LAMA0900: Non-experimental code uses an experimental API

Cause

The ExperimentalAttribute aspect marks a declaration, typically a type or a member, as experimental. Metalama then validates every reference to this declaration and to its members, and reports LAMA0900 for each reference from code that isn't experimental.

A reference is allowed, and doesn't produce the warning, in the following situations:

• The referencing code is contained in the experimental declaration itself.
• The referencing declaration, or one of its containing declarations, is also marked with [Experimental].

In the message, <ReferencedDeclaration> is the experimental declaration and <ReferencedDeclarationKind> its kind, for instance type or method. If you pass a description to the [Experimental] attribute, the message ends with this description.

In the following example, the PdfExporter class is experimental, and the ReportService.Save method, which isn't experimental, calls it.

1using Metalama.Extensions.Architecture.Aspects;
2
3namespace Doc.LAMA0900.Error;
4
5[Experimental]
6public static class PdfExporter
7{
8    public static void Export( string path ) { }
9}
10
11public class ReportService
12{
13    public void Save()
14    {
15        // Warning: PdfExporter is experimental, but Save is not.
        Warning LAMA0900: The 'PdfExporter' type is experimental.

16        PdfExporter.Export( "report.pdf" );
17    }
18}
19

Resolution

Depending on your intent, do one of the following:

• Mark the referencing declaration, or its containing type, with [Experimental] as well, so that the experimental status propagates to the code that depends on the API. The following example does this. Note that [Experimental] can only be applied to declarations that are public or protected.
• Stop using the experimental API until it's stable.
• If you own the API and it's now stable, remove the [Experimental] attribute.

1using Metalama.Extensions.Architecture.Aspects;
2
3namespace Doc.LAMA0900.Fixed;
4
5[Experimental]
6public static class PdfExporter
7{
8    public static void Export( string path ) { }
9}
10
11public class ReportService
12{
13    // Fixed: the method that uses the experimental API is marked as experimental too.
14    [Experimental]
15    public void Save()
16    {
17        PdfExporter.Export( "report.pdf" );
18    }
19}
20

See also

• Marking experimental APIs
• Verifying architecture