Source code for pyscaffold.contrib.configupdater

"""Configuration file updater.

A configuration file consists of sections, lead by a "[section]" header,
and followed by "name: value" entries, with continuations and such in
the style of RFC 822.

The basic idea of ConfigUpdater is that a configuration file consists of
three kinds of building blocks: sections, comments and spaces for separation.
A section itself consists of three kinds of blocks: options, comments and
spaces. This gives us the corresponding data structures to describe a
configuration file.

A general block object contains the lines which were parsed and make up
the block. If a block object was not changed then during writing the same
lines that were parsed will be used to express the block. In case a block,
e.g. an option, was changed, it is marked as `updated` and its values will
be transformed into a corresponding string during an update of a
configuration file.


.. note::

   ConfigUpdater was created by starting from Python's ConfigParser source
   code and changing it according to my needs. Thus this source code
   is subject to the PSF License in a way but I am not a lawyer.
"""

import io
import os
import re
import sys
from abc import ABC
from collections import OrderedDict as _default_dict
from collections.abc import MutableMapping
from configparser import (ConfigParser, DuplicateOptionError,
                          DuplicateSectionError, Error,
                          MissingSectionHeaderError, NoOptionError,
                          NoSectionError, ParsingError)

__all__ = ["NoSectionError", "DuplicateOptionError", "DuplicateSectionError",
           "NoOptionError", "NoConfigFileReadError", "ParsingError",
           "MissingSectionHeaderError", "ConfigUpdater"]


[docs]class NoConfigFileReadError(Error): """Raised when no configuration file was read but update requested.""" def __init__(self): super().__init__( "No configuration file was yet read! Use .read(...) first.")
# Used in parser getters to indicate the default behaviour when a specific # option is not found it to raise an exception. Created to enable 'None' as # a valid fallback value. _UNSET = object() class Container(ABC): """Abstract Mixin Class """ def __init__(self, **kwargs): self._structure = list() super().__init__(**kwargs) @property def structure(self): return self._structure @property def last_item(self): if self._structure: return self._structure[-1] else: return None class Block(ABC): """Abstract Block type holding lines Block objects hold original lines from the configuration file and hold a reference to a container wherein the object resides. """ def __init__(self, container=None, **kwargs): self._container = container self.lines = [] self._updated = False super().__init__(**kwargs) def __str__(self): return ''.join(self.lines) def __len__(self): return len(self.lines) def __eq__(self, other): if isinstance(other, self.__class__): return self.lines == other.lines else: return False def add_line(self, line): """Add a line to the current block Args: line (str): one line to add """ self.lines.append(line) return self @property def container(self): return self._container @property def add_before(self): """Returns a builder inserting a new block before the current block""" idx = self._container.structure.index(self) return BlockBuilder(self._container, idx) @property def add_after(self): """Returns a builder inserting a new block after the current block""" idx = self._container.structure.index(self) return BlockBuilder(self._container, idx+1) class BlockBuilder(object): """Builder that injects blocks at a given index position.""" def __init__(self, container, idx): self._container = container self._idx = idx def comment(self, text, comment_prefix='#'): """Creates a comment block Args: text (str): content of comment without # comment_prefix (str): character indicating start of comment Returns: self for chaining """ comment = Comment(self._container) if not text.startswith(comment_prefix): text = "{} {}".format(comment_prefix, text) if not text.endswith('\n'): text = "{}{}".format(text, '\n') comment.add_line(text) self._container.structure.insert(self._idx, comment) self._idx += 1 return self def section(self, section): """Creates a section block Args: section (str or :class:`Section`): name of section or object Returns: self for chaining """ if not isinstance(self._container, ConfigUpdater): raise ValueError("Sections can only be added at section level!") if isinstance(section, str): # create a new section section = Section(section, container=self._container) elif not isinstance(section, Section): raise ValueError("Parameter must be a string or Section