util.py

# coding: utf-8

"""
some helper functions that might be generally useful
"""

from __future__ import absolute_import, print_function

from functools import partial
import re

from .compat import text_type, binary_type

if False:  # MYPY
    from typing import Any, Dict, Optional, List, Text  # NOQA
    from .compat import StreamTextType  # NOQA


class LazyEval(object):
    """
    Lightweight wrapper around lazily evaluated func(*args, **kwargs).

    func is only evaluated when any attribute of its return value is accessed.
    Every attribute access is passed through to the wrapped value.
    (This only excludes special cases like method-wrappers, e.g., __hash__.)
    The sole additional attribute is the lazy_self function which holds the
    return value (or, prior to evaluation, func and arguments), in its closure.
    """

    def __init__(self, func, *args, **kwargs):
        # type: (Any, Any, Any) -> None
        def lazy_self():
            # type: () -> Any
            return_value = func(*args, **kwargs)
            object.__setattr__(self, 'lazy_self', lambda: return_value)
            return return_value

        object.__setattr__(self, 'lazy_self', lazy_self)

    def __getattribute__(self, name):
        # type: (Any) -> Any
        lazy_self = object.__getattribute__(self, 'lazy_self')
        if name == 'lazy_self':
            return lazy_self
        return getattr(lazy_self(), name)

    def __setattr__(self, name, value):
        # type: (Any, Any) -> None
        setattr(self.lazy_self(), name, value)


RegExp = partial(LazyEval, re.compile)


# originally as comment
# https://github.com/pre-commit/pre-commit/pull/211#issuecomment-186466605
# if you use this in your code, I suggest adding a test in your test suite
# that check this routines output against a known piece of your YAML
# before upgrades to this code break your round-tripped YAML
def load_yaml_guess_indent(stream, **kw):
    # type: (StreamTextType, Any) -> Any
    """guess the indent and block sequence indent of yaml stream/string

    returns round_trip_loaded stream, indent level, block sequence indent
    - block sequence indent is the number of spaces before a dash relative to previous indent
    - if there are no block sequences, indent is taken from nested mappings, block sequence
      indent is unset (None) in that case
    """
    from .main import round_trip_load

    # load a yaml file guess the indentation, if you use TABs ...
    def leading_spaces(l):
        # type: (Any) -> int
        idx = 0
        while idx < len(l) and l[idx] == ' ':
            idx += 1
        return idx

    if isinstance(stream, text_type):
        yaml_str = stream  # type: Any
    elif isinstance(stream, binary_type):
        # most likely, but the Reader checks BOM for this
        yaml_str = stream.decode('utf-8')
    else:
        yaml_str = stream.read()
    map_indent = None
    indent = None  # default if not found for some reason
    block_seq_indent = None
    prev_line_key_only = None
    key_indent = 0
    for line in yaml_str.splitlines():
        rline = line.rstrip()
        lline = rline.lstrip()
        if lline.startswith('- '):
            l_s = leading_spaces(line)
            block_seq_indent = l_s - key_indent
            idx = l_s + 1
            while line[idx] == ' ':  # this will end as we rstripped
                idx += 1
            if line[idx] == '#':  # comment after -
                continue
            indent = idx - key_indent
            break
        if map_indent is None and prev_line_key_only is not None and rline:
            idx = 0
            while line[idx] in ' -':
                idx += 1
            if idx > prev_line_key_only:
                map_indent = idx - prev_line_key_only
        if rline.endswith(':'):
            key_indent = leading_spaces(line)
            idx = 0
            while line[idx] == ' ':  # this will end on ':'
                idx += 1
            prev_line_key_only = idx
            continue
        prev_line_key_only = None
    if indent is None and map_indent is not None:
        indent = map_indent
    return round_trip_load(yaml_str, **kw), indent, block_seq_indent


def configobj_walker(cfg):
    # type: (Any) -> Any
    """
    walks over a ConfigObj (INI file with comments) generating
    corresponding YAML output (including comments
    """
    from configobj import ConfigObj  # type: ignore

    assert isinstance(cfg, ConfigObj)
    for c in cfg.initial_comment:
        if c.strip():
            yield c
    for s in _walk_section(cfg):
        if s.strip():
            yield s
    for c in cfg.final_comment:
        if c.strip():
            yield c


def _walk_section(s, level=0):
    # type: (Any, int) -> Any
    from configobj import Section

    assert isinstance(s, Section)
    indent = u'  ' * level
    for name in s.scalars:
        for c in s.comments[name]:
            yield indent + c.strip()
        x = s[name]
        if u'\n' in x:
            i = indent + u'  '
            x = u'|\n' + i + x.strip().replace(u'\n', u'\n' + i)
        elif ':' in x:
            x = u"'" + x.replace(u"'", u"''") + u"'"
        line = u'{0}{1}: {2}'.format(indent, name, x)
        c = s.inline_comments[name]
        if c:
            line += u' ' + c
        yield line
    for name in s.sections:
        for c in s.comments[name]:
            yield indent + c.strip()
        line = u'{0}{1}:'.format(indent, name)
        c = s.inline_comments[name]
        if c:
            line += u' ' + c
        yield line
        for val in _walk_section(s[name], level=level + 1):
            yield val


# def config_obj_2_rt_yaml(cfg):
#     from .comments import CommentedMap, CommentedSeq
#     from configobj import ConfigObj
#     assert isinstance(cfg, ConfigObj)
#     #for c in cfg.initial_comment:
#     #    if c.strip():
#     #        pass
#     cm = CommentedMap()
#     for name in s.sections:
#         cm[name] = d = CommentedMap()
#
#
#     #for c in cfg.final_comment:
#     #    if c.strip():
#     #        yield c
#     return cm