domaindrivendev/Swashbuckle.AspNetCore

Please annotate SchemaRepository.TryLookupByType

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#3,659 opened on Nov 15, 2025

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 (3 comments) (2 reactions) (0 assignees)C# (1,341 forks)batch import
good first issuehelp-wanted

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Description

I was reviewing some code and noticed a hidden bug: null could be returned, but there was no compiler warning. This is because TryLookupByType lacks the [NotNullWhen(true)] annotation, which is used, for example, in IPAddress.TryParse.

It would be helpful if SchemaRepository.TryLookupByType were annotated for nullability, similar to my workaround below:

#nullable enable
public static bool TryLookupByTypeSafe(this SchemaRepository schemaRepository,
    Type type, [NotNullWhen(true)] out OpenApiSchemaReference? referenceSchema)
{
    bool result = schemaRepository.TryLookupByType(type,
        out OpenApiSchemaReference? obliviousReferenceSchema);
    referenceSchema = result ? obliviousReferenceSchema : null;
    return result;
}
#nullable restore

And then the hidden bug becomes a compiler warning:

Contributor guide

Research direction
Add the [NotNullWhen(true)] attribute to the TryLookupByType method's output parameter.
Tech stack
csharp
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
1
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C#Nullable Reference Types
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
85