Sudden Error: Cannot read properties of null (reading 'swaggerUIRedirectOauth2')

[maxstue]

Hey,

I use swaggerUI for a company project i work for and until last week or so it worked fine, but suddenly I get an error after the redirect Uncaught TypeError: Cannot read properties of null (reading 'swaggerUIRedirectOauth2') at run (oauth2-redirect.html)

We use AzureAD/Entra and when I click on the "Authorize"-Button on the swagger site it opens a new tab in my browser where I can log into Azure and that works but when redirecting it shows me a blank page with the shown error in the console.

Am I doing something wrong here ? Can someone help me please ? :)

My code:

        services.AddOpenApi("openapi", opt =>
		{
		 opt.AddDocumentTransformer((document, _, _) =>
        {
            document.Info = new()
            {
				//...
            };
            opt.AddDocumentTransformer<BearerAuthSchemeTransformer>();
            return Task.CompletedTask;
        }}
	));

public sealed class BearerAuthSchemeTransformer(IAuthenticationSchemeProvider authenticationSchemeProvider, IConfiguration configuration)
    : IOpenApiDocumentTransformer
{
    public async Task TransformAsync(OpenApiDocument document, OpenApiDocumentTransformerContext context, CancellationToken cancellationToken)
    {
        var appSettings = configuration.GetSection(SharedSettings.AzureAdPath).Get<AzureAdSettings>();
		//...

        var authenticationSchemes = await authenticationSchemeProvider.GetAllSchemesAsync();
        if (authenticationSchemes.Any(authScheme => authScheme.Name == "Bearer"))
        {
            var requirements = new Dictionary<string, OpenApiSecurityScheme>
            {
                ["Bearer"] = new()
                {
                    Type = SecuritySchemeType.OAuth2,
                    Flows = new()
                    {
                        AuthorizationCode = new()
                        {
                            AuthorizationUrl =
                                new($"{appSettings.Instance}{appSettings.TenantId}/oauth2/v2.0/authorize"),
                            TokenUrl = new($"{appSettings.Instance}{appSettings.TenantId}/oauth2/v2.0/token"),
                            Scopes = { { appSettings.Scopes, "Web Api access" } }
                        }
                    }
                }
            };
            document.Components ??= new OpenApiComponents();
            document.Components.SecuritySchemes = requirements;
        }
    }
}

        app.UseSwaggerUI(
            c =>
            {
                c.SwaggerEndpoint("/api/openapi.json", "Web.Api v1.0");
                c.UseRequestInterceptor("(req) => { !!window?.swaggerUIRedirectOauth2?.auth?.token?.access_token ?" +
                                        "req.headers['Authorization'] = 'Bearer ' + window?.swaggerUIRedirectOauth2?.auth?.token?.access_token" +
                                        ": undefined;" +
                                        " return req; }");

                c.OAuthClientId(appSettings?.ClientId);
                c.OAuthUsePkce();
                c.OAuthScopes(appSettings?.Scopes);
                c.DefaultModelsExpandDepth(0);
                c.DefaultModelExpandDepth(0);
                c.DocExpansion(DocExpansion.None);
                c.DocumentTitle = "SwaggerUI - Web.Api";
                c.RoutePrefix = "api/swagger";
            });

[martincostello]

• Did anything happen that precipitated this suddenly happening? For example did you upgrade any dependencies, change any configuration, or something else?
• What version of Swashbuckle.AspNetCore are you using?

[maxstue]

no nothing happened and nothing was changed in the AzureAD settings. I upgraded "Swashbuckel.Aspnetcore" from version 7.2.0 -> 8.1.1, about a month ago, but I reversed the change and that didn't do anything. That's why its so confusing 🤔

[martincostello]

Based on that description, the thing that happened was you upgrading Swashbuckle. That would have brought a new version of swagger-ui with it, and that's probably now in your browser's cache (which is probably why the revert didn't do anything).

If you want to stay on the old version, then try clearing your browser's cache. If that fixes it, then your issue is likely with swagger-ui (which we just repackage for convenience).

[maxstue]

Thanks for the fast reply, but clearing the cache didn't change anything :/

[martincostello]

Sorry then I'm not sure. Sounds like an issue with swagger-ui, which is here.

We'd need a minimal reproducible example as a GitHub repository that demonstrates the issue you're experiencing to look into this further if an issue on our end.