Colour the diff output (#44)

src/tox_ini_fmt/__main__.py

@@ -1,11 +1,25 @@
 import difflib
 import sys
 from pathlib import Path
-from typing import Optional, Sequence
+from typing import Iterable, Optional, Sequence
 
 from tox_ini_fmt.cli import cli_args
 from tox_ini_fmt.formatter import format_tox_ini
 
+GREEN = "\u001b[32m"
+RED = "\u001b[31m"
+RESET = "\u001b[0m"
+
+
+def color_diff(diff: Iterable[str]) -> Iterable[str]:
+ for line in diff:
+ if line.startswith("+"):
+ yield GREEN + line + RESET
+ elif line.startswith("-"):
+ yield RED + line + RESET
+ else:
+ yield line
+
 
 def run(args: Optional[Sequence[str]] = None) -> int:
  opts = cli_args(sys.argv[1:] if args is None else args)
@@ -26,6 +40,7 @@ def run(args: Optional[Sequence[str]] = None) -> int:
  else []
  )
  if diff:
+ diff = color_diff(diff)
  print("\n".join(diff)) # print diff on change
  else:
  print(f"no change for {name}")

tests/test_main.py

@@ -1,6 +1,48 @@
+import difflib
+
 import pytest
 
-from tox_ini_fmt.__main__ import run
+import tox_ini_fmt.__main__
+from tox_ini_fmt.__main__ import GREEN, RED, RESET, color_diff, run
+
+
+def test_color_diff():
+ # Arrange
+ before = """
+ abc
+ def
+ ghi
+"""
+ after = """
+ abc
+ abc
+ def
+"""
+ diff = difflib.unified_diff(before.splitlines(), after.splitlines())
+ expected_lines = f"""
+{RED}---
+{RESET}
+{GREEN}+++
+{RESET}
+@@ -1,4 +1,4 @@
+
+
+ abc
+{GREEN}+ abc{RESET}
+ def
+{RED}- ghi{RESET}
+""".strip().splitlines()
+
+ # Act
+ diff = color_diff(diff)
+
+ # Assert
+ output_lines = [line.rstrip() for line in "\n".join(diff).splitlines()]
+ assert output_lines == expected_lines
+
+
+def no_color(diff):
+ return diff
 
 
 @pytest.mark.parametrize("in_place", [True, False])
@@ -18,6 +60,7 @@
  ],
 )
 def test_main(tmp_path, capsys, in_place, start, outcome, output, monkeypatch, cwd):
+ monkeypatch.setattr(tox_ini_fmt.__main__, "color_diff", no_color)
  if cwd:
  monkeypatch.chdir(tmp_path)
  tox_ini = tmp_path / "tox.ini"