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Class: RuboCop::Cop::Style::StringConcatenation

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:
self, ::RuboCop::Cop::Base, ::RuboCop::Cop::AutocorrectLogic, ::RuboCop::Cop::IgnoredNode, ::RuboCop::Util, RuboCop::AST::Sexp
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/style/string_concatenation.rb

Overview

Checks for places where string concatenation can be replaced with string interpolation.

The cop can autocorrect simple cases but will skip autocorrecting more complex cases where the resulting code would be harder to read. In those cases, it might be useful to extract statements to local variables or methods which you can then interpolate in a string.

Note
 When concatenation between two strings is broken over multiple lines, this cop does not register an offense; instead, Style/LineEndConcatenation will pick up the offense if enabled.

This cop does not register an offense for concatenation with a heredoc either, because interpolating the heredoc into a string literal would not make the code easier to read.

Two modes are supported: 1. aggressive style checks and corrects all occurrences of {} where either the left or right side of {} is a string literal. 2. conservative style on the other hand, checks and corrects only if left side (receiver of + method call) is a string literal. This is useful when the receiver is some expression that returns string like Pathname instead of a string literal.

Examples:

Mode: aggressive (default)

# bad
email_with_name = user.name + ' <' + user.email + '>'
Pathname.new('/') + 'test'

# good
email_with_name = "#{user.name} <#{user.email}>"
email_with_name = format('%s <%s>', user.name, user.email)
"#{Pathname.new('/')}test"

# accepted, line-end concatenation
name = 'First' +
  'Last'

# accepted, concatenation with a heredoc
'Hello' + <<~TEXT
  world
TEXT

Mode: conservative

# bad
'Hello' + user.name

# good
"Hello #{user.name}"
user.name + '!!'
Pathname.new('/') + 'test'

Cop Safety Information:

  • This cop is unsafe in aggressive mode, as it cannot be guaranteed that the receiver is actually a string, which can result in a false positive.

Constant Summary

::RuboCop::Cop::Base - Inherited

DEPARTMENT_SEVERITIES, EMPTY_OFFENSES, RESTRICT_ON_SEND

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

support_autocorrect?

::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 a 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

Reserved for Commissioner.

::RuboCop::ExcludeLimit - Extended

exclude_limit

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

Instance Attribute Summary

::RuboCop::Cop::Base - Inherited

#active_support_extensions_enabled?, #always_autocorrect?, #config, #config_to_allow_offenses, #config_to_allow_offenses=, #contextual_autocorrect?, #disabled_autocorrect?,
#preview?

Whether the user opted in to unstable behavior, with --preview or AllCops: Preview.
#processed_source, #project_index, #string_literals_frozen_by_default?, #target_satisfies_all_gem_version_requirements?

::RuboCop::Cop::AutocorrectLogic - Included

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #autocorrect_with_disable_uncorrectable?, #correctable?, #disable_uncorrectable?, #safe_autocorrect?,
#skipped_unsafe_correction_with_disable_uncorrectable?

Whether a correction exists but is skipped because it is unsafe in a safe autocorrect run, while --disable-uncorrectable asks for a todo comment on everything this run cannot correct.
#contextual_autocorrect_held_back?

When LSP is enabled or the --editor-mode option is on, it is considered as editing source code, and autocorrection with AutoCorrect: contextual will not be performed.

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

 — grouped under the Commissioner heading above.
#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_gem_version

Returns the version of a gem in the target, by default its locked version (i.e. from Gemfile.lock or gems.locked).
#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, #covering_disabled_range, #current_corrector,
#current_offense_locations

Reserved for Commissioner:
#current_offenses, #currently_disabled_lines, #custom_severity, #default_severity, #disable_uncorrectable, #enabled_line?,
#enabled_lines?

A multi-line offense is suppressed by a directive on any line of its range, not only its first line, matching the intuition that the directive is attached to the offending code.
#file_name_matches_any?, #find_message, #find_severity, #matches_absolute_include_pattern?, #new_offense, #range_for_original, #range_from_node_or_range,
#reset_investigation

Actually private methods.
#suppression_reason

The -- reason on the directive that suppresses offenses on this range, or nil when the directive carries none.
#use_corrector

::RuboCop::Cop::AutocorrectLogic - Included

#disable_offense, #disable_offense_at_end_of_line, #disable_offense_before_and_after, #disable_offense_with_eol_or_surround_comment, #eol_comment, #eol_comment_would_be_inside_literal?, #heredoc_range, #line_with_eol_comment_too_long?, #max_line_length, #multiline_ranges, #multiline_string?,
#range_by_lines

Expand the given range to include all of any lines it covers.
#range_of_first_line, #string_continuation?, #surrounding_heredoc?, #surrounding_percent_array?

