[dotnet] Fix RelativeBy.Near and empty list return, port Java tests

[RenderMichael]

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Description

Bug 1:
The Near method is now fixed, with a "blind" copy of what the Java code is doing.

Bug 2:
When querying for elements using the relative locator, sometimes you are returned nothing. In that case, the response JSON is [], and the de-serializer doesn't know you're getting back web elements.

As such, the response object has a runtime type of ReadOnlyCollection<object> and the cast as ReadOnlyCollection<IWebElement> fails (ie, returns null).

I can't think of a more elegant solution that doesn't require gutting the JavaScript execution process.

One more reason the as operator is not the right tool when the type is expected to be an exact match 🫠

Motivation and Context

Fixes #13610

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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PR Type

Bug fix, Tests

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Description

• Fixed the issue where relative locators returned null instead of an empty collection when no matches are found.
• Added logic to handle the deserialization quirk by returning an empty collection.
• Introduced a new test to verify that an empty list is returned when no elements are found using relative locators.

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Changes walkthrough 📝

	Relevant files
Bug fix	RelativeBy.cs Handle empty results in relative locators                                dotnet/src/webdriver/RelativeBy.cs Added handling for empty results when using relative locators. Implemented conditional logic to return an empty collection when no elements are found. Included debug assertion for unreachable code paths. +27/-2
Tests	RelativeLocatorTest.cs Add test for empty result in relative locators                      dotnet/test/common/RelativeLocatorTest.cs Added a test to verify behavior when no elements are found using relative locators. Ensured the test checks for an empty list return. +11/-0

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[qodo-merge-pro]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 PR contains tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Code Smell The unreachable code block with Debug.Fail() should be reviewed. If this code path is truly unreachable, consider removing it entirely rather than keeping dead code. Type Safety The final fallback cast to ReadOnlyCollection could throw an InvalidCastException. Consider adding explicit type checking or error handling.

[qodo-merge-pro]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Best practice	✅ Replace debug assertion with exception throw to properly handle unexpected states in production code Suggestion Impact: The Debug.Fail call was replaced with an exception throw, aligning with the suggestion to handle unexpected states properly. However, the exception type and message differ from the suggestion. code diff: - Debug.Fail("Unreachable"); - return elementsObj.Select(element => (IWebElement)element).ToList().AsReadOnly(); - } - - return (ReadOnlyCollection<IWebElement>)rawElements; + } + + throw new WebDriverException($"Could not de-serialize element list response{Environment.NewLine}{rawElements}"); The Debug.Fail call with "Unreachable" suggests this code path should never be hit, but the code after it is still executed. Consider throwing an InvalidOperationException instead to fail fast if this "impossible" state is reached. dotnet/src/webdriver/RelativeBy.cs [133-134] -Debug.Fail("Unreachable"); -return elementsObj.Select(element => (IWebElement)element).ToList().AsReadOnly(); +throw new InvalidOperationException("Unexpected state: ReadOnlyCollection<object> with non-zero elements"); Apply this suggestion Suggestion importance[1-10]: 8 Why: This is a significant improvement for production code reliability. Replacing Debug.Fail with an exception throw ensures proper error handling in all environments and prevents silent failures in production.	8
Enhancement	Simplify type checking and casting logic using pattern matching for better code readability and maintainability Consider using pattern matching with 'is' to simplify the type checking and casting logic. This would make the code more concise and eliminate the need for an explicit cast at the end. dotnet/src/webdriver/RelativeBy.cs [114-137] -if (rawElements is ReadOnlyCollection<IWebElement> elements) +return rawElements switch { - return elements; -} + ReadOnlyCollection<IWebElement> elements => elements, + ReadOnlyCollection<object> { Count: 0 } => + #if NET8_0_OR_GREATER + ReadOnlyCollection<IWebElement>.Empty, + #else + new List<IWebElement>().AsReadOnly(), + #endif + _ => (ReadOnlyCollection<IWebElement>)rawElements +}; -if (rawElements is ReadOnlyCollection<object> elementsObj) -{ - if (elementsObj.Count == 0) - { - #if NET8_0_OR_GREATER - return ReadOnlyCollection<IWebElement>.Empty; - #else - return new List<IWebElement>().AsReadOnly(); - #endif - } - - Debug.Fail("Unreachable"); - return elementsObj.Select(element => (IWebElement)element).ToList().AsReadOnly(); -} - -return (ReadOnlyCollection<IWebElement>)rawElements; - Apply this suggestion Suggestion importance[1-10]: 6 Why: The suggestion offers a more modern and concise approach using pattern matching, which improves code readability while maintaining the same functionality. However, it's primarily a stylistic improvement rather than a critical fix.	6

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[RenderMichael]

Tests are a one-to-one clone of the java tests: https://github.com/SeleniumHQ/selenium/blob/trunk/java/test/org/openqa/selenium/support/locators/RelativeLocatorTest.java

With the exception of the one C#-deserializer-specific test at the bottom