class RuboCop::Cop::Lint::ShadowedException
Checks for a rescued exception that get shadowed by a less specific exception being rescued before a more specific exception is rescued.
An exception is considered shadowed if it is rescued after its ancestor is, or if it and its ancestor are both rescued in the same `rescue` statement. In both cases, the more specific rescue is unnecessary because it is covered by rescuing the less specific exception. (ie. `rescue Exception, StandardError` has the same behavior whether `StandardError` is included or not, because all “StandardError“s are rescued by `rescue Exception`).
@example
# bad begin something rescue Exception handle_exception rescue StandardError handle_standard_error end # bad begin something rescue Exception, StandardError handle_error end # good begin something rescue StandardError handle_standard_error rescue Exception handle_exception end # good, however depending on runtime environment. # # This is a special case for system call errors. # System dependent error code depends on runtime environment. # For example, whether `Errno::EAGAIN` and `Errno::EWOULDBLOCK` are # the same error code or different error code depends on environment. # This good case is for `Errno::EAGAIN` and `Errno::EWOULDBLOCK` with # the same error code. begin something rescue Errno::EAGAIN, Errno::EWOULDBLOCK handle_standard_error end
Constants
- MSG
Public Instance Methods
on_rescue(node)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 67 def on_rescue(node) return if rescue_modifier?(node) _body, *rescues, _else = *node rescued_groups = rescued_groups_for(rescues) rescue_group_rescues_multiple_levels = rescued_groups.any? do |group| contains_multiple_levels_of_exceptions?(group) end return if !rescue_group_rescues_multiple_levels && sorted?(rescued_groups) add_offense(offense_range(rescues)) end
Private Instance Methods
compare_exceptions(exception, other_exception)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 101 def compare_exceptions(exception, other_exception) if system_call_err?(exception) && system_call_err?(other_exception) # This condition logic is for special case. # System dependent error code depends on runtime environment. # For example, whether `Errno::EAGAIN` and `Errno::EWOULDBLOCK` are # the same error code or different error code depends on runtime # environment. This checks the error code for that. exception.const_get(:Errno) != other_exception.const_get(:Errno) && exception <=> other_exception else exception && other_exception && exception <=> other_exception end end
contains_multiple_levels_of_exceptions?(group)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 94 def contains_multiple_levels_of_exceptions?(group) # Always treat `Exception` as the highest level exception. return true if group.size > 1 && group.include?(Exception) group.combination(2).any? { |a, b| compare_exceptions(a, b) } end
evaluate_exceptions(group)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 119 def evaluate_exceptions(group) rescued_exceptions = group.exceptions if rescued_exceptions.any? rescued_exceptions.each_with_object([]) do |exception, converted| # FIXME: Workaround `rubocop:disable` comment for JRuby. # https://github.com/jruby/jruby/issues/6642 # rubocop:disable Style/RedundantBegin begin RuboCop::Util.silence_warnings do # Avoid printing deprecation warnings about constants converted << Kernel.const_get(exception.source) end rescue NameError converted << nil end # rubocop:enable Style/RedundantBegin end else # treat an empty `rescue` as `rescue StandardError` [StandardError] end end
find_shadowing_rescue(rescues)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 158 def find_shadowing_rescue(rescues) rescued_groups = rescued_groups_for(rescues) rescued_groups.zip(rescues).each do |group, res| return res if contains_multiple_levels_of_exceptions?(group) end rescued_groups.each_cons(2).with_index do |group_pair, i| return rescues[i] unless sorted?(group_pair) end end
offense_range(rescues)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 84 def offense_range(rescues) shadowing_rescue = find_shadowing_rescue(rescues) expression = shadowing_rescue.loc.expression range_between(expression.begin_pos, expression.end_pos) end
rescued_groups_for(rescues)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 90 def rescued_groups_for(rescues) rescues.map { |group| evaluate_exceptions(group) } end
sorted?(rescued_groups)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 143 def sorted?(rescued_groups) rescued_groups.each_cons(2).all? do |x, y| if x.include?(Exception) false elsif y.include?(Exception) || # consider sorted if a group is empty or only contains # `nil`s x.none? || y.none? true else (x <=> y || 0) <= 0 end end end
system_call_err?(error)
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# File lib/rubocop/cop/lint/shadowed_exception.rb, line 115 def system_call_err?(error) error && error.ancestors[1] == SystemCallError end