safern / applynullabledecorators Goto Github PK

Currently, if a method throws when doing:

if (x is null) throw new ArgumentNullException(nameof(x));

the tool doesn't catch that, that argument is not nullable.

Add test coverage with various different scenarios that the tool should support:

1. Method chaining (calling overrides or internal methods that do argument validation)
2. Internal/Private methods using Debug.Assert
3. "is null" pattern.
4. operators -> operator !=(string a, string b)
5. Internal/Private methods, deeper analysis, if it dereference an argument without null validation, should assume it can't be null as well.
   ....
   etc.

Visit constructor invocations using :this syntax.

Just like we do now for overrides or invocations to other public APIs, for constructors we also have argument validation, so we could hit a scenario like:

public foo(string x) : this(x, 0) { }
public foo(string x, int y) 
{
        if (x == null) throw new ArgumentNullException(nameof(x));
} 

So the tool should understand that x can't be null on either foo constructors.

Right now the tool won't decorate an array or collection with ? for the underlying items, as it doesn't have a way yet to know if an item can be null for an array parameter.

It should do deeper analysis to figure out if an item within the array/collection can be null -> i.e string?[] IEnumerable<object?>

When running the tool on String it didn't annotate the != and == operators at all when it should've marked its arguments as nullable.

We have some places where we do:

_x = x ?? throw new ArgumentNullException(nameof(x));

Therefore x can't be null, the tool, now, would mark it as nullable.

Haven't dug into this area yet, but, the tool doesn't do any generic parameters yet.