Add null checks for node and its parent in NewLineUserSettingFormattingRule.IsControlBlock

[tcNickolas]

Customer scenario

If syntax tree has NamespaceDeclaration as a root node instead of CompilationUnit, IsControlBlock is called for NamespaceDeclaration node which has null Parent, and this code throws NullReferenceException at line 19. This is not a common scenario, as valid trees are supposed to have CompilationUnit as a root node, but it's better to have the checks in place.

Workarounds, if any

Use CompilationUnit as root node of the tree.

Risk

Low because these checks were present in the code before.

Performance impact

Low perf impact because the only extra work done is two null checks.

Is this a regression from a previous update?

Yes, these checks were removed in 146b391.

How was the bug found?

Customer reported

[heejaechang]

can we add a test as well?

[tcNickolas]

Sure, I can try and figure out how to write a test for this. Do you know whether there is a test for a similar scenario in the codebase which I could use as an example? All existing tests seem to construct a syntax tree which has CompilationUnit as a root

[jaredpar]

We apologize, but we are closing this PR due to code drift. We regret letting this PR go so long without attention, but at this point the code base has changed too much for us to revisit older PRs. Going forward, we will manage PRs better under an SLA currently under draft in issue #26266 – we encourage you to add comments to that draft as you see fit. Although that SLA is still in draft form, we nevertheless want to move forward with the identification of older PRs to give contributors as much early notice as possible to review and update them.

If you are interested in pursuing this PR, please reset it against the head of master and we will reopen it. Thank you!