ymassad / purityanalyzer Goto Github PK

@ymassad hey Yacoub, I recently read your articles on dotnetcurry and wanted to try your extension in VS2019. I downloaded the .vsix file and was met with this curious error.

In any event, thanks!

Can the analyzer also work with the [Pure] attribute from System.Diagnostics.Contracts?

I don't want to introduce an extra [IsPure] attribute. There is one already in the framework. I would prefer to use that one. A lot of OSS projects have annotated there code with the [Pure] attribute. I want to use this analyzer to check their implementation.

Thanks,

Fons

For example,

int number = 1;
string str = $"{number}";

Is impure because Int32.ToString() is impure.

I think that PurityAnalyer should not allow this:

public static void M()
{
    FormattableString fs = $"{1}";

    Do(fs);
}
public static void Do(FormattableString fs)
{
    var result = FormattableString.Invariant(fs);
}

As far as Do is concerned, the arguments in fs might have impure ToString methods, and we cannot know that at compile time.

So we cannot consider FormattableString.Invariant to be pure. What we can do however, is give special handling to this:

FormattableString.Invariant( $"{1}");

That is, when the parameter given to Invariant is a constant.

By default, as far as PurityAnalyzer is concerned, a method is either pure or not.

However, this might be used often enough to justify special handling.

Hi @ymassad,

I am setting this issue as a placeholder for Visual Studio 2022 support.

Thank you in advance for your extension and work! 🥇

The PurityAnalyzer is now only a Visual Studio Extension. Can you also publish a NuGet package for it? I want to use it without the need to install the extension. The NuGet (analyzer) package would allow me to analyze only certain projects in my solution.

Regards,

Fons

While working on #5 I've tested latest (github) version of PurityAnalyzer and found strange behavior related to casting.

Given following code:

 [IsPure] private static string AliasWithNo(int number) => "test_" + number;

PurityAnalyzer underlined number and said:

Cast is impure.
Error casting.
From: System.Int32
To: System.Object
Relevant methods: System.Object.ToString()

This make me notice that int.ToString() is impure but I don't understand why cast to object is impure?
Strangely enough changing "test_" + number to $"test_{number}" removes the error.

But, knowing that int.ToString() is impure I've changed it to FormattableString.Invariant($"test_{number}") and added

System.FormattableString, Invariant(System.FormattableString)
System.FormattableString, ToString()

to PureMethods.txt
but then I've again received error

Cast is impure.
Error casting.
From: System.String
To: System.FormattableString
Relevant methods:
System.FormattableString.get_Format
System.FormattableString.GetArguments
System.FormattableString.get_ArgumentCount
System.FormattableString.ToString
System.FormattableString.ToString
System.Object.GetHashCode

• Why is casting to object impure? (I guess because of impure ToString())
• How to resolve cases like above?
• is GetHashCode really impure?
• Or maybe it's just unfinished feature