type!") if section.name in [block.name for block in self._container if isinstance(block, Section)]: raise DuplicateSectionError(section.name) self._container.structure.insert(self._idx, section) self._idx += 1 return self def space(self, newlines=1): """Creates a vertical space of newlines Args: newlines (int): number of empty lines Returns: self for chaining """ space = Space() for line in range(newlines): space.add_line('\n') self._container.structure.insert(self._idx, space) self._idx += 1 return self def option(self, key, value=None, **kwargs): """Creates a new option inside a section Args: key (str): key of the option value (str or None): value of the option **kwargs: are passed to the constructor of :class:`Option` Returns: self for chaining """ if not isinstance(self._container, Section): raise ValueError("Options can only be added inside a section!") option = Option(key, value, container=self._container, **kwargs) option.value = value self._container.structure.insert(self._idx, option) self._idx += 1 return self class Comment(Block): """Comment block""" def __init__(self, container=None): super().__init__(container=container) def __repr__(self): return '<Comment>' class Space(Block): """Vertical space block of new lines""" def __init__(self, container=None): super().__init__(container=container) def __repr__(self): return '<Space>' class Section(Block, Container, MutableMapping): """Section block holding options Attributes: name (str): name of the section updated (bool): indicates name change or a new section """ def __init__(self, name, container, **kwargs): self._name = name self._structure = list() self._updated = False super().__init__(container=container, **kwargs) def add_option(self, entry): """Add an Option object to the section Used during initial parsing mainly Args: entry (Option): key value pair as Option object """ self._structure.append(entry) return self def add_comment(self, line): """Add a Comment object to the section Used during initial parsing mainly Args: line (str): one line in the comment """ if not isinstance(self.last_item, Comment): comment = Comment(self._structure) self._structure.append(comment) self.last_item.add_line(line) return self def add_space(self, line): """Add a Space object to the section Used during initial parsing mainly Args: line (str): one line that defines the space, maybe whitespaces """ if not isinstance(self.last_item, Space): space = Space(self._structure) self._structure.append(space) self.last_item.add_line(line) return self def _get_option_idx(self, key): idx = [i for i, entry in enumerate(self._structure) if isinstance(entry, Option) and entry.key == key] if idx: return idx[0] else: raise ValueError def __str__(self): if not self.updated: s = super().__str__() else: s = "[{}]\n".format(self._name) for entry in self._structure: s += str(entry) return s def __repr__(self): return '<Section: {}>'.format(self.name) def __getitem__(self, key): if key not in self.options(): raise KeyError(key) return self._structure[self._get_option_idx(key=key)] def __setitem__(self, key, value): if key in self: option = self.__getitem__(key) option.value = value else: option = Option(key, value, container=self) option.value = value self._structure.append(option) def __delitem__(self, key): if key not in self.options(): raise KeyError(key) idx = self._get_option_idx(key=key) del self._structure[idx] def __contains__(self, key): return key in self.options() def __len__(self): return len(self._structure) def __iter__(self): """Return all entries, not just options""" return self._structure.__iter__() def __eq__(self, other): if isinstance(other, self.__class__): return (self.name == other.name and self._structure == other._structure) else: return False def option_blocks(self): """Returns option blocks Returns: list: list of :class:`Option` blocks """ return [entry for entry in self._structure if isinstance(entry, Option)] def options(self): """Returns option names Returns: list: list of option names as strings """ return [option.key for option in self.option_blocks()] def to_dict(self): """Transform to dictionary Returns: dict: dictionary with same content """ return {key: self.__getitem__(key).value for key in self.options()} @property def updated(self): """Returns if the option was changed/updated""" # if no lines were added, treat it as updated since we added it return self._updated or not self.lines @property def name(self): return self._name @name.setter def name(self, value): self._name = str(value) self._updated = True def set(self, option, value=None): """Set an option for chaining. Args: option (str): option name value (str): value, default None """ option = self._container.optionxform(option) if option in self.options(): self.