Module: Mutineer::ChangedLines

Defined in:
lib/mutineer/changed_lines.rb

Overview

Maps each source file to the set of NEW-side line numbers that changed since a given git ref, by parsing git diff --unified=0. Used to restrict mutations to only the diff (issue #2): on a PR you care whether the changed code is tested, so mutating just those lines is fast and actionable.

git is an external tool, not a gem dependency — shelling out is fine. The pure parse carries the logic; git_diff is injectable so it stays testable without invoking git.

Constant Summary collapse

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

Class Method Summary collapse

Class Method Details

.for(ref:, files:, project_root:, runner: method(:git_diff)) ⇒ Object

{ absolute_file_path => Set } of changed new-side lines per file. runner is injected so tests can supply canned diff text per file.



39
40
41
42
43
44
 
# File 'lib/mutineer/changed_lines.rb', line 39

def for(ref:, files:, project_root:, runner: method(:git_diff))
  files.each_with_object({}) do |file, acc|
    abs = File.expand_path(file, project_root)
    acc[abs] = parse(runner.call(ref, abs, project_root))
  end
end

.git_diff(ref, abs_file, project_root) ⇒ Object

stdout of git -C <root> diff --unified=0 <ref> -- <file>, "" on failure.



47
48
49
50
51
52
53
54
 
# File 'lib/mutineer/changed_lines.rb', line 47

def git_diff(ref, abs_file, project_root)
  out, _err, status = Open3.capture3(
    "git", "-C", project_root, "diff", "--unified=0", ref, "--", abs_file
  )
  status.success? ? out : ""
rescue StandardError
  ""
end

.parse(diff_text) ⇒ Object

Parse git diff --unified=0 output into the set of NEW-side line numbers added/modified. With --unified=0 each hunk's +c,d block is exactly the changed lines: c..c+d-1. d absent means 1 line; d == 0 is a pure deletion and contributes nothing.



24
25
26
27
28
29
30
31
32
33
34
35
 
# File 'lib/mutineer/changed_lines.rb', line 24

def parse(diff_text)
  lines = Set.new
  diff_text.each_line do |row|
    m = HUNK.match(row) or next
    start = m[1].to_i
    count = m[2].nil? ? 1 : m[2].to_i
    next if count.zero?

    lines.merge(start...(start + count))
  end
  lines
end