standardize config on ruamel.yaml with a YAML 1.2 config

This is a key piece of the ongoing `PUBLISH` _config.yml_ migration. There was uneven implementation of which YAML parser to use, and that could lead to bugs where one parser might read a value one way, and a different parser will read the value a different way. I wanted to be sure that YAML 1.2 would always work.

This makes all code that handles config files use the same `ruamel.yaml` parsers.  This only touches other usages of YAML parsers when there is overlap.  This does not port all of _fdroidserver_ to `ruamel.yaml` and YAML 1.2.  The metadata files should already be YAML 1.2 anyway.

# Conflicts:
#	fdroidserver/lint.py

fdroidserver/_yaml.py

@@ -0,0 +1,40 @@
+# Copyright (C) 2025, Hans-Christoph Steiner <hans@eds.org>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Standard YAML parsing and dumping.
+
+YAML 1.2 is the preferred format for all data files.  When loading
+F-Droid formats like config.yml and <Application ID>.yml, YAML 1.2 is
+forced, and older YAML constructs should be considered an error.
+
+It is OK to load and dump files in other YAML versions if they are
+externally defined formats, like FUNDING.yml.  In those cases, these
+common instances might not be appropriate to use.
+
+There is a separate instance for dumping based on the "round trip" aka
+"rt" mode.  The "rt" mode maintains order while the "safe" mode sorts
+the output.  Also, yaml.version is not forced in the dumper because that
+makes it write out a "%YAML 1.2" header.  F-Droid's formats are
+explicitly defined as YAML 1.2 and meant to be human-editable.  So that
+header gets in the way.
+
+"""
+
+import ruamel.yaml
+
+yaml = ruamel.yaml.YAML(typ='safe')
+yaml.version = (1, 2)
+
+yaml_dumper = ruamel.yaml.YAML(typ='rt')

fdroidserver/common.py

@@ -39,6 +39,7 @@ import sys
 import re
 import ast
 import gzip
+import ruamel.yaml
 import shutil
 import stat
 import subprocess
@@ -48,7 +49,6 @@ import logging
 import hashlib
 import socket
 import base64
-import yaml
 import zipfile
 import tempfile
 import json
@@ -67,6 +67,7 @@ from zipfile import ZipFile
 
 import fdroidserver.metadata
 from fdroidserver import _
+from fdroidserver._yaml import yaml, yaml_dumper
 from fdroidserver.exception import FDroidException, VCSException, NoSubmodulesException, \
     BuildException, VerificationException, MetaDataException
 from .asynchronousfilereader import AsynchronousFileReader
@@ -549,7 +550,7 @@ def read_config():
     if os.path.exists(CONFIG_FILE):
         logging.debug(_("Reading '{config_file}'").format(config_file=CONFIG_FILE))
         with open(CONFIG_FILE, encoding='utf-8') as fp:
-            config = yaml.safe_load(fp)
+            config = yaml.load(fp)
         if not config:
             config = {}
         config_type_check(CONFIG_FILE, config)
@@ -706,7 +707,7 @@ def load_localized_config(name, repodir):
         if len(f.parts) == 2:
             locale = DEFAULT_LOCALE
         with open(f, encoding="utf-8") as fp:
-            elem = yaml.safe_load(fp)
+            elem = yaml.load(fp)
             if not isinstance(elem, dict):
                 msg = _('{path} is not "key: value" dict, but a {datatype}!')
                 raise TypeError(msg.format(path=f, datatype=type(elem).__name__))
@@ -4229,7 +4230,9 @@ def write_to_config(thisconfig, key, value=None):
             lines[-1] += '\n'
 
     pattern = re.compile(r'^[\s#]*' + key + r':.*\n')
-    repl = yaml.dump({key: value})
+    with ruamel.yaml.compat.StringIO() as fp:
+        yaml_dumper.dump({key: value}, fp)
+        repl = fp.getvalue()
 