__getitem__(option).value = value else: self.__setitem__(option, value) return self def insert_at(self, idx): """Returns a builder inserting a new block at the given index Args: idx (int): index where to insert """ return BlockBuilder(self, idx) class Option(Block): """Option block holding a key/value pair. Attributes: key (str): name of the key value (str): stored value updated (bool): indicates name change or a new section """ def __init__(self, key, value, container, delimiter='=', space_around_delimiters=True, line=None): super().__init__(container=container) self._key = key self._values = [value] self._value_is_none = value is None self._delimiter = delimiter self._value = None # will be filled after join_multiline_value self._updated = False self._multiline_value_joined = False self._space_around_delimiters = space_around_delimiters if line: self.lines.append(line) def add_line(self, line): super().add_line(line) self._values.append(line.strip()) def _join_multiline_value(self): if not self._multiline_value_joined and not self._value_is_none: # do what `_join_multiline_value` in ConfigParser would do self._value = '\n'.join(self._values).rstrip() self._multiline_value_joined = True def __str__(self): if not self.updated: return super().__str__() if self._value is None: return "{}{}".format(self._key, '\n') if self._space_around_delimiters: # no space is needed if we use multi-line arguments suffix = '' if str(self._value).startswith('\n') else ' ' delim = " {}{}".format(self._delimiter, suffix) else: delim = self._delimiter return "{}{}{}{}".format(self._key, delim, self._value, '\n') def __repr__(self): return '<Option: {} = {}>'.format(self.key, self.value) @property def updated(self): """Returns if the option was changed/updated""" # if no lines were added, treat it as updated since we added it return self._updated or not self.lines @property def key(self): return self._key @key.setter def key(self, value): self._join_multiline_value() self._key = value self._updated = True @property def value(self): self._join_multiline_value() return self._value @value.setter def value(self, value): self._updated = True self._multiline_value_joined = True self._value = value self._values = [value] def set_values(self, values, separator='\n', indent=4*' '): """Sets the value to a given list of options, e.g. multi-line values Args: values (list): list of values separator (str): separator for values, default: line separator indent (str): indentation depth in case of line separator """ self._updated = True self._multiline_value_joined = True self._values = values if separator == '\n': values.insert(0, '') separator = separator + indent self._value = separator.join(values)
[docs]class ConfigUpdater(Container, MutableMapping): """Parser for updating configuration files. ConfigUpdater follows the API of ConfigParser with some differences: * inline comments are treated as part of a key's value, * only a single config file can be updated at a time, * empty lines in values are not valid, * the original case of sections and keys are kept, * control over the position of a new section/key. Following features are **deliberately not** implemented: * interpolation of values, * propagation of parameters from the default section, * conversions of values, * passing key/value-pairs with ``default`` argument, * non-strict mode allowing duplicate sections and keys. """ # Regular expressions for parsing section headers and options _SECT_TMPL = r""" \[ # [ (?P<header>[^]]+) # very permissive! \] # ] """ _OPT_TMPL = r""" (?P<option>.*?) # very permissive! \s*(?P<vi>{delim})\s* # any number of space/tab, # followed by any of the # allowed delimiters, # followed by any space/tab (?P<value>.*)$ # everything up to eol """ _OPT_NV_TMPL = r""" (?P<option>.*?) # very permissive! \s*(?: # any number of space/tab, (?P<vi>{delim})\s* # optionally followed by # any of the allowed # delimiters, followed by any # space/tab (?P<value>.*))?