Class: Contrast::Agent::Assess::Policy::Propagator::Insert

Inherits:
Base
  • Object
show all
Defined in:
lib/contrast/agent/assess/policy/propagator/insert.rb

Overview

Propagation that results in all the tags of the source being applied to the target at the point of insertion. The target’s preexisting tags are shifted to account for this insertion.

Class Method Summary collapse

Methods inherited from Base

find_source, tracked_value?

Class Method Details

.propagate(propagation_node, preshift, target) ⇒ Object

For the source, append its tags to the target. Once the tag is applied, shift it to the location of the insert Unlike additive propagation, this currently only supports one source We assume that insert changes the preshift target



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# File 'lib/contrast/agent/assess/policy/propagator/insert.rb', line 18

def propagate propagation_node, preshift, target
  properties = Contrast::Agent::Assess::Tracker.properties(target)
  return unless properties

  source = find_source(propagation_node.sources[1], preshift)

  patcher_target = propagation_node.targets[0]
  preshift_target = case patcher_target
                    when Contrast::Utils::ObjectShare::OBJECT_KEY
                      preshift.object
                    else
                      preshift.args[int]
                    end

  # Find the first difference between the source to which
  # we inserted and the result. That is the insertion
  # point on which all tags need to be adjusted
  # If the insertion point is the end of the string, preshift length is returned
  # https://stackoverflow.com/questions/31714522/find-the-first-differing-character-between-two-strings-in-ruby
  insert_point = (0...preshift_target.length).find { |i| preshift_target[i] != target[i] } || preshift_target.length
  # Depending what's inserted, we might be wrong. For instance, inserting 'foo'
  # into 'asdfasdf' could result in 'asdfoofasdf'. we'd be off by one b/c of the 'f'
  insert_point = target.rindex(source, insert_point)
  overflow = insert_point...(insert_point + source.length)

  # handle shifting the inserted range
  properties.shift_tags([overflow])

  properties.copy_from(source, target, insert_point, propagation_node.untags)
  properties.cleanup_tags
end