     # If we replaced this line once, we make sure won't be a
     # second instance of this line for this key in the document.

fdroidserver/index.py

@@ -26,7 +26,6 @@ import json
 import logging
 import os
 import re
-import ruamel.yaml
 import shutil
 import sys
 import tempfile
@@ -45,6 +44,7 @@ from . import metadata
 from . import net
 from . import signindex
 from fdroidserver.common import ANTIFEATURES_CONFIG_NAME, CATEGORIES_CONFIG_NAME, CONFIG_CONFIG_NAME, MIRRORS_CONFIG_NAME, RELEASECHANNELS_CONFIG_NAME, DEFAULT_LOCALE, FDroidPopen, FDroidPopenBytes, load_stats_fdroid_signing_key_fingerprints
+from fdroidserver._yaml import yaml
 from fdroidserver.exception import FDroidException, VerificationException
 
 
@@ -1445,7 +1445,7 @@ def add_mirrors_to_repodict(repo_section, repodict):
                 )
             )
         with mirrors_yml.open() as fp:
-            mirrors_config = ruamel.yaml.YAML(typ='safe').load(fp)
+            mirrors_config = yaml.load(fp)
         if not isinstance(mirrors_config, list):
             msg = _('{path} is not list, but a {datatype}!')
             raise TypeError(

fdroidserver/lint.py

@@ -24,9 +24,8 @@ import urllib.parse
 from argparse import ArgumentParser
 from pathlib import Path
 
-import ruamel.yaml
-
 from . import _, common, metadata, rewritemeta
+from fdroidserver._yaml import yaml
 
 config = None
 
@@ -853,7 +852,7 @@ def lint_config(arg):
         passed = False
 
     with path.open() as fp:
-        data = ruamel.yaml.YAML(typ='safe').load(fp)
+        data = yaml.load(fp)
     common.config_type_check(arg, data)
 
     if path.name == mirrors_name:

fdroidserver/metadata.py

@@ -31,6 +31,7 @@ from collections import OrderedDict
 from . import common
 from . import _
 from .exception import MetaDataException
+from ._yaml import yaml
 
 srclibs = None
 warnings_action = None
@@ -472,7 +473,6 @@ def parse_yaml_srclib(metadatapath):
 
     with metadatapath.open("r", encoding="utf-8") as f:
         try:
-            yaml = ruamel.yaml.YAML(typ='safe')
             data = yaml.load(f)
             if type(data) is not dict:
                 if platform.system() == 'Windows':
@@ -709,8 +709,7 @@ def parse_yaml_metadata(mf):
 
     """
     try:
-        yaml = ruamel.yaml.YAML(typ='safe')
-        yamldata = yaml.load(mf)
+        yamldata = common.yaml.load(mf)
     except ruamel.yaml.YAMLError as e:
         _warn_or_exception(
             _("could not parse '{path}'").format(path=mf.name)
@@ -1249,19 +1248,24 @@ def _app_to_yaml(app):
 def write_yaml(mf, app):
     """Write metadata in yaml format.
 
+    This requires the 'rt' round trip dumper to maintain order and needs
+    custom indent settings, so it needs to instantiate its own YAML
+    instance.  Therefore, this function deliberately avoids using any of
+    the common YAML parser setups.
+
     Parameters
     ----------
     mf
       active file discriptor for writing
     app
-      app metadata to written to the yaml file
+      app metadata to written to the YAML file
 
     """
     _del_duplicated_NoSourceSince(app)
     yaml_app = _app_to_yaml(app)
-    yaml = ruamel.yaml.YAML()
-    yaml.indent(mapping=2, sequence=4, offset=2)
-    yaml.dump(yaml_app, stream=mf)
+    yamlmf = ruamel.yaml.YAML(typ='rt')
+    yamlmf.indent(mapping=2, sequence=4, offset=2)
+    yamlmf.dump(yaml_app, stream=mf)
 
 
 def write_metadata(metadatapath, app):