Скачать или смотреть How to Qualify Symbols with a CSharpSyntaxRewriter in Roslyn Source Generators

Learn to fully qualify symbols in Roslyn source generators using a custom CSharpSyntaxRewriter for improved code generation.
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A Comprehensive Guide to Qualifying Symbols with a CSharpSyntaxRewriter in Roslyn

When creating source generators in Roslyn, you may encounter specific challenges that need addressing—one common problem is the inability to fully qualify symbols from an Initializer of a VariableDeclaratorSyntax. This complexity often arises from the diverse structures of code you might be working with. For instance, consider a scenario where you define a field with a simple initializer like Foo _fooField = Foo.Baz;. However, your goal is to output a fully qualified version: MyNamespace.SomeStuff.Foo _fooField = MyNamespace.SomeStuff.Foo.Baz;. This guide will guide you through achieving this by creating a CSharpSyntaxRewriter that accurately visits and modifies syntax nodes.

Understanding the Problem

In situations where you need a fully-qualified initializer, the key is to traverse the syntax tree properly and resolve symbols using a SemanticModel. The challenge lies in identifying how to replace each component of a member access expression with its fully qualified version, ensuring you don't end up with incorrect paths such as Foo.MyNamespace.SomeStuff.Foo.Baz.

Sample Code Example

Here’s an example of code you might be working with:

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You want to generate:

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To achieve this, we can use a custom CSharpSyntaxRewriter to traverse and modify the syntax tree appropriately.

Developing a Solution

Step 1: Create a Custom CSharpSyntaxRewriter

We start by defining a class that extends CSharpSyntaxRewriter. This class will implement methods for visiting member access expressions to replace their names with fully qualified versions.

Initializing the QualifiedWriter Class

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Step 2: Visiting Member Access Expressions

Next, we implement the VisitMemberAccessExpression method. This method will use a helper function to resolve the symbols throughout nested member access expressions.

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Step 3: Applying the Rewriter

Now that we have our QualifiedWriter, we can apply it to the initializer expression to get a corrected version.

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Conclusion and Further Considerations

The provided solution effectively qualifies member access expressions, but keep in mind that this implementation may not be foolproof. Scenarios involving more complex expressions, such as constructors or static members accessed in a certain way, might require additional handling.

Feel free to expand upon this code or adapt it for specific needs in your source generator projects. The world of Roslyn is nuanced, and as you explore further, you may uncover more challenges and corresponding solutions.

With these guidelines, you're now equipped to qualify symbols in a Roslyn syntax tree effectively!