$ # everything up to eol """ # Compiled regular expression for matching sections SECTCRE = re.compile(_SECT_TMPL, re.VERBOSE) # Compiled regular expression for matching options with typical separators OPTCRE = re.compile(_OPT_TMPL.format(delim="=|:"), re.VERBOSE) # Compiled regular expression for matching options with optional values # delimited using typical separators OPTCRE_NV = re.compile(_OPT_NV_TMPL.format(delim="=|:"), re.VERBOSE) # Compiled regular expression for matching leading whitespace in a line NONSPACECRE = re.compile(r"\S") def __init__(self, allow_no_value=False, *, delimiters=('=', ':'), comment_prefixes=('#', ';'), inline_comment_prefixes=None, strict=True, space_around_delimiters=True): """Constructor of ConfigUpdater Args: allow_no_value (bool): allow keys without a value, default False delimiters (tuple): delimiters for key/value pairs, default =, : comment_prefixes (tuple): prefix of comments, default # and ; inline_comment_prefixes (tuple): prefix of inline comment, default None strict (bool): each section must be unique as well as every key within a section, default True space_around_delimiters (bool): add a space before and after the delimiter, default True """ self._filename = None self._space_around_delimiters = space_around_delimiters self._dict = _default_dict # no reason to let the user change this # keeping _sections to keep code aligned with ConfigParser but # _structure takes the actual role instead. Only use self._structure! self._sections = self._dict() self._structure = [] self._delimiters = tuple(delimiters) if delimiters == ('=', ':'): self._optcre = self.OPTCRE_NV if allow_no_value else self.OPTCRE else: d = "|".join(re.escape(d) for d in delimiters) if allow_no_value: self._optcre = re.compile(self._OPT_NV_TMPL.format(delim=d), re.VERBOSE) else: self._optcre = re.compile(self._OPT_TMPL.format(delim=d), re.VERBOSE) self._comment_prefixes = tuple(comment_prefixes or ()) self._inline_comment_prefixes = tuple(inline_comment_prefixes or ()) self._strict = strict self._allow_no_value = allow_no_value # Options from ConfigParser that we need to set constantly self._empty_lines_in_values = False super().__init__() def _get_section_idx(self, name): idx = [i for i, entry in enumerate(self._structure) if isinstance(entry, Section) and entry.name == name] if idx: return idx[0] else: raise ValueError
[docs] def read(self, filename, encoding=None): """Read and parse a filename. Args: filename (str): path to file encoding (str): encoding of file, default None """ with open(filename, encoding=encoding) as fp: self._read(fp, filename) self._filename = os.path.abspath(filename)
[docs] def read_file(self, f, source=None): """Like read() but the argument must be a file-like object. The ``f`` argument must be iterable, returning one line at a time. Optional second argument is the ``source`` specifying the name of the file being read. If not given, it is taken from f.name. If ``f`` has no ``name`` attribute, ``<???>`` is used. Args: f: file like object source (str): reference name for file object, default None """ if source is None: try: source = f.name except AttributeError: source = '<???>' self._read(f, source)
[docs] def read_string(self, string, source='<string>'): """Read configuration from a given string. Args: string (str): string containing a configuration source (str): reference name for file object, default '<string>' """ sfile = io.StringIO(string) self.read_file(sfile, source)
[docs] def optionxform(self, optionstr): """Converts an option key to lower case for unification Args: optionstr (str): key name Returns: str: unified option name """ return optionstr.lower()
def _update_curr_block(self, block_type): if not isinstance(self.last_item, block_type): new_block = block_type(container=self) self._structure.append(new_block) def _add_comment(self, line): if isinstance(self.last_item, Section): self.last_item.add_comment(line) else: self._update_curr_block(Comment) self.last_item.add_line(line) def _add_section(self, sectname, line): new_section = Section(sectname, container=self) new_section.add_line(line) self._structure.append(new_section) def _add_option(self, key, vi, value, line): entry = Option( key, value, delimiter=vi, container=self.last_item, space_around_delimiters=self._space_around_delimiters, line=line) self.last_item.add_option(entry) def _add_space(self, line): if isinstance(self.last_item, Section): self.last_item.add_space(line) else: self._update_curr_block(Space) self.last_item.add_line(line) def _read(self, fp, fpname): """Parse a sectioned configuration file. Each section in a configuration file contains a header, indicated by a name in square brackets (`[]`), plus key/value options, indicated by `name` and `value` delimited with a specific substring (`=` or `:` by default). Values can span multiple lines, as long as they are indented deeper than the first line of the value. Depending on the parser's mode, blank lines may be treated as parts of multiline values or ignored. Configuration files may include comments, prefixed by specific characters (`#` and `;` by default). Comments may appear on their own in an otherwise empty line or may be entered in lines holding values or section names. Note: This method was borrowed from ConfigParser and we keep this mess here as close as possible to the original messod (pardon this