Source Generators

How AutoSDK uses Roslyn incremental source generators for compile-time code generation.

AutoSDK uses Roslyn incremental source generators to generate SDK code at compile time — no runtime reflection, no external build tools.

How It Works

When you add the AutoSDK NuGet package to your project:

MSBuild passes your OpenAPI spec as an AdditionalFile to the compiler
The SdkGenerator (an IIncrementalGenerator) reads the spec
It runs the generation pipeline and emits C# source code
The compiler includes the generated code in your compilation

<!-- Your .csproj -->
<ItemGroup>
  <PackageReference Include="AutoSDK" Version="*-*" PrivateAssets="all" />
  <AdditionalFiles Include="openapi.yaml" />
</ItemGroup>

Incremental Generation

AutoSDK's generator is incremental — it only regenerates when the input spec changes. This makes builds fast even for large specs:

The generator caches the parsed spec and type graph
Only schema changes trigger regeneration
IDE (VS, Rider) gets IntelliSense for generated types in real-time

Generator Architecture

AutoSDK includes two generators:

Generator	Purpose
`SdkGenerator`	Main generator — produces client, models, serialization
`CliGenerator`	Optional — generates a CLI wrapper for the SDK (when `AutoSDK_GenerateCli=true`)

Both are implemented as IIncrementalGenerator for optimal performance.

Source Generator vs CLI

The source generator approach has trade-offs compared to the CLI:

Source Generator Advantages

Zero build step — Just add a NuGet package
IDE integration — IntelliSense, go-to-definition, refactoring
Always in sync — Regenerates on every build when spec changes

CLI Advantages

Simpler trimming — No two-project pattern needed
Inspectable output — Generated files are on disk, easy to review
CI flexibility — Run in any environment with the CLI installed
Spec patching — generate.sh can preprocess specs with jq/yq

Recommendation

Use the CLI for most production SDKs. It's simpler, more flexible, and produces inspectable output. The source generator is best for rapid prototyping or when you want zero configuration.