Fix: use DARK_GRAY for unmapped content type groups in CLI output (fixes #1243)

[shivamtiwari3]

Summary

Fixes #1243.

The Python CLI's colored output was nearly invisible on light-background terminals because content type groups not explicitly listed in color_by_group (including "text", "unknown", "application", "font", "inode") all fell back to colors.WHITE (\033[1;37m — bright white), which disappears on white terminal backgrounds.

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Root Cause

In magika_client.py:L312, color_by_group.get(group, colors.WHITE) was used to select the ANSI color. The dict covered 7 groups but the model has 12, so 5 groups — including the common "text" and "unknown" — silently fell back to bright white. On a light-background terminal, this produces output that looks like light gray at best and invisible at worst.

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Solution

Two targeted changes in python/src/magika/cli/magika_client.py:

1. Add explicit entries for "text" and "unknown" in color_by_group, both mapped to colors.DARK_GRAY.
2. Change the dict fallback from colors.WHITE to colors.DARK_GRAY so any future unmapped groups also display visibly.

DARK_GRAY (\033[1;30m — bold/bright black) renders as dark gray on light terminals (clearly visible on white) and as dark gray on dark terminals (readable, appropriate for lower-confidence output). This matches the approach suggested in the issue: "Darkening the gray should solve the problem nicely, without being too hard to see on a dark background."

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Testing

• Added test_colored_output_visible_on_light_background_terminals in python/tests/test_python_magika_client.py — reproduces the exact scenario from the issue: runs the CLI with --colors on a plain .txt file (classified as group="text"), asserts the output contains DARK_GRAY and does not contain WHITE.
• All 32 existing tests continue to pass (uv run pytest tests -m "not slow")
• ruff check, ruff format, and mypy all pass clean

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Checklist

• Fixes the root cause (bright-white fallback replaced with dark gray)
• New test covers the exact failing scenario from the issue
• All existing tests pass
• No unrelated changes
• Code style matches project conventions (ruff + mypy clean)
• Read CONTRIBUTING.md

[gemini-code-assist]

Code Review

This pull request correctly addresses the issue of nearly invisible CLI output on light-background terminals by changing the fallback color for unmapped content type groups to DARK_GRAY. The changes are logical, and the inclusion of a new regression test ensures the fix is robust. I have one suggestion to improve the new test's implementation for handling temporary files, making it more idiomatic and cleaner.

[gemini-code-assist]

For cleaner and more idiomatic temporary file handling in tests, consider using pytest's built-in tmp_path fixture. It simplifies the code by automatically managing the lifecycle of temporary directories and files, removing the need for tempfile.NamedTemporaryFile with delete=False and a manual try...finally cleanup block.

def test_colored_output_visible_on_light_background_terminals(tmp_path: Path) -> None:
    """Regression test for https://github.com/google/magika/issues/1243.

    The fallback color for content type groups not explicitly mapped in
    color_by_group must not be bright white (\033[1;37m), which is nearly
    invisible on light-background terminals. DARK_GRAY (\033[1;30m) is
    visible on both dark and light backgrounds.
    """
    python_root_dir = Path(__file__).parent.parent
    python_magika_client_path = (
        python_root_dir / 'src' / 'magika' / 'cli' / 'magika_client.py'
    ).resolve()

    # Write a plain text file — classified as group='text', which previously
    # fell through to the bright-white fallback color.
    test_file = tmp_path / 'test.txt'
    test_file.write_text('Hello, world!\n')

    try:
        result = subprocess.run(
            [str(python_magika_client_path), '--colors', str(test_file)],
            capture_output=True,
            text=True,
            check=True,
        )
        output = result.stdout
        # The output must not contain the bright-white ANSI code, which is
        # invisible on white/light-background terminals.
        assert colors.WHITE not in output, (
            f'Output used bright-white ({repr(colors.WHITE)}), which is '
            'invisible on light-background terminals. Use DARK_GRAY instead.'
        )
        # DARK_GRAY must be present so that content types in the 'text' group
        # (and any other unmapped group) are readable on light terminals.
        assert colors.DARK_GRAY in output, (
            f'Expected DARK_GRAY ({repr(colors.DARK_GRAY)}) in colored output '
            'for a plain-text file, but it was not found.'
        )
    finally:
        test_file.unlink(missing_ok=True)

[shivamtiwari3]

Thanks for the review! Applied the suggestion — switched to pytest's tmp_path fixture, which also lets us remove the try/finally cleanup block and the tempfile import entirely since tmp_path handles lifecycle automatically.