7-How-to-Safely-Build-Assigned-Flutter-App-with-GitHub-Actions

build.gradle

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}

def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
    flutterVersionCode = '4'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '4.1.0'
}

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

def keystoreProperties = new Properties()
def keystorePropertiesFile = rootProject.file('key.properties')
if (keystorePropertiesFile.exists()) {
    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}


android {
    compileSdkVersion 30

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }

    lintOptions {
        disable 'InvalidPackage'
    }

    defaultConfig {
        applicationId "your-applicationid.com"
        minSdkVersion 16
        targetSdkVersion 30
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }

    signingConfigs {
        release {
            //From decoded key
            storeFile = file('key.jks')
            //From key.properties
            keyAlias keystoreProperties['keyAlias']
            keyPassword keystoreProperties['keyPassword']
            storePassword keystoreProperties['storePassword']
        }
    }

    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.release
        }
    }
}

flutter {
    source '../..'
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}

ci-cd.yml

name: CI/CD

on:
  push:
    branches:
      - develop
      - master
    pull_request:
      branches:
        - develop
        - master

env:
  JAVA_VERSION: "11.x"
  FLUTTER_VERSION: "2.2.3"
  FLUTTER_CHANNEL: "stable"
  PROPERTIES_PATH: "./android/key.properties"

jobs:
  flutter_test:
    name: Run Flutter assigned build appbundle
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: actions/setup-java@v1
        with:
          java-version: ${{env.JAVA_VERSION}}
      - uses: subosito/flutter-action@v1
        with:
          channel: ${{env.FLUTTER_CHANNEL}}
          flutter-version: ${{env.FLUTTER_VERSION}}

      # Creating the key.properties file
      - run: |
          echo keyPassword=\${{ secrets.KEY_STORE }} > ${{env.PROPERTIES_PATH}}
          echo storePassword=\${{ secrets.KEY_PASSWORD }} >> ${{env.PROPERTIES_PATH}}
          echo keyAlias=\${{ secrets.KEY_ALIAS }} >> ${{env.PROPERTIES_PATH}}

      # Decoding base64 key into a file
      - run: echo "${{ secrets.KEYSTORE2 }}" | base64 --decode > android/app/key.jks

      # Get dependencies and make assigned appbundle
      - run: | 
          flutter pub get
          flutter build appbundle

      # Make appbundle downloadable
      - name: Upload artefato
        uses: actions/upload-artifact@v2
        with:
          name: appbundle
          path: build/app/outputs/bundle/release

Take a look at How to Safely Build Assigned Flutter App with GitHub Actions post

echo keyPassword=\${{ secrets.KEY_STORE }} > ${{env.PROPERTIES_PATH}}

why do you need to put \ after = ?
my build fails here saying:
line 2: syntax error near unexpected token )'`

maybe because I have these characters KEY_STORE

The backslash b4 the = is for escaping the subsequent character.
Are u changing something? I've never had your problem.

yes, I ended up restoring the whole key.properties from base64, similar to how you did key.jks
so instead of 4 concatenating lines I have one,

Thank you for this snippet though, after some adjustment I get it building in CI

Good for u!