german pun) for consistency reasons and later upgrades. """ self._structure = [] elements_added = set() cursect = None # None, or a dictionary sectname = None optname = None lineno = 0 indent_level = 0 e = None # None, or an exception for lineno, line in enumerate(fp, start=1): comment_start = sys.maxsize # strip inline comments inline_prefixes = {p: -1 for p in self._inline_comment_prefixes} while comment_start == sys.maxsize and inline_prefixes: next_prefixes = {} for prefix, index in inline_prefixes.items(): index = line.find(prefix, index+1) if index == -1: continue next_prefixes[prefix] = index if index == 0 or (index > 0 and line[index-1].isspace()): comment_start = min(comment_start, index) inline_prefixes = next_prefixes # strip full line comments for prefix in self._comment_prefixes: if line.strip().startswith(prefix): comment_start = 0 self._add_comment(line) # HOOK break if comment_start == sys.maxsize: comment_start = None value = line[:comment_start].strip() if not value: if self._empty_lines_in_values: # add empty line to the value, but only if there was no # comment on the line if (comment_start is None and cursect is not None and optname and cursect[optname] is not None): cursect[optname].append('') # newlines added at join self.last_item.last_item.add_line(line) # HOOK else: # empty line marks end of value indent_level = sys.maxsize if comment_start is None: self._add_space(line) continue # continuation line? first_nonspace = self.NONSPACECRE.search(line) cur_indent_level = first_nonspace.start() if first_nonspace else 0 if (cursect is not None and optname and cur_indent_level > indent_level): cursect[optname].append(value) self.last_item.last_item.add_line(line) # HOOK # a section header or option header? else: indent_level = cur_indent_level # is it a section header? mo = self.SECTCRE.match(value) if mo: sectname = mo.group('header') if sectname in self._sections: if self._strict and sectname in elements_added: raise DuplicateSectionError(sectname, fpname, lineno) cursect = self._sections[sectname] elements_added.add(sectname) else: cursect = self._dict() self._sections[sectname] = cursect elements_added.add(sectname) # So sections can't start with a continuation line optname = None self._add_section(sectname, line) # HOOK # no section header in the file? elif cursect is None: raise MissingSectionHeaderError(fpname, lineno, line) # an option line? else: mo = self._optcre.match(value) if mo: optname, vi, optval = mo.group('option', 'vi', 'value') if not optname: e = self._handle_error(e, fpname, lineno, line) optname = self.optionxform(optname.rstrip()) if (self._strict and (sectname, optname) in elements_added): raise DuplicateOptionError(sectname, optname, fpname, lineno) elements_added.add((sectname, optname)) # This check is fine because the OPTCRE cannot # match if it would set optval to None if optval is not None: optval = optval.strip() cursect[optname] = [optval] else: # valueless option handling cursect[optname] = None self._add_option(optname, vi, optval, line) # HOOK else: # a non-fatal parsing error occurred. set up the # exception but keep going. the exception will be # raised at the end of the file and will contain a # list of all bogus lines e = self._handle_error(e, fpname, lineno, line) # if any parsing errors occurred, raise an exception if e: raise e def _handle_error(self, exc, fpname, lineno, line): if not exc: exc = ParsingError(fpname) exc.append(lineno, repr(line)) return exc
[docs] def write(self, fp): """Write an .ini-format representation of the configuration state. Args: fp (file-like object): open file handle """ fp.write(str(self))
[docs] def update_file(self): """Update the read-in configuration file. """ if self._filename is None: raise NoConfigFileReadError() with open(self._filename, 'w') as fb: self.write(fb)
[docs] def validate_format(self, **kwargs): """Call ConfigParser to validate config Args: kwargs: are passed to :class:`configparser.ConfigParser` """ args = dict( dict_type=self._dict, allow_no_value=self._allow_no_value, inline_comment_prefixes=self._inline_comment_prefixes, strict=self._strict, empty_lines_in_values=self._empty_lines_in_values ) args.update(kwargs) parser = ConfigParser(**args) updated_cfg = str(self) parser.read_string(updated_cfg)
[docs] def sections_blocks(self): """Returns all section blocks Returns: list: list of :class:`Section` blocks """ return [block for block in self._structure if isinstance(block, Section)]
[docs] def sections(self): """Return a list of section names Returns: list: list of section names """ return [section.name for section in self.sections_blocks()]
