Faulty log message for Authority configuration

[FrodeAtSea]

Microsoft.Identity.Web Library

Microsoft.Identity.Web

Microsoft.Identity.Web version

4.3.0

Web app

Sign-in users and call web APIs

Web API

Protected web APIs (validating tokens)

Token cache serialization

In-memory caches

Description

Log message

Microsoft.Identity.Web.MergedOptions [ 500 ]
 [MsIdWeb] Authority 'https://X.ciamlogin.com/X.onmicrosoft.com' is being ignored because Instance 'https://X.ciamlogin.com' and/or TenantId 'X.onmicrosoft.com' are already configured. 
To use Authority, remove Instance and TenantId from the configuration.

reported, even if there is no Instance and TenantId configured.

Reproduction steps

1. Follow instructions to set up a Web App with Entra external Id (external tenant).
2. Be sure the appsettings.json resemble

  "AzureAd": {
    "Authority": "https://X.ciamlogin.com/",
    "ClientId": "an id",
    "ClientCertificates": [
      {
        "SourceType": "StoreWithThumbprint",
        "CertificateStorePath": "CurrentUser/My",
        "CertificateThumbprint": "a thumbprint"
      }
    ],
    "ResponseType": "code",
    "CallbackPath": "/signin-oidc",
    "SignedOutCallbackPath": "/signout-callback-oidc"
  },

Error message

Id Web logs

Microsoft.Identity.Web.MergedOptions [ 500 ]
[MsIdWeb] Authority 'https://X.ciamlogin.com/X.onmicrosoft.com' is being ignored because Instance 'https://X.ciamlogin.com' and/or TenantId 'X.onmicrosoft.com' are already configured.
To use Authority, remove Instance and TenantId from the configuration.

Relevant code snippets

builder.Services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
         .AddMicrosoftIdentityWebApp(builder.Configuration.GetSection("AzureAd"))
         .EnableTokenAcquisitionToCallDownstreamApi() // required for Oidc Authorization Code flow
         .AddInMemoryTokenCaches();

Regression

No response

Expected behavior

No log message, or a log/error specifying the problem with Authority configuration.

[jmprieur]

@bgavrilMS : would this PR fix it?
#3617

When the authority parsing is available in MSAL, I would recommend you merge it. It has good value, in particular the doc part

[bgavrilMS]

Yes, it would fix it.

[FrodeAtSea]

@bgavrilMS : would this PR fix it? #3617

I guess the documentation for External ID in external tenants - Configure the application for authentication should be corrected likewise regarding the Authority format for External tenant.