Method _do_a_fancy_diff

Lib/doctest.py:1794–1815

(self, want, got, optionflags)

    # Should we do a fancy diff?
    def _do_a_fancy_diff(self, want, got, optionflags):
        # Not unless they asked for a fancy diff.
        if not optionflags & (REPORT_UDIFF |
                              REPORT_CDIFF |
                              REPORT_NDIFF):
            return False

        # If expected output uses ellipsis, a meaningful fancy diff is
        # too hard ... or maybe not.  In two real-life failures Tim saw,
        # a diff was a major help anyway, so this is commented out.
        # [todo] _ellipsis_match() knows which pieces do and don't match,
        # and could be the basis for a kick-ass diff in this case.
        ##if optionflags & ELLIPSIS and ELLIPSIS_MARKER in want:
        ##    return False

        # ndiff does intraline difference marking, so can be useful even
        # for 1-line differences.
        if optionflags & REPORT_NDIFF:
            return True

        # The other diff types need at least a few lines to be helpful.
        return want.count('\n') > 2 and got.count('\n') > 2

    def output_difference(self, example, got, optionflags):
        """