Blokyk.CA2254CodeFix

The CA2254 diagnostic (Template should be a static expression) helps you detect logger messages that could be problematic for structured logging, by flagging non-constant message templates, i.e. messages that contain expressions themselves.

Most notably, this includes interpolated strings ($"hello {user.name}!"), which can be pretty annoying to "un-interpolate." This small roslyn codefix aims to address that! Here's an example:

// Before codefix, marked with CA2254
logger.LogDebug($"User {user.Username} uploaded {documents.Count} documents!");

// After codefix
logger.LogDebug("User {Username} uploaded {Count} documents!", user.Username, documents.Count);

Installation

This codefix can be installed just like any package using the dotnet CLI:

dotnet add package Blokyk.CA2254CodeFix

You can also reference it in your project:

<PackageReference Include="Blokyk.CA2254CodeFix" Version="*" />

Details about the expression names

The expressions in the interpolated string need to be replaced with something, so obviously this codefix is quite opinionated. Here are some examples of transformations used to derive the names:

expression	resulting name
foo.bar	Bar
foo.bar()	Bar
foo.bar(alice, bob)	BarOfALiceAndBob
foo is not null	FooIsNotNull
DateTime.UtcNow	DateTime

The actual derivation is mostly done in ExpressionNamer.cs, with a little bit more in CSharpLoggerMessageFixer.cs right now.

If you'd like to suggest a tweak or a new naming rule, don't hesitate to open a new issue or PR, I'm completely open to ideas on this!