CA2241 should respect new StringSyntaxAttribute.CompositeFormat

[stephentoub]

Analyzer

Diagnostic ID: CA2241

Describe the improvement

"CA2241: Provide correct arguments to formatting methods" has a hardcoded list of methods that accept a composite format string. But in .NET 7, the new StringSyntaxAttribute exists and includes a StringSyntaxAttribute.CompositeFormat, which has been used to annotate many string parameters that are expected to be passed a composite format string. CA2241 should ideally apply to any parameter that accepts such a format string, at least in terms of validating the correctness of the syntax of the string.

Describe suggestions on how to achieve the rule

For any method invocation, look at the parameters to see if any is attributed with [StringSyntax(StringSyntaxAttribute.CompositeFormat)], and if it is, validate that the argument being passed for that parameter is correctly formed (as it does today for the hardcoded list).

[Evangelink]

@stephentoub I have a couple of questions:

• Is it possible to have more than 1 parameter with this attribute on a method call?
• If defined on an interface/abstract, is user forced to redefined it or is it "inherited"?

[stephentoub]

Is it possible to have more than 1 parameter with this attribute on a method call?

Yes, though that would be extremely rare. We have hundreds of parameters attributed now in .NET 7 and I don't believe we have any such cases.

is user forced to redefined it or is it "inherited"?

From a reflection standpoint, it's not inherited.

[manfred-brands]

@stephentoub Can I put my hand up for this one?

[stephentoub]

Go for it. Thanks!