Modify proguard rules in a managed expo project

README.md

Modify proguard rules in a managed expo project

If you ever need to modify the proguard rules for the Android-part of your Expo managed workflow, you can achieve this by using a config plugin.

1. Make a folder for config-plugins called ./plugins in the project root folder.
2. Place the withProguardRules.js and my-proguard-rules.pro in the folder
3. Add the config plugin to the plugins array of your app.config.js (or app.json if you're using that instead).

NOTE: if you rename your .pro file, don't forget to change the two occurrences of my-proguard-rules in withProguardRules.js as well.

Attribution

This solution was inspired by the detox config-plugin

app.config.js

export default {
  expo: {
    name: "My Project",
    // ...
    plugins: [
      "./plugins/withProguardRules",
      // ...
    ],
    
  },
};

my-proguard-rules.pro

-keep class com.swmansion.reanimated.** { *; }
-keep class com.facebook.react.turbomodule.** { *; }

withProguardRules.js

const { createRunOncePlugin,  withAppBuildGradle } = require("@expo/config-plugins");
const pkg = require("../package.json");

const withProguardRules = (config) => {
  return withAppBuildGradle(config, (config) => {
    if (config.modResults.language === "groovy") {
      config.modResults.contents = addProguardRules(config.modResults.contents);
    } else {
      throw new Error(
        "Cannot add to maven gradle because the project build.gradle is not groovy"
      );
    }
    return config;
  });
};

function addProguardRules(buildGradleContent) {
  const RE_EXISTS = /my-proguard-rules\.pro/g;
  if (RE_EXISTS.test(buildGradleContent)) {
    return buildGradleContent;
  }

  const RE_ENTRY = /proguardFiles getDefaultProguardFile\("proguard-android.txt"\),\s?"proguard-rules.pro"/;

  if (!RE_ENTRY.test(buildGradleContent)) {
    throw new Error(
      "Cannot add to maven gradle because the proguard regex could not find the entrypoint row"
    );
  }

  return buildGradleContent.replace(
    RE_ENTRY,
    `proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"

            // Project-specific additions to proguard
            def myProguardRulesPath = new File(["node", "--print", "require.resolve('expo/package.json')"].execute(null, rootDir).text.trim(), "../plugins/my-proguard-rules.pro")
            proguardFile(myProguardRulesPath)
            
            `
  );
}

module.exports = createRunOncePlugin(
  withProguardRules,
  `${pkg.name}-withProguardRules`,
  pkg.version
);