class RuboCop::Cop::Style::RedundantSort
Identifies instances of sorting and then taking only the first or last element. The same behavior can be accomplished without a relatively expensive sort by using `Enumerable#min` instead of sorting and taking the first element and `Enumerable#max` instead of sorting and taking the last element. Similarly, `Enumerable#min_by` and `Enumerable#max_by` can replace `Enumerable#sort_by` calls after which only the first or last element is used.
@safety
This cop is unsafe, because `sort...last` and `max` may not return the same element in all cases. In an enumerable where there are multiple elements where `a <=> b == 0`, or where the transformation done by the `sort_by` block has the same result, `sort.last` and `max` (or `sort_by.last` and `max_by`) will return different elements. `sort.last` will return the last element but `max` will return the first element. For example: [source,ruby] ---- class MyString < String; end strings = [MyString.new('test'), 'test'] strings.sort.last.class #=> String strings.max.class #=> MyString ---- [source,ruby] ---- words = %w(dog horse mouse) words.sort_by { |word| word.length }.last #=> 'mouse' words.max_by { |word| word.length } #=> 'horse' ----
@example
# bad [2, 1, 3].sort.first [2, 1, 3].sort[0] [2, 1, 3].sort.at(0) [2, 1, 3].sort.slice(0) # good [2, 1, 3].min # bad [2, 1, 3].sort.last [2, 1, 3].sort[-1] [2, 1, 3].sort.at(-1) [2, 1, 3].sort.slice(-1) # good [2, 1, 3].max # bad arr.sort_by(&:foo).first arr.sort_by(&:foo)[0] arr.sort_by(&:foo).at(0) arr.sort_by(&:foo).slice(0) # good arr.min_by(&:foo) # bad arr.sort_by(&:foo).last arr.sort_by(&:foo)[-1] arr.sort_by(&:foo).at(-1) arr.sort_by(&:foo).slice(-1) # good arr.max_by(&:foo)
Constants
- MSG
- RESTRICT_ON_SEND
Public Instance Methods
on_send(node)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 104 def on_send(node) ancestor, sort_node, sorter, accessor = find_redundant_sort(node.parent, node.parent&.parent) return unless ancestor register_offense(ancestor, sort_node, sorter, accessor) end
Private Instance Methods
accessor_start(node)
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This gets the start of the accessor whether it has a dot (e.g. `.first`) or doesn't (e.g. `[0]`)
# File lib/rubocop/cop/style/redundant_sort.rb, line 192 def accessor_start(node) if node.loc.dot node.loc.dot.begin_pos else node.loc.selector.begin_pos end end
arg_node(node)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 182 def arg_node(node) node.arguments.first end
arg_value(node)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 186 def arg_value(node) arg_node(node).nil? ? nil : arg_node(node).node_parts.first end
autocorrect(corrector, node, sort_node, sorter, accessor)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 147 def autocorrect(corrector, node, sort_node, sorter, accessor) # Remove accessor, e.g. `first` or `[-1]`. corrector.remove(range_between(accessor_start(node), node.loc.expression.end_pos)) # Replace "sort" or "sort_by" with the appropriate min/max method. corrector.replace(sort_node.loc.selector, suggestion(sorter, accessor, arg_value(node))) # Replace to avoid syntax errors when followed by a logical operator. replace_with_logical_operator(corrector, node) if with_logical_operator?(node) end
base(accessor, arg)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 165 def base(accessor, arg) if accessor == :first || arg&.zero? 'min' elsif accessor == :last || arg == -1 'max' end end
find_redundant_sort(*nodes)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 114 def find_redundant_sort(*nodes) nodes.each do |node| if (sort_node, sorter, accessor = redundant_sort?(node)) return [node, sort_node, sorter, accessor] end end nil end
message(node, sorter, accessor)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 135 def message(node, sorter, accessor) accessor_source = range_between( node.loc.selector.begin_pos, node.loc.expression.end_pos ).source format(MSG, suggestion: suggestion(sorter, accessor, arg_value(node)), sorter: sorter, accessor_source: accessor_source) end
offense_range(sort_node, node)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 131 def offense_range(sort_node, node) range_between(sort_node.loc.selector.begin_pos, node.loc.expression.end_pos) end
register_offense(node, sort_node, sorter, accessor)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 124 def register_offense(node, sort_node, sorter, accessor) message = message(node, sorter, accessor) add_offense(offense_range(sort_node, node), message: message) do |corrector| autocorrect(corrector, node, sort_node, sorter, accessor) end end
replace_with_logical_operator(corrector, node)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 156 def replace_with_logical_operator(corrector, node) corrector.insert_after(node.child_nodes.first, " #{node.parent.loc.operator.source}") corrector.remove(node.parent.loc.operator) end
suffix(sorter)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 173 def suffix(sorter) case sorter when :sort '' when :sort_by '_by' end end
suggestion(sorter, accessor, arg)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 161 def suggestion(sorter, accessor, arg) base(accessor, arg) + suffix(sorter) end
with_logical_operator?(node)
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# File lib/rubocop/cop/style/redundant_sort.rb, line 200 def with_logical_operator?(node) return unless (parent = node.parent) parent.or_type? || parent.and_type? end