Gradle deep dive Bryan Herbst Android Engineer @ Target

The toolchain and you

Your Code

Your Code (it’s just text)

Build tools

Gradle

IDE

Your Code Build tools Gradle IDE

Why Gradle?

Reproducible builds !

Dependency Management "

Extensibility #

Faster builds $

Task automation %

Other options Bazel and Buck

Gradle intro

Projects Every build contains 1+ projects

Projects Every build contains 1+ projects compile ':projectB:childC'

Tasks Every project contains 1+ tasks

Build lifecycle Initialization Configuration Execution

Gradle Wrapper It isn’t that special

if (gradleIsNotInstalled) { installGradle() } invokeGradle()

Why?

Why? For consistent builds across machines

Tasks Things you can do

Android Tasks • androidDependencies - Displays the Android dependencies of the project. • signingReport - Displays the signing info for each variant. • sourceSets - Prints out all the source sets defined in this project. • assemble - Assembles all variants of all applications and secondary packages. • assembleAndroidTest - Assembles all the Test applications. • assembleDebug - Assembles all Debug builds. • assembleRelease - Assembles all Release builds. • build - Assembles and tests this project. • buildDependents - Assembles and tests this project and all projects that depend on it. • buildNeeded - Assembles and tests this project and all projects it depends on. • clean - Deletes the build directory. • cleanBuildCache - Deletes the build cache directory. • compileDebugAndroidTestSources • compileDebugSources • compileDebugUnitTestSources • compileReleaseSources • compileReleaseUnitTestSources • mockableAndroidJar - Creates a version of android.jar that's suitable for unit tests. • init - Initializes a new Gradle build. • wrapper - Generates Gradle wrapper files. • buildEnvironment - Displays all buildscript dependencies declared in root project 'HelloWorld'. • components - Displays the components produced by root project 'HelloWorld'. [incubating] • dependencies - Displays all dependencies declared in root project 'HelloWorld'. • dependencyInsight - Displays the insight into a specific dependency in root project 'HelloWorld'. • dependentComponents - Displays the dependent components of components in root project 'HelloWorld'. [incubating] • help - Displays a help message. • model - Displays the configuration model of root project 'HelloWorld'. [incubating] • projects - Displays the sub-projects of root project 'HelloWorld'. • properties - Displays the properties of root project 'HelloWorld'. • tasks - Displays the tasks runnable from root project 'HelloWorld' (some of the displayed tasks may belong to subprojects). • installDebug - Installs the Debug build. • installDebugAndroidTest - Installs the android (on device) tests for the Debug build. • uninstallAll - Uninstall all applications. • uninstallDebug - Uninstalls the Debug build. • uninstallDebugAndroidTest - Uninstalls the android (on device) tests for the Debug build. • uninstallRelease - Uninstalls the Release build. • check - Runs all checks. • connectedAndroidTest - Installs and runs instrumentation tests for all flavors on connected devices. • connectedCheck - Runs all device checks on currently connected devices. • connectedDebugAndroidTest - Installs and runs the tests for debug on connected devices. • deviceAndroidTest - Installs and runs instrumentation tests using all Device Providers. • deviceCheck - Runs all device checks using Device Providers and Test Servers. • lint - Runs lint on all variants. • lintDebug - Runs lint on the Debug build. • lintRelease - Runs lint on the Release build. • test - Run unit tests for all variants. • testDebugUnitTest - Run unit tests for the debug build. • testReleaseUnitTest - Run unit tests for the release build. •

(Some) Android Tasks • assembleDebug – Assembles all Debug builds. • assemble – Assembles all variants of all applications and secondary packages. • clean – Deletes the build directory

(Some) Android Tasks • assembleDebug – Assembles all Debug builds. • assemble – Assembles all variants of all applications and secondary packages. • clean – Deletes the build directory

(Some) Android Tasks • assembleDebug – Assembles all Debug builds. • assemble – Assembles all variants of all applications and secondary packages. • clean – Deletes the build directory

task hello { doLast { println 'Hello world!' } }

doFirst() doLast()

doFirst() Add to the beginning of the action list doLast()

doFirst() Add to the beginning of the action list doLast() Add to the end of the action list

task hello { description 'Says hello' group 'Useless tasks' doLast { println 'Hello world!' } }

Hot off the presses (Gradle 4.2) task hello { description 'Says hello' group 'Useless tasks' doLast('Print greeting') { println 'Hello world!' } }

task taskX(dependsOn: 'taskY') { doLast { println 'taskX' } } Will run first

class GreetingTask: DefaultTask { @TaskAction fun greet() { println("Hello!") } }

Shortcuts ./gradlew tDUT = testDebugUnitTest

Shortcuts ./gradlew tDUT = testDebugUnitTest ./gradlew t = test

Shortcuts ./gradlew tDUT = testDebugUnitTest ./gradlew t = test test? tasks?

