C#: Fewer alerts in cs/useless-if-statement.

[michaelnebel]

It is not an un-common pattern to write something like

if (b) {
  // Insert some relevant debugging statements here
  // My commented out code.
}

Due to the above our query might seem a bit to noisy. In this PR we remove the alerts, if the empty if-block contains a comment.
We still catch the following examples (where the first one is the most important as it is most likely unintentional).

if (b);

if (b)
{
}

[michaelnebel]

DCA looks good.

[Copilot]

PR Overview

This PR adjusts the behavior of the cs/useless-if-statement query to reduce alerts when an empty if-statement contains a comment. It updates test cases to reflect the new behavior and updates the documentation to clarify that if a comment is present, the statement is not flagged.

Reviewed Changes

File	Description
csharp/ql/test/query-tests/Useless Code/FutileConditional/FutileConditional.cs	Adds test cases that demonstrate when alerts should and should not be raised
csharp/ql/src/change-notes/2025-03-05-useless-if-statement.md	Updates the change notes to document the new behavior for commented if-blocks

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[tamasvajk]

Unrelated to your change, I find it odd to consider this okay.

[michaelnebel]

Yes, I agree. Maybe an idea for a quality query:
Create a new quality query which states that the condition should be inverted (we can also provide good QHelp for that - and I suspect an LLM will be good at figuring out how the fix should look like).

[michaelnebel]

Hmm there is already a button for that in VSCode, so it might not be relevant (but you will have to actively click that).