chenguandong / android-nologs-plugin

Removes logs from android application built with Gradle & Android New Build System

NoLogs plugin

Removes logs completely from project before compillation, then brings them back.

Plugin is designed for Android apps that are built with Gradle and Android New Build System.

Why do I need this?

Release builds of Android applications should not contain any debug logs.

One of the approaches of removing Android logs in production is the following

if (BuildConfig.DEBUG) {
    Log.d("TAG", "Some log");
} 

This works pretty well but you must always add an extra if statement.

Another approach if to remove logs with the following Proguard rule:

-assumenosideeffects class android.util.Log {
    public static boolean isLoggable(java.lang.String, int);
    public static int v(...);
    public static int i(...);
    public static int w(...);
    public static int d(...);
    public static int e(...);
}

This removes simple logs completely, but converts more complex logs (assuming width and height are fields of a class)

Log.d("TAG", "width: " + width + "; height: " + height);

to something like

new StringBuilder("width: ").append(this.b).append("; height: ").append(this.c);

So, Log methods are removed, but the strings are left in the code.

Setup

Apply plugin:

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        // apply android gradle plugin here
        
        // Version may change, see the latest version on jcenter
        classpath 'com.roottony.gradle:nologs:0.9'
    }
}
apply plugin: 'com.roottony.nologs'

Note that this plugin must be applied after

apply plugin 'com.android.application' 

or

apply plugin 'com.android.library'

Set what to remove

To remove calls of all android.util.Log methods, add this to build.gradle

nologs {
    logClass = 'Log'
}

If you have your own logging class, add it instead

nologs {
    logClass = 'MyLoggingClass'
}

Select whether logs should be removed for particular variant with the following closure

nologs {
    shouldRemoveLogs = { variant ->
        return variant.buildType.name == 'release'
    }
}

Other options

Disable plugin completely with

nologs {
    enabled = false
}

Disable uncommenting logs (useful to understand what's happeing under the hood)

nologs {
    disableUncomment = true
}

How does it work?

No magic, just a regexp.

Before compillation occurs, all java source files are processes with the regexp

'^\ *' + logClass + '\.[\s\S]+?(?=\)\ *;\ *$)\)\ *\;'

After compilation completes, java source files are processed with another regexp

'\ *' + logClass + '\.[\s\S]+?(?=\)\ *;\ *)\)\ *\;'

where logClass is the name of the class you specified.

See the details in the source code.

Is it safe?

Well, almost :)

Dangerous code constructions are:

if (someCondition)
    MyLogClass.d("Some log");
    
doSomethingElse();

as doSomethingElse() call will be removed. Note that

if (someCondition) MyLogClass.d("Some log");
    
doSomethingElse();

is OK as if (someCondition) MyLogClass.d("Some log"); line will not be touched at all.

In general, a log will not be removed if it is not the first statement in the line:

doSomethingElse(); MyLogClass.d("Some log");