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#!/usr/bin/python3
#
# Copyright (C) Canonical Ltd
#
# SPDX-License-Identifier: GPL-2.0+
"""deb822 parser with support for comment headers and footers."""
import collections
import io
import typing
import apt_pkg
T = typing.TypeVar("T")
class Section:
"""A single deb822 section, possibly with comments.
This represents a single deb822 section.
"""
tags: collections.OrderedDict[str, str]
_case_mapping: dict[str, str]
header: str
footer: str
def __init__(self, section: typing.Union[str, "Section"]):
if isinstance(section, Section):
self.tags = collections.OrderedDict(section.tags)
self._case_mapping = {k.casefold(): k for k in self.tags}
self.header = section.header
self.footer = section.footer
return
comments = ["", ""]
in_section = False
trimmed_section = ""
for line in section.split("\n"):
if line.startswith("#"):
# remove the leading #
line = line[1:]
comments[in_section] += line + "\n"
continue
in_section = True
trimmed_section += line + "\n"
self.tags = collections.OrderedDict(apt_pkg.TagSection(trimmed_section))
self._case_mapping = {k.casefold(): k for k in self.tags}
self.header, self.footer = comments
def __getitem__(self, key: str) -> str:
"""Get the value of a field."""
return self.tags[self._case_mapping.get(key.casefold(), key)]
def __delitem__(self, key: str) -> None:
"""Delete a field"""
del self.tags[self._case_mapping.get(key.casefold(), key)]
def __setitem__(self, key: str, val: str) -> None:
"""Set the value of a field."""
if key.casefold() not in self._case_mapping:
self._case_mapping[key.casefold()] = key
self.tags[self._case_mapping[key.casefold()]] = val
def __bool__(self) -> bool:
return bool(self.tags)
@typing.overload
def get(self, key: str) -> str | None: ...
@typing.overload
def get(self, key: str, default: T) -> T | str: ...
def get(self, key: str, default: T | None = None) -> T | None | str:
try:
return self[key]
except KeyError:
return default
@staticmethod
def __comment_lines(content: str) -> str:
return (
"\n".join("#" + line for line in content.splitlines()) + "\n"
if content
else ""
)
def __str__(self) -> str:
"""Canonical string rendering of this section."""
return (
self.__comment_lines(self.header)
+ "".join(f"{k}: {v}\n" for k, v in self.tags.items())
+ self.__comment_lines(self.footer)
)
class File:
"""
Parse a given file object into a list of Section objects.
"""
def __init__(self, fobj: io.TextIOBase):
self.sections = []
section = ""
for line in fobj:
if not line.isspace():
# A line is part of the section if it has non-whitespace characters
section += line
elif section:
# Our line is just whitespace and we have gathered section content, so let's write out the section
self.sections.append(Section(section))
section = ""
# The final section may not be terminated by an empty line
if section:
self.sections.append(Section(section))
def __iter__(self) -> typing.Iterator[Section]:
return iter(self.sections)
def __str__(self) -> str:
return "\n".join(str(s) for s in self.sections)
if __name__ == "__main__":
st = """# Header
# More header
K1: V1
# Inline
K2: V2
# not a comment
# Footer
# More footer
"""
s = Section(st)
print(s)
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