def __str__(self): return ''.join(str(block) for block in self._structure) def __getitem__(self, key): for section in self.sections_blocks(): if section.name == key: return section else: raise KeyError(key) def __setitem__(self, key, value): if not isinstance(value, Section): raise ValueError("Value must be of type Section!") if isinstance(key, str) and key in self: idx = self._get_section_idx(key) del self._structure[idx] self._structure.insert(idx, value) else: # name the section by the key value.name = key self.add_section(value) def __delitem__(self, section): if not self.has_section(section): raise KeyError(section) self.remove_section(section) def __contains__(self, key): return self.has_section(key) def __len__(self): """Number of all blocks, not just sections""" return len(self._structure) def __iter__(self): """Iterate over all blocks, not just sections""" return self._structure.__iter__() def __eq__(self, other): if isinstance(other, self.__class__): return self._structure == other._structure else: return False
[docs] def add_section(self, section): """Create a new section in the configuration. Raise DuplicateSectionError if a section by the specified name already exists. Raise ValueError if name is DEFAULT. Args: section (str or :class:`Section`): name or Section type """ if section in self.sections(): raise DuplicateSectionError(section) if isinstance(section, str): # create a new section section = Section(section, container=self) elif not isinstance(section, Section): raise ValueError("Parameter must be a string or Section type!") self._structure.append(section)
[docs] def has_section(self, section): """Returns whether the given section exists. Args: section (str): name of section Returns: bool: wether the section exists """ return section in self.sections()
[docs] def options(self, section): """Returns list of configuration options for the named section. Args: section (str): name of section Returns: list: list of option names """ if not self.has_section(section): raise NoSectionError(section) from None return self.__getitem__(section).options()
[docs] def get(self, section, option): """Gets an option value for a given section. Args: section (str): section name option (str): option name Returns: :class:`Option`: Option object holding key/value pair """ if not self.has_section(section): raise NoSectionError(section) from None section = self.__getitem__(section) option = self.optionxform(option) try: value = section[option] except KeyError: raise NoOptionError(option, section) return value
[docs] def items(self, section=_UNSET): """Return a list of (name, value) tuples for options or sections. If section is given, return a list of tuples with (name, value) for each option in the section. Otherwise, return a list of tuples with (section_name, section_type) for each section. Args: section (str): optional section name, default UNSET Returns: list: list of :class:`Section` or :class:`Option` objects """ if section is _UNSET: return [(sect.name, sect) for sect in self.sections_blocks()] section = self.__getitem__(section) return [(opt.key, opt) for opt in section.option_blocks()]
[docs] def has_option(self, section, option): """Checks for the existence of a given option in a given section. Args: section (str): name of section option (str): name of option Returns: bool: whether the option exists in the given section """ if section not in self.sections(): return False else: option = self.optionxform(option) return option in self[section]
[docs] def set(self, section, option, value=None): """Set an option. Args: section (str): section name option (str): option name value (str): value, default None """ try: section = self.__getitem__(section) except KeyError: raise NoSectionError(section) from None option = self.optionxform(option) if option in section: section[option].value = value else: section[option] = value return self
[docs] def remove_option(self, section, option): """Remove an option. Args: section (str): section name option (str): option name Returns: bool: whether the option was actually removed """ try: section = self.__getitem__(section) except KeyError: raise NoSectionError(section) from None option = self.optionxform(option) existed = option in section.options() if existed: del section[option] return existed
[docs] def remove_section(self, name): """Remove a file section. Args: name: name of the section Returns: bool: whether the section was actually removed """ existed = self.has_section(name) if existed: idx = self._get_section_idx(name) del self._structure[idx] return existed
[docs] def to_dict(self): """Transform to dictionary Returns: dict: dictionary with same content """ return {sect: self.__getitem__(sect).to_dict() for sect in self.sections()}