses, #config_to_allow_offenses=, #cop_config, #cop_name, cop_name, cop_type, #correct, #debug?, #details, #display_cop_names?, #display_style_guide?, #excluded_file?, #extra_details?, #highlights, inherited, #initialize, #join_force?, lint?, match?, #message, #messages, non_rails, #parse, qualified_cop_name, #reference_url, #relevant_file?, #style_guide_url, #target_ruby_version

Methods included from Sexp

#s

Methods included from NodePattern::Macros

#def_node_matcher, #def_node_search, #node_search_body

Methods included from AutocorrectLogic

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #support_autocorrect?

Methods included from IgnoredNode

#ignore_node, #ignored_node?, #part_of_ignored_node?

Methods included from Util

begins_its_line?, block_length, comment_line?, directions, double_quotes_acceptable?, double_quotes_required?, effective_column, ends_its_line?, escape_string, first_part_of_call_chain, interpret_string_escapes, line_range, move_pos, needs_escaping?, numeric_range_size, on_node, operator?, parentheses?, parenthesized_call?, range_with_surrounding_comma, range_with_surrounding_space, source_range, strip_quotes, to_string_literal, to_symbol_literal, within_node?

Methods included from PathUtil

absolute?, match_path?, relative_path

Constructor Details

This class inherits a constructor from RuboCop::Cop::Cop

Instance Method Details

#autocorrect(node) ⇒ Object 



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# File 'lib/rubocop/cop/rails/uniq_before_pluck.rb', line 60

def autocorrect(node)
  send_pluck, method, *_args = *node
  lambda do |corrector|
    corrector.remove(dot_method_with_whitespace(method, node))
    corrector.insert_before(send_pluck.loc.dot.begin, ".#{method}")
  end
end

#on_send(node) ⇒ Object 



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# File 'lib/rubocop/cop/rails/uniq_before_pluck.rb', line 50

def on_send(node)
  method = if mode == :conservative
             conservative_node_match(node)
           else
             aggressive_node_match(node)
           end

  add_offense(node, :selector, format(MSG, method)) if method
end