Class: PatternPatch::Utilities

Inherits:
Object
  • Object
show all
Defined in:
lib/pattern_patch/utilities.rb

Class Method Summary collapse

Class Method Details

.apply_patch(contents, regexp, text, global, mode, offset) ⇒ Object

Add the specified text after the specified pattern. Returns a modified copy of the string.

:contents: A string to modify, e.g. the contents of a file :regexp: A regular expression specifying a pattern to be matched :text: Text to be appended to the specified pattern :global: Boolean flag. If true, patch all occurrences of the regex. :mode: :append, :prepend or :replace to specify how to apply the patch :offset: Starting position for matching



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# File 'lib/pattern_patch/utilities.rb', line 13

def apply_patch(contents, regexp, text, global, mode, offset)
  search_position = offset
  while (matches = regexp.match(contents, search_position))
    patched_pattern =
      case mode
      when :append
        "#{matches[0]}#{text.apply_matches matches}"
      when :prepend
        "#{text.apply_matches matches}#{matches[0]}"
      when :replace
        matches[0].sub regexp, text
      else
        raise ArgumentError, "Invalid mode argument. Specify :append, :prepend or :replace."
      end

    contents = "#{matches.pre_match}#{patched_pattern}#{matches.post_match}"
    break unless global
    search_position = matches.pre_match.length + patched_pattern.length
  end
  contents
end

.revert_patch(contents, regexp, text, global, mode, offset) ⇒ Object

Reverts a patch. Use the same arguments that were supplied to apply_patch. The mode argument can only be :append or :prepend. Patches using :replace cannot be reverted. Returns a modified copy of the string.

:contents: A string to modify, e.g. the contents of a file :regexp: A regular expression specifying a pattern to be matched :text: Text to be appended to the specified pattern :global: Boolean flag. If true, patch all occurrences of the regex. :mode: :append or :prepend. :replace patches cannot be reverted automatically. :offset: Starting position for matching



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# File 'lib/pattern_patch/utilities.rb', line 46

def revert_patch(contents, regexp, text, global, mode, offset)
  search_position = offset
  regexp_string = regexp.to_s

  patched_regexp =
    case mode
    when :append
      /#{regexp_string}#{text}/m
    when :prepend
      # TODO: Capture groups aren't currently revertible in :prepend mode.
      # This patched regexp can turn into something like /\1.*(\d+)/.
      # The capture group reference cannot occur in the regexp before definition
      # of the group. This would have to be transformed to something like
      # /(\d+).*\1/. Patch reversion is probably not a major use case right
      # now, so ignore for the moment.
      /#{text}#{regexp_string}/m
    else
      raise ArgumentError, "Invalid mode argument. Specify :append or :prepend."
    end

  while (matches = patched_regexp.match(contents, search_position))
    reverted_text = matches[0].sub(text.apply_matches(matches), '')
    contents = "#{matches.pre_match}#{reverted_text}#{matches.post_match}"
    break unless global
    search_position = matches.pre_match.length + reverted_text.length
  end

  contents
end