[Feature Request] Support for Expo Config Plugins

[leggomuhgreggo]

I am on a team that's fixin to start work on a cross-platform Expo app, intended to replace our three legacy clients. Wanted to inquire whether y'all would consider adding support for Config Plugins, so this library can be used with the Expo Managed Workflow (i.e. without ejecting)

Thanks for your consideration!

Feature Context

Over the past several months Expo has introduced features which enable apps to use external native modules, without ejecting Expo's managed workflow.

The customizations to the iOS and Android code that are required by a given native module are automated, using an AST-based API that Expo provides through "Config Plugins" feature.

These automations (called "mods") are executed during a new "Prebuild" phase, in which boilerplate ios and android directories are created — and then their respective files are altered, based on the instructions in a given modules config plugin. The end result is essentially the same as if you ejected and manually changed the ios/android files.

Here's the Expo blog post announcing Config Plugins and the associated feature-set.

Overview of Proposed Implementation

The process for creating a Config Plugin is detailed here:
https://docs.expo.io/guides/config-plugins/#creating-a-plugin

There are a few different "recipes" for how to implement — but the gist of it is:

• Create the app.plugin.js file, at the project root — which serves as a standard entrypoint where expo can resolve the plugin code. [ex: expo-camera]
• Export a function prefixed using "with" (eg withFeature) which accepts a config object that can be used, along with @expo/config-plugins methods, to implement mods for each platform's native code. [ex: withCamera]
• Add mods corresponding to the setup steps in your README.md
• Celebrate!

Additional Question

Are there specific feature in the RN SDK, that aren't supported in the standard React SDK? I've been trying to parse the docs a little bit but it's not totally clear to me. Thanks!

[louis-launchdarkly]

Hello @leggomuhgreggo, thank you for the feature request! While we are currently focusing on fixing some of the issues reported for React Native, we will discuss this and give you an update afterward.

[leggomuhgreggo]

Thanks @louis-launchdarkly

I wonder if, in the mean time, you might be able to offer clarification on the question:

Are there specific feature in the RN SDK, that aren't supported in the standard React SDK? I've been trying to parse the docs a little bit but it's not totally clear to me.

🙏

[louis-launchdarkly]

Hello @leggomuhgreggo, that is a good question - based on the documentation React Native and JavaScript for React, the key difference that is supported in React Native but not React are mobile specific features. The two that I know of are Monitor SDK Status and Offline Mode

[yvan33]

@louis-launchdarkly - Any update on this? We also need this in my team.
Ejecting from the Expo managed workflow is not an easy move and not preferable for us.

[erisvaldojunior]

Any news on this?

[louis-launchdarkly]

Hello @yvan33 and @erisvaldojunior, thank you for checking. Unfortunately, we are not getting to this yet, and this is still an open enhancement request in the backlog.

I should have asked earlier - is there anyone interested in making a contribution to implement this? Engineers who are familiar with the Expo will likely implement this better than us, who are not familiar with the Expo framework.

[ridafkih]

@louis-launchdarkly I got it.

Update, judging by the lack of native configuration (just Podfile) in the installation instructions on LaunchDarkly, I'm unsure if this would even require a configuration plugin at all. In contrast, when I created the ridafkih/expo-fullstory there were configuration accommodations I had to make for various .gradle files, Podfile, and in the Info.plist, which warranted the usage of an Expo Config Plugin. I created and leveraged the usage of a module I made called ridafkih/prybar in order to modify these files during the build.

In this case, since the configuration happens at runtime, there should be no problem simply installing and building your client with EAS.

In short, this would mean that for Expo users, the installation would be similar to any other non-native configured package.

Installation Steps

1. Add LaunchDarkly's SDK package with expo add launchdarkly-react-native-client-sdk
2. Build your application using EAS Build
   • For example, eas build --profile development --local
3. Profit?

At that point, you should be able to use LaunchDarkly's SDK like normal.

TL;DR

Part of EAS builds' build steps is installing Cocoapods, so installing the module using expo add launchdarkly-react-native-client-sdk and then building the client using EAS Build is enough, since none of the native files have to be modified, there is no need for any sort of Expo build configuration plugins.

If there's something I'm missing, I implore anyone here to let me know and I can create a configuration plugin to accommodate those needs. @erisvaldojunior @yvan33 @leggomuhgreggo

[neilgamb]

My team is in the same predicament... we have landed on LaunchDarkly as a feature flagging solution within a cross-platform Expo application. We would prefer not to have to eject from the Expo managed workflow at this stage in our development process. We are looking at a native modules approach to solve for this issue, but I came across this discussion and wanted to see if anyone was able to get a working solution together per @ridafkih's suggestion?

cc @leggomuhgreggo @erisvaldojunior @yvan33

Thank you

[yvan33]

@neilgamb - We were able to install launchdarkly-react-native-client-sdk directly by installing it with expo install. We are able to use LaunchDarkly perfectly fine in our Expo application.
As @ridafkih explained, there is no custom native code in the plugin so an expo config plugin is not required.

