fix(iOS): Handle NSNull in iosCustomBrowser param for logout

[seanfar]

Description

While there isn't an issue created specifically for what this PR is attempting to address, there are a few issues that seem to be related to it.

#1061 for example, which led to the fix introduced by #1064 addressed an issue on the authorize function.

Unfortunately, the logout function is still failing to properly display the browser, causing the flow to silently fail when iosCustomBrowser is not provided, as the call to [self getCustomBrowser:NSNull] returns nil.

This seems to be happening on RN V0.77.1 with the new architecture enabled. Untested on other versions.

This PR adds a guard to fallback to the default external user agent when iosCustomBrowser is nil or NSNull.

Steps to verify

1. Configure the configuration object with no value for the iosCustomBrowser option that includes:

const config = {
  issuer: "https://youridprovider.com",
  clientId: "yourClientID",
  redirectUrl: "yourapp://callback",
  scopes: ["openid"],
  iosPrefersEphemeralSession: true,
  usePKCE: true,
};

2. Add the calls accordingly for authorize(config) and logout(config) in your code.
3. Build the app in iOS release mode.
4. Execute the authorize (login) and logout calls via your application.
5. Observe that the default browser is displayed properly.

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Name	Status	Preview	Comments	Updated (UTC)
react-native-app-auth	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 25, 2025 5:01pm

[sepperousseau]

@seanfar I tested it, it fixes the problem for me. Thanks! 👍

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[Copilot]

Pull Request Overview

This PR addresses an issue in the logout flow on iOS by ensuring that a custom browser parameter handles NSNull values appropriately.

• Adds a conditional check to verify that iosCustomBrowser is not nil or NSNull.
• Falls back to the default external user agent when the custom browser parameter is invalid.

Comments suppressed due to low confidence (1)

packages/react-native-app-auth/ios/RNAppAuth.m:522

• Ensure that there are corresponding tests covering the scenario where iosCustomBrowser is NSNull to prevent regressions.

externalUserAgent = [self getCustomBrowser:iosCustomBrowser];

[Copilot]

[nitpick] Consider extracting the null/NSNull check for iosCustomBrowser into a helper method to improve code readability and reuse.

Suggested change

	if (iosCustomBrowser != nil && ![iosCustomBrowser isEqual:[NSNull null]]) {
	if ([self isNonNullObject:iosCustomBrowser]) {

[zibs]

Hey there @seanfar, I'm trying to reproduce the error locally but don't seem to be able too. Can you verify I'm following the right steps?

I am on a more updated RN version with new arch:

"react": "19.0.0",
"react-native": "0.79.2",

my config is;

    issuer: 'https://demo.duendesoftware.com',
    clientId: 'interactive.public',
    redirectUrl: 'io.identityserver.demo:/oauthredirect',
    additionalParameters: {},
    scopes: ['openid'] as const,
    iosPrefersEphemeralSession: true,
    usePKCE: true,

and I am running in release mode on iOS:

Screen.Recording.2025-05-27.at.10.11.28.AM.mp4

[seanfar]

Hey there @seanfar, I'm trying to reproduce the error locally but don't seem to be able too. Can you verify I'm following the right steps?

I am on a more updated RN version with new arch:

"react": "19.0.0",
"react-native": "0.79.2",

my config is;

    issuer: 'https://demo.duendesoftware.com',
    clientId: 'interactive.public',
    redirectUrl: 'io.identityserver.demo:/oauthredirect',
    additionalParameters: {},
    scopes: ['openid'] as const,
    iosPrefersEphemeralSession: true,
    usePKCE: true,

and I am running in release mode on iOS:

Hey thanks for the response and testing @zibs -

No, that seems correct. I haven't revisited this after I posted, but since then it seems the documentation for migrating to AppDelegate.swift has been added here.

My gut tells me there's likely some discrepancy between what we currently have setup in our project and what's outlined there, as we had migrated it by hand before these instructions existed. We started seeing this issue after a library + RN upgrade to 0.77.

I'll double and triple check. If it's on our end, I'll make sure to close this PR out. But if we're still seeing issues, I'll try to get you a minimal repro as soon as possible. Thank you again!

[zibs]

Sounds great, thank you!

[seanfar]

@zibs

following up as promised. After ensuring our AppDelegate.swift was setup according to the docs, it seems like this is working as expected. The issue was on our end. Apologies for any time wasted trying to repro this, I'll go ahead and close it out.

still curious how we weren't the only ones seeing this in our project, but it could very well be something similar.

cc: @sepperousseau - you may want to verify your project is setup correctly as well. Happy to help however I can.

thank you both again!