From 1325ca4baadd581d2ed67fc83cbe71e80ef70569 Mon Sep 17 00:00:00 2001
From: "d.kovalenko" <dmitry.lipetsk@gmail.com>
Date: Sun, 2 Nov 2025 15:19:49 +0300
Subject: [PATCH] ConfigurationFileReader::ReadLine returns
 typing.Optional[str]

It returns str or None

None - it is EOF.
---
 src/implementation/v00/configuration_base.py |  2 +-
 src/os/abstract/configuration_os_ops.py      |  3 ++-
 src/os/local/configuration_os_ops.py         | 12 ++++++++++--
 tests/CfgFileReader.py                       | 13 +++++++++++--
 4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/implementation/v00/configuration_base.py b/src/implementation/v00/configuration_base.py
index 19b11e9..361876d 100644
--- a/src/implementation/v00/configuration_base.py
+++ b/src/implementation/v00/configuration_base.py
@@ -3308,7 +3308,7 @@ def Helper__LoadFileContent(
             lineData = fileContent.ReadLine()
 
             if not lineData:
-                # assert lineData is None
+                assert lineData is None
                 break
 
             assert type(lineData) == str
diff --git a/src/os/abstract/configuration_os_ops.py b/src/os/abstract/configuration_os_ops.py
index 3d4bde1..209db11 100644
--- a/src/os/abstract/configuration_os_ops.py
+++ b/src/os/abstract/configuration_os_ops.py
@@ -6,6 +6,7 @@
 from ...core.raise_error import RaiseError
 
 import datetime
+import typing
 
 
 # //////////////////////////////////////////////////////////////////////////////
@@ -13,7 +14,7 @@
 
 
 class ConfigurationFileReader:
-    def ReadLine(self) -> str:
+    def ReadLine(self) -> typing.Optional[str]:
         RaiseError.MethodIsNotImplemented(__class__, "ReadLine")
 
 
diff --git a/src/os/local/configuration_os_ops.py b/src/os/local/configuration_os_ops.py
index c73fac6..03e3620 100644
--- a/src/os/local/configuration_os_ops.py
+++ b/src/os/local/configuration_os_ops.py
@@ -8,6 +8,7 @@
 import os
 import io
 import datetime
+import typing
 
 # //////////////////////////////////////////////////////////////////////////////
 # class ConfigurationOsFile
@@ -49,9 +50,16 @@ def IsClosed(self) -> bool:
         return self.m_file is None
 
     # --------------------------------------------------------------------
-    def ReadLine(self) -> str:
+    def ReadLine(self) -> typing.Optional[str]:
         assert isinstance(self.m_file, io.TextIOWrapper)
-        return self.m_file.readline()
+        r = self.m_file.readline()
+        assert type(r) == str  # noqa: E721
+        if not r:
+            assert r == ""
+            return None
+
+        assert r != ""
+        return r
 
     # --------------------------------------------------------------------
     def Overwrite(self, text: str) -> None:
diff --git a/tests/CfgFileReader.py b/tests/CfgFileReader.py
index 1f80f31..52691e5 100644
--- a/tests/CfgFileReader.py
+++ b/tests/CfgFileReader.py
@@ -4,6 +4,7 @@
 from src.os.abstract.configuration_os_ops import ConfigurationFileReader
 
 import io
+import typing
 
 # //////////////////////////////////////////////////////////////////////////////
 # class CfgFileReader
@@ -19,9 +20,17 @@ def __init__(self, text: str):
         self.m_file = io.StringIO(text)
 
     # --------------------------------------------------------------------
-    def ReadLine(self) -> str:
+    def ReadLine(self) -> typing.Optional[str]:
         assert type(self.m_file) == io.StringIO
-        return self.m_file.readline()
+
+        r = self.m_file.readline()
+        assert type(r) == str  # noqa: E721
+        if not r:
+            assert r == ""
+            return None
+
+        assert r != ""
+        return r
 
 
 # //////////////////////////////////////////////////////////////////////////////