dbolin/apex.analyzers

Roslyn powered analyzers for C# to support convention defined architecture

Apex.Analyzers

Roslyn powered analyzers for C# to support convention defined architecture

Immutable Types

Nuget Package

Provides an ImmutableAttribute type which can be applied to classes, structs, and interfaces. The analyzer ensures that the following rules hold for types marked with the attribute.

ID	Severity	Rule	Code Fix
IMM001	Error	Fields in an immutable type must be readonly	Yes
IMM002	Error	Auto properties in an immutable type must not define a set method	Yes
IMM003	Error	Types of fields in an immutable type must be immutable	No
IMM004	Error	Types of auto properties in an immutable type must be immutable	No
IMM005	Warning	'This' should not be passed out of the constructor of an immutable type	No
IMM006	Error	The base type of an immutable type must be 'object' or immutable	No
IMM007	Error	Types derived from an immutable type must be immutable	No
IMM008	Warning	'This' should not be passed out of an init only property method of an immutable type	No

Whitelisting types via additional files

The immutable types analyzer allows specifying types to be whitelisted in an Additional File.

The name of the additional file is "ImmutableTypes.txt" and the format of the file is one namespace qualified type name per line. For example:

System.Xml.Linq.XName
System.Func`1

apex.analyzers's Issues

Version 1.1 does not work with Visual Studio 16.4

The new Microsoft.CodeAnalysis package that's referenced in 1.1 (Microsoft.CodeAnalysis 3.5) isn't included in Visual Studio 2019 Update 4, so compiling with that version of MSBuild produces this warning --

CSC : warning CS8032: An instance of analyzer Apex.Analyzers.Immutable.ApexAnalyzersImmutableAnalyzer cannot be created from C:\Users\markwelsh\source\repos\ApexExample\packages\Apex.Analyzers.Immutable.1.1.0\analyzers\dotnet\cs\Apex.Analyzers.Immutable.dll : Could not load file or assembly 'Microsoft.CodeAnalysis, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified..

Is there a way to work around this? Or would it be possible to roll back to the version supported by 16.4? That's the most recent servicing baseline.

Referencing the analyzer package with PrivateAssets="All"

Currently you have to reference the analyzer with PrivateAssets="All" to prevent the analyzer from flowing to referencing projects. However, this means referencing projects don't reference the Attributes package, which can cause issues with runtime reflection.

PrivateAssets="analyzers" would be the preferred solution but needs NuGet/Home#6279 to be resolved.

One workaround is to reference the Attributes package directly in projects that need it.

Could you add a strong name?

Hi, thanks for this handy tool!

Could you add strong name to both Apex.Analyzers.Immutable and Apex.Analyzers.Immutable.Attributes?
My project is strong named so I get CS8002 error when I try to use your assemblies.

error CS8002: Referenced assembly 'Apex.Analyzers.Immutable.Attributes, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not have a strong name.

Helpers could be exposed publicly (or via separate NuGet package)

We're using your immutability analyzers to detect mutability problems in our code. We have our own set of analyzers that build on top of yours. Specifically, we are trying to prevent static state that is mutable. Our analyzers use similar logic to what is defined in your Helpers class. Could this be made public or exposed as a separate Apex.Analyzers.Helpers package?

Whitelist is hard-coded

Could the list of whitelisted types be configurable? Similar to Microsoft's BannedApiAnalyzer, there could be an additional file added to the analyzed project that could extend the list of white-listed types. Happy to implement this. Just don't want to go down this road unless it's likely to be accepted.

OnFaith is not included in latest nuget package (0.9.3)

I saw in the source that you've implemented the OnFaith parameter but it seems that the latest published nuget package does not contain it: https://www.nuget.org/packages/Apex.Analyzers.Immutable.Attributes/0.9.3
Or am I missing something?

C# 9 Init-only property setters trigger IMM002

The following auto-property will trigger IMM002, even though the property is immutable after the object is initialized:

public int Property { get; init; }

I can look at creating a Pull Request to address this if you'd like.

Delegates with mutable parameters are treated as mutable

We now have a way to mark arbitrary types immutable via configuration. This allows us to configure System.Action`1, for example, as immutable without impacting other consumers of the analyzers. However, we're still experiencing a fair amount of pain due to the generic type argument checking.

For example this is a violation:

[Immutable]
class Test
{
    public Action<NotImmutable> Action { get; }
}

Even though Action`1 is treated as immutable, its generic type argument (NotImmutable) is not, and so it produces an IMM004.

I know that delegates are treated as mutable as a conscious design choice, but might this be reconsidered? Another corner case (like state-capturing lambdas) that is not covered would be:

[Immutable]
class Test
{
    private readonly object _random;

    public Test(object random)
    {
        _random = random;
    }
    public int Value => ((System.Random)_random).Next(0, 10);
}

I'm not arguing that this should be caught -- simply that there will always be ways to subvert the rules if someone is truly determined to do so.

Alternately, could we add configuration to control the treatment of delegates? The Microsoft analyzers now support options defined in an .editorconfig. Unfortunately their implementation is internal, so cannot be called directly. But the code is open-source and could be incorporated.