Class: RuboCop::Cop::Lint::UselessAssignment
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
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Instance Chain:
self,
::RuboCop::Cop::RangeHelp ,
::RuboCop::Cop::Base ,
::RuboCop::Cop::AutocorrectLogic ,
::RuboCop::Cop::IgnoredNode ,
::RuboCop::Util ,
RuboCop::AST::Sexp
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Inherits: |
RuboCop::Cop::Base
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Defined in: | lib/rubocop/cop/lint/useless_assignment.rb |
Overview
Checks for every useless assignment to local variable in every
scope.
The basic idea for this cop was from the warning of ruby -cw
:
assigned but unused variable - foo
Currently this cop has advanced logic that detects unreferenced reassignments and properly handles varied cases such as branch, loop, rescue, ensure, etc.
This cop’s autocorrection avoids cases like a ||= 1
because removing assignment from
operator assignment can cause NameError if this assignment has been used to declare
a local variable. For example, replacing a ||= 1
with a || 1
may cause
"undefined local variable or method `a' for main:Object (NameError)".
Note
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Given the assignment foo = 1, bar = 2 , removing unused variables
can lead to a syntax error, so this case is not autocorrected.
|
Constant Summary
-
MSG =
# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 45'Useless assignment to variable - `%<variable>s`.'
::RuboCop::Cop::Base
- Inherited
EMPTY_OFFENSES, RESTRICT_ON_SEND
::RuboCop::Cop::RangeHelp
- Included
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 |
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 |
::RuboCop::ExcludeLimit
- Extended
exclude_limit | Sets up a configuration option to have an exclude limit tracked. |
transform |
Instance Attribute Summary
::RuboCop::Cop::Base
- Inherited
::RuboCop::Cop::AutocorrectLogic
- Included
Instance Method Summary
- #after_leaving_scope(scope, _variable_table)
- #autocorrect(corrector, assignment)
- #chained_assignment?(node) ⇒ Boolean
-
#check_for_unused_assignments(variable)
Metrics/PerceivedComplexity, Metrics/CyclomaticComplexity.
- #collect_variable_like_names(scope)
-
#message_for_useless_assignment(assignment)
Metrics/PerceivedComplexity, Metrics/CyclomaticComplexity.
- #message_specification(assignment, variable)
- #multiple_assignment_message(variable_name)
- #offense_range(assignment)
- #operator_assignment_message(scope, assignment)
- #remove_exception_assignment_part(corrector, node)
- #remove_local_variable_assignment_part(corrector, node)
- #remove_trailing_character_from_operator(corrector, node)
- #rename_variable_with_underscore(corrector, node)
- #replace_named_capture_group_with_non_capturing_group(corrector, node, variable_name)
-
#return_value_node_of_scope(scope)
TODO: More precise handling (rescue, ensure, nested begin, etc.).
- #sequential_assignment?(node) ⇒ Boolean
- #similar_name_message(variable)
- #variable_like_method_invocation?(node) ⇒ Boolean
::RuboCop::Cop::RangeHelp
- Included
#add_range, #column_offset_between, | |
#contents_range | A range containing only the contents of a literal with delimiters (e.g. |
#directions, | |
#effective_column | Returns the column attribute of the range, except if the range is on the first line and there’s a byte order mark at the beginning of that line, in which case 1 is subtracted from the column value. |
#final_pos, #move_pos, #move_pos_str, #range_between, #range_by_whole_lines, #range_with_comments, #range_with_comments_and_lines, #range_with_surrounding_comma, #range_with_surrounding_space, #source_range |
::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 |
#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
#disable_offense, #disable_offense_at_end_of_line, #disable_offense_before_and_after, #disable_offense_with_eol_or_surround_comment, #heredoc_range, #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, #range_overlaps_offense?, #string_continuation?, #surrounding_heredoc?, #surrounding_percent_array? |
::RuboCop::Cop::IgnoredNode
- Included
Constructor Details
This class inherits a constructor from RuboCop::Cop::Base
Class Method Details
.joining_forces
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 47
def self.joining_forces VariableForce end
Instance Method Details
#after_leaving_scope(scope, _variable_table)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 51
def after_leaving_scope(scope, _variable_table) scope.variables.each_value { |variable| check_for_unused_assignments(variable) } end
#autocorrect(corrector, assignment)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 165
def autocorrect(corrector, assignment) if assignment.exception_assignment? remove_exception_assignment_part(corrector, assignment.node) elsif assignment.multiple_assignment? || assignment.rest_assignment? || assignment.for_assignment? rename_variable_with_underscore(corrector, assignment.node) elsif assignment.operator_assignment? remove_trailing_character_from_operator(corrector, assignment.node) elsif assignment.regexp_named_capture? replace_named_capture_group_with_non_capturing_group(corrector, assignment.node, assignment.variable.name) else remove_local_variable_assignment_part(corrector, assignment.node) end end
