Source code for ffc.uflacs.language.format_lines

# -*- coding: utf-8 -*-
# Copyright (C) 2011-2017 Martin Sandve Alnæs
#
# This file is part of UFLACS.
#
# UFLACS is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# UFLACS is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with UFLACS. If not, see <http://www.gnu.org/licenses/>.

"""Tools for indentation-aware code string stitching.

When formatting an AST into a string, it's better to collect
lists of snippets and then join them than adding the pieces
continually, which gives O(n^2) behaviour w.r.t. AST size n.
"""


class Indented(object):
    """Class to mark a collection of snippets for indentation.

    This way nested indentations can be handled by adding the prefix
    spaces only once to each line instead of splitting and indenting
    substrings repeatedly.
    """
    # Try to keep memory overhead low:
    __slots__ = ("body",)
    def __init__(self, body):
        # Body can be any valid snippet format
        self.body = body

def iter_indented_lines(snippets, level=0):
    """Iterate over indented string lines from a snippets data structure.

    The snippets object can be built recursively using the following types:

    - str: Split and yield as one line at a time indented to the appropriate level.

    - Indented: Yield the lines within this object indented by one level.

    - tuple,list: Yield lines from recursive application of this function to list items.

    """
    tabsize = 4
    indentation = ' ' * (tabsize * level)
    if isinstance(snippets, str):
        for line in snippets.split("\n"):
            yield indentation + line
    elif isinstance(snippets, Indented):
        for line in iter_indented_lines(snippets.body, level+1):
            yield line
    elif isinstance(snippets, (tuple, list)):
        for part in snippets:
            for line in iter_indented_lines(part, level):
                yield line
    else:
        raise RuntimeError("Unexpected type %s:\n%s" % (type(snippets), str(snippets)))

def format_indented_lines(snippets, level=0):
    "Format recursive sequences of indented lines as one string."
    return "\n".join(iter_indented_lines(snippets, level))