Fix XML Equality Check by Comparing Parsed XML Structure Instead of Raw Strings #3166
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Pull Request Overview
This PR improves XML equality comparisons by introducing a type-aware, structure-based check for XML documents, fixing false negatives caused by formatting differences. Key changes include:
- Adding a new AreXmlsEqual method for comparing XDocument objects.
- Incorporating the new XML comparison function into the equality dictionary.
- Updating tests to use XDocument-based comparisons instead of raw string comparisons.
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| test/Microsoft.IdentityModel.TestUtils/IdentityComparer.cs | Introduces XML comparison functions and updates equality logic to support XDocument. |
| test/Microsoft.IdentityModel.Xml.Tests/DSigSerializerTests.cs | Modifies tests to compare XML by parsing into XDocument. |
Comments suppressed due to low confidence (2)
test/Microsoft.IdentityModel.TestUtils/IdentityComparer.cs:1189
- The AreXmlsEqual method adds a diff message when xml1 is null but does not return false, which can lead to a NullReferenceException when xml1.Root is accessed later. Consider returning false immediately after detecting a null xml1 and include a properly formatted error message.
if (xml1 == null) localContext.Diffs.Add($"({name1} == null, {name2} == {xml2.ToString()}." );
test/Microsoft.IdentityModel.TestUtils/IdentityComparer.cs:1192
- Similar to the null check for xml1, if xml2 is null the method only adds a diff message without returning false, which may cause a NullReferenceException when xml2.Root is accessed. Consider returning false immediately and correcting the error message formatting.
if (xml2 == null) localContext.Diffs.Add($"({name1} == {xml1.ToString()}, {name2} == null." );
| /// <param name="elem2">The second XML element to compare.</param> | ||
| /// <param name="localContext"></param> | ||
| /// <returns>True if the elements are considered equal, otherwise false.</returns> | ||
| private static bool CompareXmlElements(XElement elem1, XElement elem2, CompareContext localContext) |
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Consider utilizing localContext to add information about the differences found which could help with debugging.
| // Compare the original XML with the re-serialized XML. | ||
| // Parsing the XML strings into XDocument ensures that the comparison is based on | ||
| // structural and content equality rather than raw string differences (formatting, whitespace,...). | ||
| IdentityComparer.AreEqual(XDocument.Parse(theoryData.Xml), XDocument.Parse(xml), context); |
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Consider adding tests for different xml structures and null values to verify IdentityComparer behaves as expected when comparing XML.
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Hi Sruke, thank you for the review. Since these tests focus on IdentityComparer, would it be better to add them to a new test file for better organization, or should I extend the existing test file? Let me know your preference.
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Agree that creating a new file is better for organization.
Fix XML Equality Check by Comparing Parsed XML Structure Instead of Raw Strings
Summary of the changes
Ensures XML comparisons are based on structure instead of raw string equality.
Description
Previously, the test compared XML as raw strings, which caused false negatives due to formatting differences, whitespace, and attribute order. While the expected result was different, the discrepancies were due to formatting rather than actual content differences. This fix ensures XML elements are compared meaningfully, preventing incorrect failures.
Fixes & Improvements:
AreXmlsEqualto handle XML documents as objects rather than raw strings.Fixes #3159