fix: prevent IndexOutOfRangeException in MethodDataSource analyzer

[thomhurst]

Summary

• Fix IndexOutOfRangeException crash in TestDataAnalyzer.CheckMethodDataSource() when attribute constructor arguments are missing or cannot be resolved
• Add defensive checks to handle malformed attributes gracefully

Root Cause

The analyzer was accessing ConstructorArguments[0] and ConstructorArguments[1] without checking if the array had elements. This caused crashes when:

• The attribute's constructor arguments couldn't be resolved during compilation
• There were other compilation errors in the user's code
• The attribute was malformed

The exception was being caught by the analyzer framework and converted into a cryptic TUnit0001 error message.

Test plan

• Verify the analyzer no longer crashes with missing constructor arguments
• Run existing analyzer tests to ensure no regression

Fixes #4540

🤖 Generated with Claude Code

[thomhurst]

Summary

Fixes crash in analyzer when MethodDataSource attribute has malformed or unresolved constructor arguments during compilation.

Critical Issues

None found ✅

Suggestions

Consider adding a length check for ConstructorArguments[0] access (line 415)

While the PR fixes the IndexOutOfRangeException for ConstructorArguments[1], it still accesses ConstructorArguments[0] without verifying the array has at least one element (line 415 in the diff context):

var type = attribute.AttributeClass?.IsGenericType == true
    ? attribute.AttributeClass.TypeArguments.First()
    : attribute.ConstructorArguments[0].Value as INamedTypeSymbol ?? testClassType;

The guard check on line 413-416 (after the fix) returns early if the array is empty, which protects line 415. However, for defensive coding and clarity, you might want to reorder the logic to check the array before any access, or add an explicit length check before line 415.

Example:

if (attribute.ConstructorArguments.IsDefaultOrEmpty || attribute.ConstructorArguments.Length == 0)
{
    return;
}

var type = attribute.AttributeClass?.IsGenericType == true
    ? attribute.AttributeClass.TypeArguments.First()
    : (attribute.ConstructorArguments.Length > 0 ? attribute.ConstructorArguments[0].Value as INamedTypeSymbol : null) ?? testClassType;

This is a minor suggestion - the current fix does protect against the crash through the early return.

Verdict

✅ APPROVE - No critical issues

The fix appropriately addresses the reported bug by adding defensive checks for missing constructor arguments. The analyzer will now gracefully skip validation when attributes are malformed due to compilation errors, allowing the compiler to report the actual error instead of causing an analyzer crash.