Why do I get the error: 82: Invalid variable name. Must start with a letter but was: ‘proguard

Question

When following the steps at https://developer.android.com/studio/build/gradle-tips#remove-private-signing-information-from-your-project, I get the following error and the Cordova Android app does not build:

/platforms/android/build.gradle': 82: Invalid variable name. Must start with a letter but was: ‘proguard

Line 82 is:

proguardFiles getDefaultProguardFile(‘proguard-android.txt’), ‘proguard-rules.pro’

I don't know what the error is referring to. I don't see any variables beginning with anything other than letters. The build.gradle file includes:

// Creates a variable called keystorePropertiesFile, and initializes it to the
// keystore.properties file.
def keystorePropertiesFile = rootProject.file("keystore.properties")

// Initializes a new Properties() object called keystoreProperties.
def keystoreProperties = new Properties()

// Loads the keystore.properties file into the keystoreProperties object.
keystoreProperties.load(new FileInputStream(keystorePropertiesFile))

// https://developer.android.com/studio/build/gradle-tips#remove-private-signing-information-from-your-project

android {
  buildTypes {

  signingConfigs {
    config {
      keyAlias keystoreProperties['keyAlias']
      keyPassword keystoreProperties['keyPassword']
      storeFile file(keystoreProperties['storeFile'])
      storePassword keystoreProperties['storePassword']
    }
  }
//  you will normally want to enable ProGuard only for your release
//  builds, as it’s an additional step that makes the build slower and can make debugging more difficult

    release {
      minifyEnabled true
      proguardFiles getDefaultProguardFile(‘proguard-android.txt’), ‘proguard-rules.pro’
    }
  }
} 

Answer 1

The problem is the curly quotes in ‘proguard-rules.pro’

Curly quotes are not recognized by Gradle, so it's enough to change them to normal single quotes: 'proguard-rules.pro'.

Most occurrences of this error are caused by weird quotes or invisible characters that can be hard to spot. They can be fixed using simple online tools:

• Curly quotes
• Invisible characters (a.k.a. Diacritics)