Add more robust error handling for SanitizeAndNormalize

- Check return value of second NormalizeString call
- Add check for empty normalized result after processing
- Return sanitized input if normalized result is empty

Co-authored-by: moooyo <42196638+moooyo@users.noreply.github.com>

src/modules/powerrename/lib/PowerRenameRegEx.cpp

@@ -39,10 +39,23 @@ static std::wstring SanitizeAndNormalize(const std::wstring& input)
         return sanitized; // Return unaltered if normalization fails.
     }
 
+    // If size is 1, it means the normalized form is just a null terminator (empty string).
+    // Return the sanitized input unchanged to preserve the original input.
+    if (size == 1)
+    {
+        return sanitized;
+    }
+
     // Perform the normalization.
     std::wstring normalized;
     normalized.resize(size);
-    NormalizeString(NormalizationC, sanitized.c_str(), -1, &normalized[0], size);
+    int actualSize = NormalizeString(NormalizationC, sanitized.c_str(), -1, &normalized[0], size);
+    
+    // If normalization failed on the second call, return sanitized input.
+    if (actualSize <= 0)
+    {
+        return sanitized;
+    }
 
     // Remove the explicit null terminator added by NormalizeString.
     if (!normalized.empty() && normalized.back() == L'\0')
@@ -50,6 +63,13 @@ static std::wstring SanitizeAndNormalize(const std::wstring& input)
         normalized.pop_back();
     }
 
+    // If normalization resulted in an empty string, return the sanitized input instead.
+    // This can happen with certain edge-case inputs where the normalized form is empty.
+    if (normalized.empty())
+    {
+        return sanitized;
+    }
+
     return normalized;
 }
 

src/modules/powerrename/unittests/CommonRegExTests.h

@@ -695,6 +695,40 @@ TEST_METHOD(VerifyUnicodeAndWhitespaceNormalizationRegex)
     VerifyNormalizationHelper(UseRegularExpressions);
 }
 
+TEST_METHOD(VerifyDollarSignEndOfLineRegex)
+{
+    CComPtr<IPowerRenameRegEx> renameRegEx;
+    Assert::IsTrue(CPowerRenameRegEx::s_CreateInstance(&renameRegEx) == S_OK);
+    DWORD flags = UseRegularExpressions;
+    Assert::IsTrue(renameRegEx->PutFlags(flags) == S_OK);
+
+    // Test that $ matches end of line and allows appending text
+    PWSTR result = nullptr;
+    Assert::IsTrue(renameRegEx->PutSearchTerm(L"$") == S_OK);
+    Assert::IsTrue(renameRegEx->PutReplaceTerm(L" X") == S_OK);
+    unsigned long index = {};
+    Assert::IsTrue(renameRegEx->Replace(L"foobar", &result, index) == S_OK);
+    Assert::AreEqual(L"foobar X", result);
+    CoTaskMemFree(result);
+}
+
+TEST_METHOD(VerifyDollarSignWithTextRegex)
+{
+    CComPtr<IPowerRenameRegEx> renameRegEx;
+    Assert::IsTrue(CPowerRenameRegEx::s_CreateInstance(&renameRegEx) == S_OK);
+    DWORD flags = UseRegularExpressions;
+    Assert::IsTrue(renameRegEx->PutFlags(flags) == S_OK);
+
+    // Test that word$ matches end of specific word
+    PWSTR result = nullptr;
+    Assert::IsTrue(renameRegEx->PutSearchTerm(L"bar$") == S_OK);
+    Assert::IsTrue(renameRegEx->PutReplaceTerm(L"baz") == S_OK);
+    unsigned long index = {};
+    Assert::IsTrue(renameRegEx->Replace(L"foobar", &result, index) == S_OK);
+    Assert::AreEqual(L"foobaz", result);
+    CoTaskMemFree(result);
+}
+
 #ifndef TESTS_PARTIAL
 };
 }