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chore: add typing to cloudinit.distros.parsers hostname and resolv_conf #6848

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chore: add typing to cloudinit.distros.parsers hostname and resolv_conf #6848

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ea32a8f
chore: add typing to cloudinit.distros.parsers hostname and resolv_conf
Ahmedaltu Apr 21, 2026
4bea5da
fix: use _parsed flag instead of assert for type narrowing
Ahmedaltu Apr 21, 2026
351ed84
fix: revert unnecessary variable rename in __str__
Ahmedaltu Apr 21, 2026
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27 changes: 15 additions & 12 deletions cloudinit/distros/parsers/hostname.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,21 +5,24 @@
# This file is part of cloud-init. See LICENSE file for license information.

from io import StringIO
from typing import List, Optional, Tuple

from cloudinit.distros.parsers import chop_comment


# Parser that knows how to work with /etc/hostname format
class HostnameConf:
def __init__(self, text):
def __init__(self, text: str) -> None:
self._text = text
self._contents = None
self._parsed: bool = False
self._contents: List[Tuple[str, List[str]]] = []

def parse(self):
if self._contents is None:
def parse(self) -> None:
if not self._parsed:
self._contents = self._parse(self._text)
self._parsed = True

def __str__(self):
def __str__(self) -> str:
self.parse()
contents = StringIO()
for line_type, components in self._contents:
Expand All @@ -31,20 +34,20 @@ def __str__(self):
(hostname, tail) = components
contents.write("%s%s\n" % (hostname, tail))
# Ensure trailing newline
contents = contents.getvalue()
if not contents.endswith("\n"):
contents += "\n"
return contents
rendered = contents.getvalue()
if not rendered.endswith("\n"):
rendered += "\n"
return rendered

@property
def hostname(self):
def hostname(self) -> Optional[str]:
self.parse()
for line_type, components in self._contents:
if line_type == "hostname":
return components[0]
return None

def set_hostname(self, your_hostname):
def set_hostname(self, your_hostname: str) -> None:
your_hostname = your_hostname.strip()
if not your_hostname:
return
Expand All @@ -57,7 +60,7 @@ def set_hostname(self, your_hostname):
if not replaced:
self._contents.append(("hostname", [str(your_hostname), ""]))

def _parse(self, contents):
def _parse(self, contents: str) -> List[Tuple[str, List[str]]]:
entries = []
hostnames_found = set()
for line in contents.splitlines():
Expand Down
32 changes: 17 additions & 15 deletions cloudinit/distros/parsers/resolv_conf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@

import logging
from io import StringIO
from typing import List, Optional, Tuple

from cloudinit import util
from cloudinit.distros.parsers import chop_comment
Expand All @@ -15,36 +16,37 @@

# See: man resolv.conf
class ResolvConf:
def __init__(self, text):
def __init__(self, text: str) -> None:
self._text = text
self._contents = None
self._parsed: bool = False
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@holmanb holmanb Apr 21, 2026

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This new variable seems unnecessary and error-prone. It should be possible to simply check the truthy value of self._contents rather than manually using a boolean to track the same thing.

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@Ahmedaltu Ahmedaltu Apr 21, 2026

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Hi @holmanb, I considered using if not self._contents but there's a subtle issue — when the input text is empty or contains only comments, _parse() returns an empty list []. Since an empty list is falsy, using if not self._contents would cause parse() to re-run on every call for empty files, defeating the lazy-parse caching.

The _parsed flag correctly distinguishes between "not yet parsed" and "parsed but empty result". This is the same reason network_state.py uses a dedicated _parsed boolean rather than checking the contents directly.

Happy to use a different approach if you have a preferred solution for this case.

self._contents: List[Tuple[str, List[str]]] = []

def parse(self):
if self._contents is None:
def parse(self) -> None:
if not self._parsed:
self._contents = self._parse(self._text)
self._parsed = True

@property
def nameservers(self):
def nameservers(self) -> List[str]:
self.parse()
return self._retr_option("nameserver")

@property
def local_domain(self):
def local_domain(self) -> Optional[str]:
self.parse()
dm = self._retr_option("domain")
if dm:
return dm[0]
return None

@local_domain.setter
def local_domain(self, domain):
def local_domain(self, domain: str) -> None:
self.parse()
self._remove_option("domain")
self._contents.append(("option", ["domain", str(domain), ""]))
return domain

@property
def search_domains(self):
def search_domains(self) -> List[str]:
self.parse()
current_sds = self._retr_option("search")
flat_sds = []
Expand All @@ -54,7 +56,7 @@ def search_domains(self):
flat_sds.append(sd)
return flat_sds

def __str__(self):
def __str__(self) -> str:
self.parse()
contents = StringIO()
for line_type, components in self._contents:
Expand All @@ -70,7 +72,7 @@ def __str__(self):
contents.write("%s\n" % (line))
return contents.getvalue()

def _retr_option(self, opt_name):
def _retr_option(self, opt_name: str) -> List[str]:
found = []
for line_type, components in self._contents:
if line_type == "option":
Expand All @@ -79,7 +81,7 @@ def _retr_option(self, opt_name):
found.append(cfg_value)
return found

def add_nameserver(self, ns):
def add_nameserver(self, ns: str) -> List[str]:
self.parse()
current_ns = self._retr_option("nameserver")
new_ns = list(current_ns)
Expand All @@ -92,7 +94,7 @@ def add_nameserver(self, ns):
self._contents.append(("option", ["nameserver", n, ""]))
return new_ns

def _remove_option(self, opt_name):
def _remove_option(self, opt_name: str) -> None:
def remove_opt(item):
line_type, components = item
if line_type != "option":
Expand All @@ -108,7 +110,7 @@ def remove_opt(item):
new_contents.append(c)
self._contents = new_contents

def add_search_domain(self, search_domain):
def add_search_domain(self, search_domain: str) -> List[str]:
flat_sds = self.search_domains
new_sds = list(flat_sds)
new_sds.append(str(search_domain))
Expand All @@ -132,7 +134,7 @@ def add_search_domain(self, search_domain):
self._contents.append(("option", ["search", s_list, ""]))
return flat_sds

def _parse(self, contents):
def _parse(self, contents: str) -> List[Tuple[str, List[str]]]:
entries = []
for i, line in enumerate(contents.splitlines()):
sline = line.strip()
Expand Down
2 changes: 0 additions & 2 deletions pyproject.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -54,9 +54,7 @@ module = [
"cloudinit.distros.azurelinux",
"cloudinit.distros.bsd",
"cloudinit.distros.opensuse",
"cloudinit.distros.parsers.hostname",
"cloudinit.distros.parsers.hosts",
"cloudinit.distros.parsers.resolv_conf",
"cloudinit.distros.ug_util",
"cloudinit.helpers",
"cloudinit.net.cmdline",
Expand Down
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