FGenerator 3.0.1

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FGenerator

Building C# Source Generator as a File-based App

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✨ Key Features

• Declarative: Say what to scan or inject and skip Roslyn internals; everything you need is bundled.
• Focus on Logic: The framework finds targets, generates code and report diagnostic on your behalf.
• Single File: Optimized for file-based app project; develop full-featured generator and analyzer in a day.
• Type-Handling: Nested/generic-safe naming and partial declarations stay consistent without boilerplate.
• AI Agent Friendly: Produce valid and well-designed generators without extra prompts and instructions.
• Unity Engine Supported: Unity 2022.3.12 or newer is supported.

⚡ Quick Start

🧩 Minimal Generator Code

A trimmed-down starting point for a generator that targets an attribute named MyGen:

#:sdk FGenerator.Sdk@3.0.1

using FGenerator;
using Microsoft.CodeAnalysis;

// Decorate with Generator attribute from Roslyn (don't need to declare type in namespace)
[Generator]
public sealed class MyGen : FGeneratorBase  // Inherit from FGeneratorBase
{
    // Diagnostic settings
    protected override string DiagnosticCategory => nameof(MyGen);
    protected override string DiagnosticIdPrefix => "MYGEN";  // e.g., MYGEN001
  
    // Targets MyGen and MyGenAttribute (null to targets all types)
    protected override string? TargetAttributeName => "MyGen";

    // Generates target attribute for compilation (attribute should be declared as 'internal sealed')
    protected override string? PostInitializationOutput =>
        @"namespace MyGenNamespace { internal sealed class MyGenAttribute : System.Attribute { } }";

    // Optional: default is false.
    // Set to true when you need target.Compilation is set (always set when TargetAttributeName is null).
    protected override bool CombineCompilationProvider => true;

    // Analyze and generate source code
    protected override CodeGeneration? Generate(Target target, out AnalyzeResult? diagnostic)
    {
        diagnostic = null;

        if (!target.IsPartial)
        {
            // Report error diagnostic for IDE
            diagnostic = new AnalyzeResult(
                "001", "Type must be partial", DiagnosticSeverity.Error,
                $"Type '{type.Name}' must be declared as partial to use MyGen.");

            return null;
        }

        // Generate source code
        var source =
$@"{target.ToNamespaceAndContainingTypeDeclarations()}
    partial {target.ToDeclarationString(modifiers: false)}
    {{
        public string Generated => ""Hello from MyGen!"";
    }}
{target.ToNamespaceAndContainingTypeClosingBraces()}";

        return new CodeGeneration(target.ToHintName(), source);
    }
}

How to reference the specific version of FGenerator:

Use #:package and #:property directives instead of #:sdk.

#:package FGenerator@<<SPECIFY DESIRED VERSION HERE>>
#:property TargetFramework=netstandard2.0
#:property IsRoslynComponent=true
#:property PublishAot=false
#:property LangVersion=latest
#:property OutputType=Library
#:property GenerateDocumentationFile=false
#:property ImplicitUsings=enable

🧭 Working with Target Members, Attributes and Metadata

Here shows the basic flow for dealing with the target members or other metadata including attributes and its constructor parameter. See sample/ folder for more details.

// Compilation to get semantic models or conversions.
// (Need to set `CombineCompilationProvider` to have property available)
var compilation = target.Compilation;

// Iterate over visible members (excluding implicit, nested types, getter and setter methods)
foreach (var member in target.Members)
{
    // To iterate over only fields, instead use target.Members.OfType<IFieldSymbol>()
    // To process getter/setter methods, get them via IPropertySymbol.Get/SetMethod
}

// Type or method generic parameters (empty when not generic)
var typeParams = target.GenericTypeParameters;

// Iterate over nested types (depth-first traversal)
var nestedTypes = target.NestedTypes;

// Containing types (outermost -> innermost)
var containingTypes = target.ContainingTypes;

// The first RawAttributes entry corresponds to TargetAttributeName.
var attr = target.RawAttributes.FirstOrDefault();
if (attr == null)
{
    diagnostic = new AnalyzeResult("004", "Attribute missing", DiagnosticSeverity.Error, "StackArrayGenerator attribute could not be resolved.");
    return null;
}

var length = (attr.ConstructorArguments.Length != 0 && attr.ConstructorArguments[0].Value is int LEN) ? LEN : -1;
if (length <= 0)
{
    diagnostic = new AnalyzeResult("005", "Length must be positive", DiagnosticSeverity.Error, "Specify a positive length in [StackArrayGenerator].");
    return null;
}

🛠️ Helper Methods for Target and ISymbol

Symbol display/declaration strings:

// Declaration string (optionally include modifiers/constraints)
var decl = target.ToDeclarationString(modifiers: true, genericConstraints: true);

// Friendly names with options for namespace/generics/nullability
var fullName = target.ToNameString();                   // global::My.Namespace.MyType.NestedType<T?>
var simpleName = target.ToNameString(localName: true);  // NestedType<T?>
var bareName = target.ToNameString(localName: true, noGeneric: true, noNullable: true);  // NestedType

// Builds an identifier string that is intended to be unique within an assembly
// that can be used to generate non-conflicting field name in large partial classes or etc.
var id = target.ToAssemblyUniqueIdentifier("_");  // My_Namespace_MyType_NestedTypeT1

Partial scaffolding (nested/generic safe):

// No boilerplate required for generating correct partial class/struct/record
// e.g., namespace My.Namespace {
//         partial class ContainingType {
//           partial record struct OtherContainingType {
var open = target.ToNamespaceAndContainingTypeDeclarations();

// Emit members...
var decl = $"partial {target.ToDeclarationString(modifiers: false)} {{ }}";

// Close declarations
var close = target.ToNamespaceAndContainingTypeClosingBraces();

Containing type only (no namespace):

// Useful when mirroring type hierarchy in other namespace
var open = target.ToContainingTypeDeclarations();

// Emitting code...

var close = target.ToContainingTypeClosingBraces();

Visibility keyword helper:

// Accessibility keyword including trailing space, e.g., "public "
var visibility = target.ToVisibilityString();

Deterministic hint names (nested/generic safe):

var hint = target.ToHintName();  // e.g., My.Namespace.Type.MyNestedT1.g.cs

📦 Building and Packaging

Use the CLI to build generator projects (defaults to Release; pass --debug for Debug):

dnx FGenerator.Cli -- build "generators/**/*.cs" --output ./artifacts

Options:

• --unity to emit Unity .meta files alongside DLLs (Unity 2022.3.12 or newer).
• --merge to merge build outputs into a single DLL.
• --force to overwrite existing files.
• --debug to build with -c Debug instead of Release.