From 7f85aeab6419cff32d2eed5ae488354ec747d3c2 Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Fri, 7 Mar 2025 17:48:11 +0300
Subject: [PATCH 1/2] gh-130941: Fix `configparser` parsing values with
 `allow_no_value` and `interpolation`

---
 Lib/configparser.py                              |  2 ++
 Lib/test/test_configparser.py                    | 16 ++++++++++++++++
 ...025-03-07-17-47-32.gh-issue-130941.7_GvhW.rst |  2 ++
 3 files changed, 20 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2025-03-07-17-47-32.gh-issue-130941.7_GvhW.rst

diff --git a/Lib/configparser.py b/Lib/configparser.py
index 70cc651edabd86..6bc920661a2203 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -541,6 +541,8 @@ def _interpolate_some(self, parser, option, accum, rest, section, map,
                 except (KeyError, NoSectionError, NoOptionError):
                     raise InterpolationMissingOptionError(
                         option, section, rawval, ":".join(path)) from None
+                if not v:
+                    continue
                 if "$" in v:
                     self._interpolate_some(parser, opt, accum, v, sect,
                                            dict(parser.items(sect, raw=True)),
diff --git a/Lib/test/test_configparser.py b/Lib/test/test_configparser.py
index 1313ec2b9e884e..468da9bd749434 100644
--- a/Lib/test/test_configparser.py
+++ b/Lib/test/test_configparser.py
@@ -1328,6 +1328,22 @@ class ConfigParserTestCaseNoValue(ConfigParserTestCase):
     allow_no_value = True
 
 
+class ConfigParserTestCaseNoValueAndInterpolation(ConfigParserTestCase):
+    allow_no_value = True
+    interpolation = configparser.ExtendedInterpolation()
+
+    def test_interpolation_with_allow_no_value(self):
+        config = textwrap.dedent("""
+            [dummy]
+            a
+            b = ${a}
+        """)
+        cf = self.fromstring(config)
+
+        self.assertIs(cf["dummy"]["a"], None)
+        self.assertEqual(cf["dummy"]["b"], "")
+
+
 class ConfigParserTestCaseTrickyFile(CfgParserTestCaseClass, unittest.TestCase):
     config_class = configparser.ConfigParser
     delimiters = {'='}
diff --git a/Misc/NEWS.d/next/Library/2025-03-07-17-47-32.gh-issue-130941.7_GvhW.rst b/Misc/NEWS.d/next/Library/2025-03-07-17-47-32.gh-issue-130941.7_GvhW.rst
new file mode 100644
index 00000000000000..4f0cda8d03e902
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-03-07-17-47-32.gh-issue-130941.7_GvhW.rst
@@ -0,0 +1,2 @@
+Fix :class:`configparser.ConfigParser` parsing empty interpolation with
+``allow_no_value`` set to ``True``.

From 1621a0f0e8bbe4b38229ee502b4e863266a5adf2 Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Fri, 7 Mar 2025 18:08:40 +0300
Subject: [PATCH 2/2] Fix CI

---
 Lib/configparser.py           |  2 +-
 Lib/test/test_configparser.py | 29 +++++++++++++++++++++++++++--
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/Lib/configparser.py b/Lib/configparser.py
index 6bc920661a2203..239fda60a02ca0 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -541,7 +541,7 @@ def _interpolate_some(self, parser, option, accum, rest, section, map,
                 except (KeyError, NoSectionError, NoOptionError):
                     raise InterpolationMissingOptionError(
                         option, section, rawval, ":".join(path)) from None
-                if not v:
+                if v is None:
                     continue
                 if "$" in v:
                     self._interpolate_some(parser, opt, accum, v, sect,
diff --git a/Lib/test/test_configparser.py b/Lib/test/test_configparser.py
index 468da9bd749434..23904d17d326d8 100644
--- a/Lib/test/test_configparser.py
+++ b/Lib/test/test_configparser.py
@@ -1328,9 +1328,9 @@ class ConfigParserTestCaseNoValue(ConfigParserTestCase):
     allow_no_value = True
 
 
-class ConfigParserTestCaseNoValueAndInterpolation(ConfigParserTestCase):
-    allow_no_value = True
+class NoValueAndExtendedInterpolation(CfgParserTestCaseClass):
     interpolation = configparser.ExtendedInterpolation()
+    allow_no_value = True
 
     def test_interpolation_with_allow_no_value(self):
         config = textwrap.dedent("""
@@ -1343,6 +1343,31 @@ def test_interpolation_with_allow_no_value(self):
         self.assertIs(cf["dummy"]["a"], None)
         self.assertEqual(cf["dummy"]["b"], "")
 
+    def test_explicit_none(self):
+        config = textwrap.dedent("""
+            [dummy]
+            a = None
+            b = ${a}
+        """)
+        cf = self.fromstring(config)
+
+        self.assertEqual(cf["dummy"]["a"], "None")
+        self.assertEqual(cf["dummy"]["b"], "None")
+
+
+class ConfigParserNoValueAndExtendedInterpolationTest(
+    NoValueAndExtendedInterpolation,
+    unittest.TestCase,
+):
+    config_class = configparser.ConfigParser
+
+
+class RawConfigParserNoValueAndExtendedInterpolationTest(
+    NoValueAndExtendedInterpolation,
+    unittest.TestCase,
+):
+    config_class = configparser.RawConfigParser
+
 
 class ConfigParserTestCaseTrickyFile(CfgParserTestCaseClass, unittest.TestCase):
     config_class = configparser.ConfigParser