#chained_assignment?(node) ⇒ Boolean
# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 106
def chained_assignment?(node) node.respond_to?(:expression) && node.expression&.lvasgn_type? end
#check_for_unused_assignments(variable)
Metrics/PerceivedComplexity, Metrics/CyclomaticComplexity
# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 56
def check_for_unused_assignments(variable) return if variable.should_be_unused? variable.assignments.reverse_each do |assignment| assignment_node = assignment.node next if assignment.used? || part_of_ignored_node?(assignment_node) = (assignment) range = offense_range(assignment) add_offense(range, message: ) do |corrector| # In cases like `x = 1, y = 2`, where removing a variable would cause a syntax error, # and where changing `x ||= 1` to `x = 1` would cause `NameError`, # the autocorrect will be skipped, even if the variable is unused. if sequential_assignment?(assignment_node) || assignment_node.parent&.or_asgn_type? next end autocorrect(corrector, assignment) end ignore_node(assignment_node) if chained_assignment?(assignment_node) end end
#collect_variable_like_names(scope)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 149
def collect_variable_like_names(scope) names = scope.each_node.with_object(Set.new) do |node, set| set << node.method_name if variable_like_method_invocation?(node) end variable_names = scope.variables.each_value.map(&:name) names.merge(variable_names) end
#message_for_useless_assignment(assignment)
Metrics/PerceivedComplexity, Metrics/CyclomaticComplexity
# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 82
def (assignment) variable = assignment.variable format(MSG, variable: variable.name) + (assignment, variable).to_s end
#message_specification(assignment, variable)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 110
def (assignment, variable) if assignment.multiple_assignment? (variable.name) elsif assignment.operator_assignment? (variable.scope, assignment) else (variable) end end
#multiple_assignment_message(variable_name)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 120
def (variable_name) " Use `_` or `_#{variable_name}` as a variable name to indicate " \ "that it won't be used." end
#offense_range(assignment)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 88
def offense_range(assignment) if assignment.regexp_named_capture? assignment.node.children.first.source_range else assignment.node.loc.name end end
#operator_assignment_message(scope, assignment)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 125
def (scope, assignment) return_value_node = return_value_node_of_scope(scope) return unless assignment. .equal?(return_value_node) " Use `#{assignment.operator.delete_suffix('=')}` instead of `#{assignment.operator}`." end
#remove_exception_assignment_part(corrector, node)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 182
def remove_exception_assignment_part(corrector, node) corrector.remove( range_between( (node.parent.children.first&.source_range || node.parent.location.keyword).end_pos, node.source_range.end_pos ) ) end
#remove_local_variable_assignment_part(corrector, node)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 206
def remove_local_variable_assignment_part(corrector, node) corrector.replace(node, node.expression.source) end
#remove_trailing_character_from_operator(corrector, node)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 195
def remove_trailing_character_from_operator(corrector, node) corrector.remove(node.parent.location.operator.end.adjust(begin_pos: -1)) end
#rename_variable_with_underscore(corrector, node)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 191
def rename_variable_with_underscore(corrector, node) corrector.replace(node, '_') end
#replace_named_capture_group_with_non_capturing_group(corrector, node, variable_name)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 199
def replace_named_capture_group_with_non_capturing_group(corrector, node, variable_name) corrector.replace( node.children.first, node.children.first.source.sub(/\(\?<#{variable_name}>/, '(?:') ) end
#return_value_node_of_scope(scope)
TODO: More precise handling (rescue, ensure, nested begin, etc.)
# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 139
def return_value_node_of_scope(scope) body_node = scope.body_node if body_node.begin_type? body_node.children.last else body_node end end
#sequential_assignment?(node) ⇒ Boolean
# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 96
def sequential_assignment?(node) if node.lvasgn_type? && node.expression&.array_type? && node.each_descendant.any?(&:assignment?) return true end return false unless node.parent sequential_assignment?(node.parent) end
#similar_name_message(variable)
[ GitHub ]# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 132
def (variable) variable_like_names = collect_variable_like_names(variable.scope) similar_name = NameSimilarity.find_similar_name(variable.name, variable_like_names) " Did you mean `#{similar_name}`?" if similar_name end
#variable_like_method_invocation?(node) ⇒ Boolean
# File 'lib/rubocop/cop/lint/useless_assignment.rb', line 158
def variable_like_method_invocation?(node) return false unless node.send_type? node.receiver.nil? && !node.arguments? end