Make _compat_skip_empty_lines a per-instance attribute

iniparse/ini.py

@@ -355,7 +355,10 @@ class INISection(config.ConfigNamespace):
     _defaults: Optional["INISection"] = None
     _optionxformvalue: "INIConfig" = None
     _optionxformsource: "INIConfig" = None
-    _compat_skip_empty_lines: Set[str] = set()
+    # The real set is created per instance in __init__().  The immutable
+    # class-level value only makes ConfigNamespace.__setattr__ treat the
+    # name as a member; a mutable set here would be shared by all sections.
+    _compat_skip_empty_lines: Set[str] = frozenset()  # type: ignore[assignment]
 
     def __init__(
         self,
@@ -369,6 +372,7 @@ def __init__(
         self._optionxformvalue = optionxformvalue
         self._optionxformsource = optionxformsource
         self._options = {}
+        self._compat_skip_empty_lines = set()
 
     _optionxform = _make_xform_property('_optionxform')
 

tests/test_regressions.py

@@ -0,0 +1,53 @@
+"""
+:component: python-iniparse
+:requirement: RHSS-291606
+:polarion-project-id: RHELSS
+:polarion-include-skipped: false
+:polarion-lookup-method: id
+:poolteam: rhel-sst-csi-client-tools
+:caseautomation: Automated
+:upstream: No
+"""
+
+import unittest
+from io import StringIO
+
+from iniparse import compat
+
+
+class TestCompatSkipEmptyLines(unittest.TestCase):
+    def test_not_shared_between_instances(self):
+        """
+        :id: fce0ac15-8871-4af4-8017-5f37cbc905b0
+        :title: Empty-line skipping state is not shared between parsers
+        :description:
+            Verifies that the per-option "skip empty lines" compatibility
+            state of one parser is not modified by operations performed
+            on another, unrelated parser.
+        :tags: Tier 1
+        :steps:
+            1. Parse a multi-line value containing an empty line with parser A.
+            2. Set an option with the same name in parser B.
+            3. Set a multi-line value in parser C, then parse a file with
+               parser D that has a same-named multi-line option.
+        :expectedresults:
+            1. Parser A returns the value without the empty line.
+            2. Parser A still returns the value without the empty line.
+            3. Parser C still returns its value with the empty line kept.
+        """
+        a = compat.RawConfigParser()
+        a.readfp(StringIO('[a]\nfoo = line1\n\n  line2\n'))
+        self.assertEqual(a.get('a', 'foo'), 'line1\nline2')
+
+        b = compat.RawConfigParser()
+        b.add_section('b')
+        b.set('b', 'foo', 'x')
+        self.assertEqual(a.get('a', 'foo'), 'line1\nline2')
+
+        c = compat.RawConfigParser()
+        c.add_section('c')
+        c.set('c', 'bar', 'x\n\ny')
+        d = compat.RawConfigParser()
+        d.readfp(StringIO('[d]\nbar = 1\n\n  2\n'))
+        self.assertEqual(c.get('c', 'bar'), 'x\n\ny')
+        self.assertEqual(d.get('d', 'bar'), '1\n2')