react-native-firebase/packages/app/android/firebase-json.gradle

import groovy.json.JsonOutput
import groovy.json.JsonSlurper

String fileName = "firebase.json"
String jsonRoot = "react-native"

File jsonFile = null
File parentDir = rootProject.projectDir

for (int i = 0; i <= 3; i++) {
  parentDir = parentDir.parentFile
  jsonFile = new File(parentDir, fileName)
  if (jsonFile.exists()) break
}

if (jsonFile != null && jsonFile.exists()) {
  rootProject.logger.info ":${project.name} firebase.json found at ${jsonFile.toString()}"
  Object json = null

  try {
    json = new JsonSlurper().parseText(jsonFile.text)
  } catch (Exception ignored) {
    rootProject.logger.warn ":${project.name} failed to parse firebase.json found at ${jsonFile.toString()}."
    rootProject.logger.warn ignored.toString()
  }

  if (json && json[jsonRoot]) {
    String jsonStr = JsonOutput.toJson(JsonOutput.toJson(json[jsonRoot]))

    rootProject.ext.firebaseJson = [
      raw: json[jsonRoot],
      isFlagEnabled: { key ->
        return json[jsonRoot] != null && json[jsonRoot][key] == true
      }
    ]

    rootProject.logger.info ":${project.name} found react-native json root in firebase.json, creating firebase build config"
    android {
      defaultConfig {
        buildConfigField "String", "FIREBASE_JSON_RAW", jsonStr
      }
    }
  } else {
    rootProject.logger.info ":${project.name} firebase.json found with no react-native config, skipping"
    android {
      defaultConfig {
        buildConfigField "String", "FIREBASE_JSON_RAW", '"{}"'
      }
    }
  }
} else {
  rootProject.logger.info ":${project.name} no firebase.json found, skipping"
  android {
    defaultConfig {
      buildConfigField "String", "FIREBASE_JSON_RAW", '"{}"'
    }
  }
}