Class: DiffLineMapper

Inherits:
Object
  • Object
show all
Defined in:
lib/vimamsa/diff_buffer.rb

Overview

Map a “line number in a unified diff output” to the corresponding line number in the *new/changed file* (the + side).

Key idea:

@@ -old_start,old_count +new_start,new_count @@

sets starting counters. Then walk each hunk line:

' ' => old++, new++
'-' => old++
'+' => new++

If the target diff line is:

' ' or '+' => it corresponds to current new line (before increment)
'-'        => it has no new-file line (deleted). We return nil.

Constant Summary collapse

HUNK_RE = 
/^@@\s+-(\d+)(?:,(\d+))?\s+\+(\d+)(?:,(\d+))?\s+@@/

Instance Method Summary collapse

Constructor Details

#initialize(diff_text) ⇒ DiffLineMapper

Returns a new instance of DiffLineMapper.



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# File 'lib/vimamsa/diff_buffer.rb', line 18

def initialize(diff_text)
  @lines = diff_text.lines
end

Instance Method Details

#new_line_for_diff_lineno(diff_lineno) ⇒ Object

Given a 1-based line number in the diff output, return:

- Integer: 1-based line number in the new file
- nil:     if the diff line is a deletion ('-') or cannot be mapped

Raises:

  • (ArgumentError) 


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# File 'lib/vimamsa/diff_buffer.rb', line 25

def new_line_for_diff_lineno(diff_lineno)
  raise ArgumentError, "diff line number must be >= 1" if diff_lineno.to_i < 1
  idx = diff_lineno.to_i - 1
  return nil if idx >= @lines.length

  old = nil
  new_ = nil
  in_hunk = false

  @lines.each_with_index do |line, i|
    if (m = line.match(HUNK_RE))
      old = m[1].to_i
      new_ = m[3].to_i
      in_hunk = true
      next
    end

    next unless in_hunk

    if line.start_with?('--- ', '+++ ')
      in_hunk = false
      old = new_ = nil
      next
    end

    if i == idx
      return nil unless new_
      case line.getbyte(0)
      when '+'.ord then return new_
      when ' '.ord then return new_
      when '-'.ord then return nil
      else              return nil
      end
    end

    next unless old && new_

    case line.getbyte(0)
    when ' '.ord then old += 1; new_ += 1
    when '-'.ord then old += 1
    when '+'.ord then new_ += 1
    end
  end

  nil
end