Diagnostics

Diagnostics

ResourceKit reports diagnostics with SGxxxx IDs to help you fix model issues quickly. The rules are evaluated by the bundled ResourceKitDiagnosticAnalyzer (and the source generator uses the same shared rule set to decide what can be generated).

ResourceKit also ships ResourceKitDiagnosticSuppressor, which automatically suppresses CS8618 for non-nullable IResourceBuilder<T> properties declared on resource kits — these are populated at runtime during the BuildResource/ConfigureResource lifecycle, so the “must contain a non-null value when exiting the constructor” warning does not apply.

Diagnostic reference

ID	Severity	What it means
SG0001	Error	A participating class must be partial
SG0002	Info	Host kit exists but no resources were defined
SG0003	Warning	Resources exist but no host kit was defined
SG0004	Error	More than one [HostKit] class was found
SG0005	Error	Two resources map to the same generated property name
SG0006	Error	A resource does not derive from the expected generated base
SG0007	Error	Resource name could not be inferred and Name was not set
SG0008	Error	Explicit PropertyName is not a valid C# identifier
SG0009	Error	Missing IServiceCollection dependency
SG0010	Error	Missing configuration binder dependency
SG0011	Error	Missing options configuration extensions dependency
SG0012	Error	Non-empty constructors are not supported on attributed classes
SG0013	Error	Mixed ResourceDefinition and ResourceDefinition<TResource> usage on one class
SG0014	Error	Non-generic ResourceDefinition requires explicit compatible base type
SG0015	Error	Generic ResourceDefinition<TResource> cannot declare explicit base type
SG0016	Error	No Aspire resource type could be inferred/found
SG0017	Warning	An IResourceBuilder<T> property is never assigned in BuildResource or ConfigureResource
SG0018	Warning	A project resource kit does not add the declared project via AddProject<T>()
SG0019	Warning	A project resource kit declares an explicit base class that does not use ProjectResource
SG0020	Error	An OptionsHelper.Assign action sets more than one property path

See Attributes Reference for the rules tied to attribute styles, and Project Resources for SG0018/SG0019 specifics.

Execution-only vs generation-blocking rules

SG0017, SG0018, and SG0019 are execution-only rules. They report problems that break the resource at runtime (an unset builder property, a project that is never registered, or a base class that cannot build a project) but they do not prevent source generation. They are reported as warnings so generation always proceeds — for example, a resource kit whose BuildResource does not yet register its declared project via AddProject<T>() is still generated (and the host kit is still emitted) so the user can complete the override instead of losing the whole output. Only Error-severity rules (SG0001–SG0016) block generation.

OptionsHelper.Assign action with multiple property paths (SG0020)

Each OptionsHelper.Assign<TOptions>(...) action must set exactly one property path. A block-bodied lambda such as the following is rejected at compile time:

OptionsHelper.Assign<ShopHostKitOptions>(o =>
{
    o.API.IsEnabled = false;
    o.API.Name = "api-test";
});

Split each property into its own assignment argument instead:

OptionsHelper.Assign<ShopHostKitOptions>(
    o => o.API.IsEnabled = false,
    o => o.API.Name = "api-test"
);

Visual Studio offers a “Split into separate assignments” code fix that performs this conversion for you. See OptionsHelper and Source Generator Behaviors.

Fast troubleshooting checklist

1. Ensure host/resource classes are marked partial.
2. Ensure exactly one [HostKit] class exists in the compilation.
3. Ensure resource property names are unique (explicit PropertyName can help).
4. Ensure each resource uses a compatible base and definition attribute style.
5. Set explicit Name when inference cannot determine resource name.

Common fixes

Duplicate generated property names (SG0005)

Use unique PropertyName values:

[ResourceDefinition<ProjectResource>("api", PropertyName = "Api")]
[ResourceDefinition<ProjectResource>("admin", PropertyName = "AdminApi")]

Invalid PropertyName (SG0008)

Use valid C# identifiers only (Api, RedisCache, OrderDb, etc.).

Multiple host kits (SG0004)

Keep one [HostKit] per compilation; split scenarios into separate projects if needed.

Mixed attribute styles (SG0013)

Use exactly one style per class:

• [ResourceDefinition("name")]
• or [ResourceDefinition<TResource>("name")]

Do not apply both to the same class.

Base-type mismatch by style (SG0014 / SG0015)

• If you use non-generic [ResourceDefinition("name")], declare an explicit compatible base.
• If you use generic [ResourceDefinition<TResource>("name")], do not declare an explicit base.

Unassigned IResourceBuilder<T> property (SG0017)

Every IResourceBuilder<T> property on a resource kit (nullable or not) must be assigned in either BuildResource or ConfigureResource. CS8618 is automatically suppressed for these properties because they are populated at runtime, so SG0017 is the signal that a property is never set:

[ResourceDefinition<AzureSqlServerResource>("sql")]
sealed partial class SqlServerKit
{
  public IResourceBuilder<AzureSqlDatabaseResource> Database { get; private set; }

  protected override void ConfigureResource()
  {
    Database = ResourceBuilder.AddDatabase("changeops-db", "ChangeOps");
    base.ConfigureResource();
  }
}