Function show_align_message

mypy/test/helpers.py:220–269

Align s1 and s2 so that the their first difference is highlighted. For example, if s1 is 'foobar' and s2 is 'fobar', display the following lines: E: foobar A: fobar ^ If s1 and s2 are long, only display a fragment of the strings around the first difference.

(s1: str, s2: str)

def show_align_message(s1: str, s2: str) -> None:
    """Align s1 and s2 so that the their first difference is highlighted.

    For example, if s1 is 'foobar' and s2 is 'fobar', display the
    following lines:

      E: foobar
      A: fobar
           ^

    If s1 and s2 are long, only display a fragment of the strings around the
    first difference. If s1 is very short, do nothing.
    """

    # Seeing what went wrong is trivial even without alignment if the expected
    # string is very short. In this case do nothing to simplify output.
    if len(s1) < 4:
        return

    maxw = 72  # Maximum number of characters shown

    sys.stderr.write("Alignment of first line difference:\n")

    trunc = False
    while s1[:30] == s2[:30]:
        s1 = s1[10:]
        s2 = s2[10:]
        trunc = True

    if trunc:
        s1 = "..." + s1
        s2 = "..." + s2

    max_len = max(len(s1), len(s2))
    extra = ""
    if max_len > maxw:
        extra = "..."

    # Write a chunk of both lines, aligned.
    sys.stderr.write(f"  E: {s1[:maxw]}{extra}\n")
    sys.stderr.write(f"  A: {s2[:maxw]}{extra}\n")
    # Write an indicator character under the different columns.
    sys.stderr.write("     ")
    for j in range(min(maxw, max(len(s1), len(s2)))):
        if s1[j : j + 1] != s2[j : j + 1]:
            sys.stderr.write("^")  # Difference
            break
        else:
            sys.stderr.write(" ")  # Equal
    sys.stderr.write("\n")


def clean_up(a: list[str]) -> list[str]: