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Class: RuboCop::Cop::Style::TrailingCommaInBlockArgs

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::RuboCop::Cop::AutoCorrector, ::RuboCop::Cop::Base, ::RuboCop::ExcludeLimit, NodePattern::Macros, RuboCop::AST::Sexp
Instance Chain:
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/style/trailing_comma_in_block_args.rb

Overview

Checks whether trailing commas in block arguments are required. Blocks with only one argument and a trailing comma require that comma to be present. Blocks with more than one argument never require a trailing comma.

Examples:

# bad
add { |foo, bar,| foo + bar }

# good
add { |foo, bar| foo + bar }

# good
add { |foo,| foo }

# good
add { foo }

# bad
add do |foo, bar,|
  foo + bar
end

# good
add do |foo, bar|
  foo + bar
end

# good
add do |foo,|
  foo
end

# good
add do
  foo + bar
end

Cop Safety Information:

  • This cop is unsafe because a trailing comma can indicate there are more parameters that are not used.

    For example:

    # with a trailing comma
    {foo: 1, bar: 2, baz: 3}.map {|key,| key }
    #=> [:foo, :bar, :baz]
    
    # without a trailing comma
    {foo: 1, bar: 2, baz: 3}.map {|key| key }
    #=> [[:foo, 1], [:bar, 2], [:baz, 3]]

    This can be fixed by replacing the trailing comma with a placeholder argument (such as |key, _value|).

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

::RuboCop::Cop::Base - Inherited

.gem_requirements, .lint?,
.support_autocorrect?

Returns if class supports autocorrect.

.support_multiple_source?

Override if your cop should be called repeatedly for multiple investigations Between calls to on_new_investigation and on_investigation_end, the result of processed_source will remain constant.

Class Method Summary

::RuboCop::Cop::Base - Inherited

.autocorrect_incompatible_with

List of cops that should not try to autocorrect at the same time as this cop.

.badge

Naming.

.callbacks_needed, .cop_name, .department,
.documentation_url

Returns an url to view this cops documentation online.

.exclude_from_registry

Call for abstract Cop classes.

.inherited,
.joining_forces

Override and return the Force class(es) you need to join.

.match?

Returns true if the cop name or the cop namespace matches any of the given names.

.new,
.requires_gem

Register a version requirement for the given gem name.

.restrict_on_send

::RuboCop::ExcludeLimit - Extended

exclude_limit

Sets up a configuration option to have an exclude limit tracked.

transform

Instance Attribute Summary

Instance Method Summary

::RuboCop::Cop::Base - Inherited

#add_global_offense

Adds an offense that has no particular location.

#add_offense

Adds an offense on the specified range (or node with an expression) Unless that offense is disabled for this range, a corrector will be yielded to provide the cop the opportunity to autocorrect the offense.

#begin_investigation

Called before any investigation.

#callbacks_needed,
#cop_config

Configuration Helpers.

#cop_name, #excluded_file?,
#external_dependency_checksum

This method should be overridden when a cop’s behavior depends on state that lives outside of these locations:

#inspect
#message

Gets called if no message is specified when calling add_offense or add_global_offense Cops are discouraged to override this; instead pass your message directly.

#name

Alias for Base#cop_name.

#offenses,
#on_investigation_end

Called after all on_…​

#on_new_investigation

Called before all on_…​

#on_other_file

Called instead of all on_…​

#parse

There should be very limited reasons for a Cop to do it’s own parsing.

#parser_engine,
#ready

Called between investigations.

#relevant_file?, #target_rails_version, #target_ruby_version, #annotate, #apply_correction, #attempt_correction,
#callback_argument

Reserved for Cop::Cop.

#complete_investigation

Called to complete an investigation.

#correct, #current_corrector,
#current_offense_locations

Reserved for Commissioner:

#current_offenses, #currently_disabled_lines, #custom_severity, #default_severity, #disable_uncorrectable, #enabled_line?, #file_name_matches_any?, #find_message, #find_severity, #range_for_original, #range_from_node_or_range,
#reset_investigation

Actually private methods.

#use_corrector

::RuboCop::Cop::AutocorrectLogic - Included

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

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

Instance Method Details

#arg_count(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_comma_in_block_args.rb', line 83

def arg_count(node)
  node.arguments.each_descendant(:arg, :optarg, :kwoptarg).to_a.size
end

#argument_tokens(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_comma_in_block_args.rb', line 95

def argument_tokens(node)
  tokens = processed_source.tokens_within(node)
  pipes = tokens.select { |token| token.type == :tPIPE }
  begin_pos, end_pos = pipes.map { |pipe| tokens.index(pipe) }

  tokens[begin_pos + 1..end_pos - 1]
end

#last_comma(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_comma_in_block_args.rb', line 91

def last_comma(node)
  argument_tokens(node).last
end

#on_block(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_comma_in_block_args.rb', line 67

def on_block(node) # rubocop:disable InternalAffairs/NumblockHandler
  # lambda literal (`->`) never has block arguments.
  return if node.send_node.lambda_literal?
  return unless useless_trailing_comma?(node)

  last_comma_pos = last_comma(node).pos

  add_offense(last_comma_pos) { |corrector| corrector.replace(last_comma_pos, '') }
end

#trailing_comma?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_comma_in_block_args.rb', line 87

def trailing_comma?(node)
  argument_tokens(node).last.comma?
end

#useless_trailing_comma?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/trailing_comma_in_block_args.rb', line 79

def useless_trailing_comma?(node)
  arg_count(node) > 1 && trailing_comma?(node)
end