Can't use local .aar file inside the library module

Question

I have an aar of socialauth-android library added to my project. I've put it inside the flatDir directory as described here and it works just fine.
Now, I'm moving some of my code into the library module named commons, to reuse it in the another project. socialauth-android will be used entirely by library module, so I've moved it inside the project/commons/libs/ an rewritten my build.gradle files. From now on I can't build my project, because the following error arises:

Error:A problem occurred configuring project ':ScrollApplication'.
> Could not resolve all dependencies for configuration ':ScrollApplication:_developmentDebugCompile'.
   > Could not find :socialauth-android:.
     Searched in the following locations:
         http://dl.bintray.com/populov/maven//socialauth-android//socialauth-android-.pom
         http://dl.bintray.com/populov/maven//socialauth-android//socialauth-android-.aar
         https://oss.sonatype.org/content/repositories/snapshots//socialauth-android//socialauth-android-.pom
         https://oss.sonatype.org/content/repositories/snapshots//socialauth-android//socialauth-android-.aar
         https://repo1.maven.org/maven2//socialauth-android//socialauth-android-3.2.pom
         https://repo1.maven.org/maven2//socialauth-android//socialauth-android-3.2.aar
         file:/home/artem/Workspace/scrollandroid/libraries/socialauth-android-3.2.aar
         file:/home/artem/Workspace/scrollandroid/libraries/socialauth-android.aar
     Required by:
         scrollandroid:ScrollApplication:unspecified > scrollandroid:commons:unspecified

The error says that dependency resolver tries to find socialauth-android.aar inside the project/libraries folder which is the folder for all common libraries shared between modules of my project. But I've written in my project/commons/build.gradle file that the flatDir for the commons module is project/commons/libs! Moreover, all jar libraries contained inside the project/commons/libs/ are found during the build w/o any issues.

What can be the source of this issue?

Following are my build.gradle files (some of its code, like dependencies declarations, is dropped for brevity):

project/settings.gradle:

include ':ScrollApplication', ':commons'

project/build.gradle:

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.0.0-rc1'
    }
}

project/commons/build.gradle:

apply plugin: 'com.android.library'

repositories {
    maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' }
    mavenCentral()

    flatDir {
        dirs "libs"
    }
}

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.1"

    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 21
        versionCode 1
        versionName "1.0"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])

    compile(name:'socialauth-android', ext:'aar')
}

project/app/build.gradle:

apply plugin: 'com.android.application'

repositories {
    maven { url "http://dl.bintray.com/populov/maven" }
    maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' }

    mavenCentral()

    flatDir {
        dirs "../libraries"
    }
}

configurations {
    apt
}

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.1"

    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 21
    }

    lintOptions {
        abortOnError false
    }
}

dependencies {
    compile project(':commons')

    compile fileTree(dir: '../libraries', include: ['*.jar'])
}

Upd: project structure added

├── build.gradle
├── commons
│   ├── build.gradle
│   ├── libs
│   ├── proguard-rules.pro
│   └── src
│       ├── androidTest
│       │   └── java
│       └── main
│           ├── AndroidManifest.xml
│           ├── assets
│           ├── java
│           └── res
├── gradle
│   └── wrapper
├── libraries
│   ├── aws-android-sdk-1.7.1.1-core.jar
│   ├── aws-android-sdk-1.7.1.1-s3.jar
│   ├── libGoogleAnalyticsServices.jar
│   └── supertooltips-3.0.1.aar
├── scrollandroid-hg.iml
├── ScrollApplication
│   ├── build.gradle
│   ├── proguard.cfg
│   ├── ScrollApplication.iml
│   └── src
│       └── main
│           ├── AndroidManifest.xml
│           ├── assets
│           ├── java
│           └── res
├── settings.gradle
└── stacktrace.txt

Answer 1

It appears that the commons library is being built correctly (can you compile it separately to verify?) but the application is not. Gradle has some special rules for handling transitive dependencies (dependences nested in other dependencies) which exists since commons depends on socialauth-android.

Try adding an extra directory to the "flatDir" attribute in "project/app/build.gradle"

flatDir {
    dirs "../libraries", "../commons/libs"
}