Setting the OpenAPI spec version not working

[Zylvian]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I'm trying to set the OpenAPI spec version to 3.0 for the time being, yet neither the delegate method nor the MSBuild method proposed in the docs are working.

I need it as 3.0 for the correct OpenAPI.json file to be generated, and have tried this:

Program.cs:

builder.Services.AddOpenApi(options =>
{
    options.OpenApiVersion = OpenApiSpecVersion.OpenApi3_0;
});

BackendService.csproj:

  <PropertyGroup>
    <OpenApiDocumentsDirectory>.</OpenApiDocumentsDirectory>
  </PropertyGroup>
  <ItemGroup>
    <OpenApiGenerateDocumentsOptions Include="Options">
      <Options>--openapi-version OpenApi3_0</Options>
    </OpenApiGenerateDocumentsOptions>
  </ItemGroup>

Yet the generated OpenAPI.json is always version 3.1:
OpenAPI.json:

  "openapi": "3.1.1",
  "info": {
    "title": "BackendService | v1",
    "version": "1.0.0"
  }

Any suggestions gladly appreciated!

Expected Behavior

No response

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version

.NET 10

Anything else?

No response

[captainsafia]

@Zylvian Are you seeing the correct version when you visit the /openapi/{documentName}.json endpoint in the browser?

Can you try setting <OpenApiGenerateDocumentsOptions>--openapi-version OpenApi3_1</OpenApiGenerateDocumentsOptions> directly in your config? I suspect something might be off with the options pattern that you are using.

[Zylvian]

@Zylvian Are you seeing the correct version when you visit the /openapi/{documentName}.json endpoint in the browser?

Can you try setting <OpenApiGenerateDocumentsOptions>--openapi-version OpenApi3_1</OpenApiGenerateDocumentsOptions> directly in your config? I suspect something might be off with the options pattern that you are using.

For the latter, could you specify how and where in the config you want it placed? In the same ItemGroup?

[desjoerd]

@Zylvian you should set the <OpenApiGenerateDocumentsOptions> in a <PropertyGroup>.

<PropertyGroup>
  <OpenApiDocumentsDirectory>.</OpenApiDocumentsDirectory>
  <OpenApiGenerateDocumentsOptions>--openapi-version OpenApi3_0</OpenApiGenerateDocumentsOptions>
</PropertyGroup>

[Zylvian]

@Zylvian you should set the <OpenApiGenerateDocumentsOptions> in a <PropertyGroup>.

. --openapi-version OpenApi3_0

This did cause the document to state the correct version at the top:

{
  "openapi": "3.0.4",
  "info": {
    "title": "BackendService | v1",
    "version": "1.0.0"
  },

However, the format of its output is still in accordance with the 3.1 spec, not the 3.0 spec.

Previous .NET 9 output:

.NET 10 (OpenAPI 3.1) output:

Specifically, the new schema is generating regex patterns for doubles.

[desjoerd]

The underlying package Microsoft.OpenApi handles the downcasting from Openapi 3.1 to 3.0. Could you raise an issue there?

https://github.com/microsoft/OpenAPI.NET

[desjoerd]

The pattern output could be because of the NumberHandling on the json options.

You could try to set it to Strict.

builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.NumberHandling = JsonNumberHandling.Strict;
});