::RuboCop::Cop::IgnoredNode - Included

#ignore_node, #ignored_node?, #part_of_ignored_node?, #ignored_nodes

Constructor Details

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

Instance Method Details

#adjust_str(part) (private)

[ GitHub ] 

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 169



def adjust_str(part)
  case part.type
  when :str
    adjust_str_literal(part)
  when :dstr, :begin
    part.children.map do |child|
      adjust_str(child)
    end.join
  else
    "\#{#{part.source}}"
  end
end


  








  

    #adjust_str_literal(part)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 182



def adjust_str_literal(part)
  if file_keyword?(part)
    "\#{#{part.source}}"
  elsif single_quoted?(part)
    part.value.gsub(/(\\|"|#\{|#@|#\$)/, '\\\\\&')
  elsif double_quoted?(part)
    # Reuse the source as written - rebuilding it from the value via
    # `inspect` would rewrite the author's escape notation
    # (e.g. `\x0a` into `\n`).
    part.source[1..-2]
  else
    part.value.inspect[1..-2]
  end
end


  








  

    #collect_parts(node, parts = [])   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 129



def collect_parts(node, parts = [])
  return unless node

  if plus_node?(node)
    collect_parts(node.receiver, parts)
    collect_parts(node.first_argument, parts)
  else
    parts << node
  end
end


  








  

    #corrected_ancestor?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 148



def corrected_ancestor?(node)
  node.each_ancestor(:send).any? { |ancestor| @corrected_nodes&.include?(ancestor) }
end


  








  

    #double_quoted?(str_node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 211



def double_quoted?(str_node)
  str_node.loc.begin && str_node.source.start_with?('"')
end


  








  

    #file_keyword?(str_node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 203



def file_keyword?(str_node)
  str_node.source == '__FILE__' && !str_node.parent.dstr_type?
end


  








  

    #find_topmost_plus_node(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 117



def find_topmost_plus_node(node)
  current = node
  while (parent = current.parent) && plus_node?(parent)
    current = parent
  end
  current
end


  








  

    #handle_quotes(parts)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 197



def handle_quotes(parts)
  parts.map do |part|
    part == '"' ? '\"' : part
  end
end


  








  

    #heredoc?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 125



def heredoc?(node)
  node.each_descendant(:any_str).any?(&:heredoc?)
end


  








  

    #interpolation_formed?(preceding, part)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 165



def interpolation_formed?(preceding, part)
  part.start_with?('{', '@', '$') && preceding.match?(/(?<!\\)(?:\\\\)*#\z/)
end


  








  

    #join_parts(parts)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 158



def join_parts(parts)
  parts.each_with_object(+'') do |part, result|
    result.insert(-2, '\\') if interpolation_formed?(result, part)
    result << part
  end
end


  








  

    #line_end_concatenation?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 107



def line_end_concatenation?(node)
  # If the concatenation happens at the end of the line,
  # and both the receiver and argument are strings, allow
  # `Style/LineEndConcatenation` to handle it instead.
  node.receiver.str_type? &&
    node.first_argument.str_type? &&
    node.multiline? &&
    node.source.match?(/\+\s*\n/)
end


  








  

    #mode   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 215



def mode
  cop_config['Mode'].to_sym
end


  








  

    #on_new_investigation  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 76



def on_new_investigation
  @corrected_nodes = nil
end


  








  

    #on_send(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 80



def on_send(node)
  return unless string_concatenation?(node)
  return if line_end_concatenation?(node)

  topmost_plus_node = find_topmost_plus_node(node)
  return if heredoc?(topmost_plus_node)

  parts = collect_parts(topmost_plus_node)
  return if mode == :conservative && !parts.first.str_type?

  register_offense(topmost_plus_node, parts)
end


  








  

    #plus_node?(node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 140



def plus_node?(node)
  node.send_type? && node.method?(:+)
end


  








  

    #register_offense(topmost_plus_node, parts)   (private)
  

  [ GitHub ]


  

  


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



def register_offense(topmost_plus_node, parts)
  add_offense(topmost_plus_node) do |corrector|
    correctable_parts = parts.none? { |part| uncorrectable?(part) }
    if correctable_parts && !corrected_ancestor?(topmost_plus_node)
      corrector.replace(topmost_plus_node, replacement(parts))

      @corrected_nodes ||= Set.new.compare_by_identity
      @corrected_nodes.add(topmost_plus_node)
    end
  end
end


  








  

    #replacement(parts)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 152



def replacement(parts)
  interpolated_parts = parts.map { |part| adjust_str(part) }

  "\"#{join_parts(handle_quotes(interpolated_parts))}\""
end


  








  

    #single_quoted?(str_node)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 207



def single_quoted?(str_node)
  str_node.loc.begin && str_node.source.start_with?("'")
end


  








  

    #string_concatenation?(node)  
  

  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 69



def_node_matcher :string_concatenation?, <<~PATTERN
  {
    (send str_type? :+ _)
    (send _ :+ str_type?)
  }
PATTERN


  








  

    #uncorrectable?(part)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/rubocop/cop/style/string_concatenation.rb', line 144



def uncorrectable?(part)
  part.multiline? || part.each_descendant(:any_block).any?
end