feat: Add a config plugin for Expo (iOS & Android)

[aurelien-iapp]

Fixes N/A

Description

This patch adds a new plugin directory with an Expo config plugin.

This plugin will automatically patch the iOS Objective-C code to perform the different steps described in the README:

• it adds protocol conformance to RNAppAuthAuthorizationFlowManager to the AppDelegate
• it creates a new authorizationFlowManagerDelegate property
• it patches application:openURL:options: to handle the custom-scheme based redirects
• it patches application:continueUserActivity:restorationHandler: to handle the deep (universal) link redirects

⚠️ to patch the AppDelegate.h it leverages withDangerousMod and the "codeMod" API, which are not stable (but everybody uses them and we don't really have a choice here...)

Steps to verify

1. create a new Expo project (any template will do)
2. add react-native-app-auth to the project: you can point to my branch for testing purposes:

   "dependencies": {
       "react-native-app-auth": "aurelien-iapp/react-native-app-auth#expo-config-plugin",
       ...

3. add the plugin to your app.json's "plugins" section:

   "plugins": [
       "react-native-app-auth/plugin"
       ...

4. Generate the iOS/Android projects using npx expo prebuild and check the contents of AppDelegate.mm and AppDelegate.h. Changes will be visible as follows:

[merijnhofsteenge]

Hello,

Thanks for making this plugin. My team is planning on using it. Do you have any information on whether this will be merged into the repo at some point?

[zibs]

Hey @merijnhofsteenge and @aurelien-iapp -- just trying to get a sense of your use case here? Why would you be wanting to use this library as opposed to Expo's AuthSession library if you're already using Expo?

[merijnhofsteenge]

Hey @zibs. My company also has native apps connecting to the same OAuth client. The native developers recommended using AppAuth. It seems however that Expo's AuthSession can do the same, so we will explore this route now. Thank you for your question!

[Off2Race]

Hi, @zibs – I'm curious about the status of this PR. Will it be merged at some point? If so, I'd love to use the capability.

Regarding your question about the use case, we have an existing app that uses react-native-app-auth, mostly with the Google provider, but we've experimented with others, particularly Strava. The functionality works great. The app has been in production for 3 years now. Originally, our app didn't use Expo but we've recently tried to add it, including the use of Continuous Native Generation (CNG), where the expo prebuild command is used to generate everything in the ios and android folders. We like this concept but ran into an issue with cases like this library which requires manually updates to the native files. Expo's solution to that issue is the development of a plug-in, which is addressed by this PR. It's certainly possible that we could use Expo's AuthSession to provide the same functionality but we'd prefer to not make the switch as the current functionality works great.

Until I found this PR, we were considering developing our own plug-in but I'm pleased to see that someone already did the work. Many thanks to the library maintainers for such a great package. @zibs, let me know your thoughts on the merge.

[carbonrobot]

@aurelien-iapp @Off2Race
We will set an internal meeting next week to discuss the implications of merging and maintaining this plugin.

[aurelien-iapp]

Hey guys,
I'm quite surprised to see activity on such an old PR 😃

@Off2Race I used this plugin to setup a custom OAUTH sign-in for a client project about a year ago, and didn't have much feedback at the time so I deduced it was not a priority for the team.

About your remarks:

• I made the code for the android app: it's on a private repo but I can definitely publish this part if you're interested
• I recently upgraded the aforementioned project to the latest Expo SDK and had no issue with the plugin code, so apart form the dependencies it should work as-of

Tell me if you are still interested and I will prepare the patch for Android.

Regards !

[carbonrobot]

@aurelien-iapp Appreciate the contribution, we would love to see the android code as well. We had some maintainers leave and our native libraries were harder to maintain without community support, but we have been able to dedicate some more resources to this one recently.

[carbonrobot]

@aurelien-iapp Thanks for the update, we will merge this and restructure the code so we can publish it on NPM. Could you fix the merge conflicts on your side? I would really like to keep your username as the original contributor on the commits so your work is captured here.

[aurelien-iapp]

@aurelien-iapp Could you fix the merge conflicts on your side?

Hello guys 👋
Yes I will rebase and add the Android files today, I didn't have a minute for myself this week sorry 🙏

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Name	Status	Preview	Comments	Updated (UTC)
react-native-app-auth	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 6, 2024 0:38am

[aurelien-iapp]

I did rebase de branch, move the plugin dir into packages/react-native-app-auth/plugin and did some minor changes (see the commits for details).
Right now the plugin:

For iOS:

• inserts some new imports into AppDelegate.h
• adds protocol conformance to the AppDelegate class
• declares the authorizationFlowManagerDelegate property
• updates application:openURL:options:'
• updates application:continueUserActivity:restorationHandler:

which makes the complete setup for RN>=0.68 as per the docs

on Android:

• it adds the appAuthRedirectScheme declaration to app/build.gradle

IMPORTANT NOTES:

• this plugin cannot "guess" the scheme needed to generate the Android modifications and will crash – with a message – unless provided with an authScheme parameter: this means it must be declared as follows in the app.json at the root of the Expo project:

   {
     "expo": {
        ...
        "plugins": [
          [ "react-native-app-auth/plugin", { "authScheme": "my.redirect.scheme.goes.here" }],
          ...
        ]

• on iOS declaring the scheme in app.json will suffice (not on Android since Expo does it differently...)
• as of now the Android part of the plugin (and only this one) is not re-entrant: you cannot "prebuild" again without cleaning. I could definitely improve this when I have the time but as of today this is good enough for my use cases
• the docs have completely changed and I don't really know where to detail all these steps... so if someone knowledgeable could put a word about it somewhere it would be great 😄