I believe this ticket can be closed.

[mjphillips-sg]

The docs should be updated to reflect this, currently it says you can't use LaunchDarkly with Expo, @louis-launchdarkly.

We're moving off Xamarin / MAUI to Expo, we'll do some testing and report back as well and hopefully confirm what @yvan33 said!

[teesloane]

@yvan33 So, LD worked out of the box for you with a managed Expo application? I've tried following the steps you provided and have been on a bit of a windy hike trying to find where to go next. I've tried it out with "expo": "~48.0.18", and "launchdarkly-react-native-client-sdk": "^7.1.5",

My main error seems to be reported here #166 : I'm getting an error throw when trying to init LD:

Code:

    useEffect(() => {
        async function initLD() {
            try {
                // Create a new instance of the LDClient and configure it with your mobile-specific SDK key and user.
                const client = new LDClient();
                const config: ld.LDConfig = {
                    mobileKey: 'API_KEY_XYZ'
                };
                const context: ld.LDContext = {
                    key: 'user-key-123abc',
                    kind: 'user'
                };
                client.configure(config, context, 5);

                await client.configure(config, context);

                // store client in state
                setLdClient(client);
            } catch (err) {
                console.error(err);
            }
        }

        initLD();
    }, []);

Error:

---

@mjphillips-sg Did you have any luck?

Thanks for any input, folks!

[yvan33]

@teesloane - Yes it worked out of the box using EAS to build the application (since it installs the native dependencies using Cocoapods).

For development, that also mean you need to build a custom dev client instead of using Expo go.

[teesloane]

@teesloane - Yes it worked out of the box using EAS to build the application (since it installs the native dependencies using Cocoapods).

For development, that also mean you need to build a custom dev client instead of using Expo go.

Thanks @yvan33 , I'll give this a shot; I had missed expo-dev-client during my research. Cheers!

[YishaiGr]

@louis-launchdarkly can you please confirm if you guys are planning to continue support expo development builds, like the developers here are mentioning that its working?
If so I would appreciate if you guys can update your docs and mention it, thanks.

[louis-launchdarkly]

Hello @YishaiGr, thank you for the question. To be accurate, with the current project, it seems that the community figures out a way to make Expo work, and there is no plan to intentionally break things. However, there is no Expo internal testing right now either, we only have testing to ensure the RN SDK still works correctly for Android and iOS.

There is a plan to work on a mostly JS-based RN SDK, and LaunchDarkly will look into supporting Expo in a better capacity then (when the installation of the LaunchDarkly RN SDK becomes simpler).

[ridafkih]

Expo Go

Expo Go is downloaded from the app store, and allows you to run Expo applications on servers or local machines by scanning the QR code, or typing the "update URL" into the Expo Go application. Since the Expo Go application is a pre-built binary, it comes pre-loaded with certain native dependencies, configurations, etc.

This means that if you want to make native customizations with Expo Go like installing the native Pods required for this library, you simply cannot.

If you are stuck using Expo Go, find another solution.

Expo Development Build

Expo has changed a lot in the past few years, and by pairing an Expo Managed Workflow with a development build, it allows you to build what is essentially your own version of the Expo Go application featuring all the customized native code, files, dependencies, and configurations your heart desires!

One of the build steps for your development build is to install Pods. This is automatically done in the managed workflow with the development build.

This means as long as you have this package installed in a managed workflow with the development build, you're good to go.

Get Started with Managed Workflow & Development Build

If you want to get started with the managed workflow and development builds, here is information from the Expo documentation. By using this pairing, you can begin using LaunchDarkly in your Expo application.

Expo Workflow Types
Development Build Introduction

[GabrielDierks]

Hey everyone just a heads up we managed to implement Launchdarkly successfully with Expo. Essentially there were no extra steps needed for our product that is using a Development build via prebuild. The only fix we had to do was to move the "expo-dev-client" package to the devDependencies because otherwise requests wouldn't go through for android!

"expo": "^49.0.11",
"react-native": "^0.72.5",
"launchdarkly-react-native-client-sdk": "^8.0.1",

[rgommezz]

I am still struggling with Android, see #227 (comment)

[louis-launchdarkly]

We have taken the request in mind for the development of the next LaunchDarkly React Native SDK - https://github.com/launchdarkly/js-core/tree/main/packages/sdk/react-native is currently in alpha, written in pure JavaScript, and supports Expo 49/RN 0.72.x. If you are interested, we would love to get some feedback before moving this 10.x SDK to GA.

Because the 10.x written in pure JavaScript, which should remove the need to have Expo Config Plugin. Please let us know if there are other reasons that this plugin will still be desirable in the next version.

[leggomuhgreggo]

Would this support web?

[yusinto]

The react-native SDK has been re-written and released. The new version v10 is purely in TypeScript and supports Expo. At this time we support iOS and Android only.

Please consider upgrading to that new version to fix this issue. Thank you for your patience.

[github-actions]

This issue is marked as stale because it has been open for 30 days without activity. Remove the stale label or comment, or this will be closed in 7 days.