[Analyzer] Make types declared in an executable internal

[stephentoub]

Various analyzers only pay attention to internal/private types and members, as changes to public API is visible. For example, analyzers/fixers that find and remove dead code, or that recommend types without derivations be sealed. Applications, rather than libraries, however, typically aren't referenced, and public types/members are likely mistakes, such that if the mistakes are corrected and the types/members have their visibility changed to internal/private, then other analyzers can start making recommendations for them.

The proposal is to add an analyzer/fixer that runs when a compilation's OutputKind is ConsoleApplication or WindowsApplication and that flags all public types, recommending they instead be made internal.

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Issue Details

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Various analyzers only pay attention to internal/private types and members, as changes to public API is visible. For example, analyzers/fixers that find and remove dead code, or that recommend types without derivations be sealed. Applications, rather than libraries, however, typically aren't referenced, and public types/members are likely mistakes, such that if the mistakes are corrected and the types/members have their visibility changed to internal/private, then other analyzers can start making recommendations for them.

The proposal is to add an analyzer/fixer that runs when a compilation's OutputKind is ConsoleApplication or WindowsApplication and that flags all public types, recommending they instead be made internal.

Author:	stephentoub
Assignees:	-
Labels:	area-Meta, code-analyzer, code-fixer
Milestone:	-

[bartonjs]

Video

Looks good as proposed.

Given concerns with some of the templates (e.g. WinForms creating the skeleton for a new form type being default) we're recommending this analyzer be opt-in. But we're probably easily convinced that it should be something else.

Category: Maintainability (?)
Visibility: None (off by default; might be nice if trimmer-style scenarios can flip it on by default)

[marek-safar]

The proposal is to add an analyzer/fixer that runs when a compilation's OutputKind is ConsoleApplication or WindowsApplication and that flags all public types, recommending they instead be made internal.

Could the analyzer run when the output binary contains runnable entry-point?

[CollinAlpert]

Should this consider the OutputKind WindowsRuntimeApplication as well?

[KennethHoff]

I see a lot of the newly added analyzers are opt-in.

How do I as a developer enable them, and more importantly, find which ones to enable? Basically, is there an easily digestible list somewhere?

I remember seeing a few good ones being added, so I worry that I'll forget about them and not benefit from them!

[CollinAlpert]

You can add an .editorconfig file to your solution and then select the severity of the rules you would like. For example:
dotnet_diagnostic.CA1018.severity = warning

More information here

[cremor]

I assume it will also be enabled by setting <AnalysisLevel>latest-all</AnalysisLevel>?

[mavasani]

I assume it will also be enabled by setting <AnalysisLevel>latest-all</AnalysisLevel>?

Indeed, that is correct.