Shortcuts ./gradlew tDUT = testDebugUnitTest ./gradlew t = test ./gradlew te = test

Task Outcomes • EXECUTED- Task was fully executed

Task Outcomes • EXECUTED- Task was fully executed • UP-TO-DATE- Task inputs/outputs did not change

Task Outcomes • EXECUTED- Task was fully executed • UP-TO-DATE- Task inputs/outputs did not change • FROM-CACHE- Output pulled from cache

Task Outcomes • EXECUTED- Task was fully executed • UP-TO-DATE- Task inputs/outputs did not change • FROM-CACHE- Output pulled from cache • SKIPPED- Task was skipped

Task Outcomes • EXECUTED- Task was fully executed • UP-TO-DATE- Task inputs/outputs did not change • FROM-CACHE- Output pulled from cache • SKIPPED- Task was skipped • NO-SOURCE- Task wasn’t needed

Task Outcomes • EXECUTED - BAD • UP-TO-DATE - GOOD • FROM-CACHE - OKAY • SKIPPED - GOOD • NO-SOURCE - GOOD

Plugins

class GreetingPlugin implements Plugin { void apply(Project project) { project.task('hello') { doLast { println "Hello from the GreetingPlugin" } } } }

class GreetingPlugin implements Plugin { void apply(Project project) { project.task('hello') { doLast { println "Hello from the GreetingPlugin" } } } }

class GreetingPlugin implements Plugin { void apply(Project project) { project.task('hello') { doLast { println "Hello from the GreetingPlugin" } } } }

Anatomy of a build script

Anatomy of a Gradle build script buildscript { // ... } allprojects { // ... } apply plugin: 'kotlin' android { // ... } dependencies { // ... }

buildscript { // ... } Configuration for the Gradle build script itself allprojects { // ... } apply plugin: 'kotlin' android { // ... } dependencies { // ... }

buildscript { repositories { google() jcenter() } dependencies { classpath ’com.foo:bar:1.0.0' } } Dependency repos for the build script allprojects { // ... } apply plugin: 'kotlin' android { // ... } dependencies { // ... } Dependencies for the build script

allprojects { // ... } Configuration for this and all child projects apply plugin: 'kotlin' android { // ... } dependencies { // ... } buildscript { // ... }

allprojects { repositories { google() jcenter() } } Common dependency repo definition apply plugin: 'kotlin' android { // ... } dependencies { // ... } buildscript { // ... }

apply plugin: 'kotlin' Apply plugins android { // ... } dependencies { // ... } buildscript { // ... } allprojects { // ... }

android { compileSdkVersion 26 buildToolsVersion "26.0.1" } Plugin configuration DSL dependencies { // ... } buildscript { // ... } allprojects { // ... } apply plugin: 'kotlin'

dependencies { compile 'com.foo:bar:2.1.3' testCompile 'junit:junit:4.12' } Project dependencies buildscript { // ... } allprojects { // ... } apply plugin: 'kotlin' android { // ... }

android { compileSdkVersion 26 } android.compileSdkVersion 26 =

Configurations Dependency configurations

Configurations (Android) • debugCompile

Configurations (Android) • debugCompile • releaseCompile

Configurations (Android) • debugCompile • releaseCompile • testCompile

Configurations (Android) • debugCompile • releaseCompile • testCompile • testDebugCompile

Configurations (Android) • debugCompile • releaseCompile • testCompile • testDebugCompile • testDebugFreeBlueArmv7Compile

Custom Configurations configurations { internalCompile debugCompile.extendsFrom(internalCompile) dogfoodCompile.extendsFrom(internalCompile) } dependencies { internalCompile '...' }

Custom Configurations configurations { internalCompile debugCompile.extendsFrom(internalCompile) dogfoodCompile.extendsFrom(internalCompile) } dependencies { internalCompile '...' }

Custom Configurations configurations { internalCompile debugCompile.extendsFrom(internalCompile) dogfoodCompile.extendsFrom(internalCompile) } dependencies { internalCompile '...' }

Gradle Kotlin DSL

Static typing defaultConfig { versionCode "abc" versionName 123 multiDexEnabled "10" }

Static typing defaultConfig { versionCode "abc" versionName 123 multiDexEnabled "10" }

Autocompletion + content assist

And more! (but it is a little rough)

Organizing scripts

buildscript { // ... } ext.isCi = System.getenv().containsKey("IS_CI") task foo { doLast { if (isCi) { // ... } } }

buildscript { // ... } ext.isCi = System.getenv().containsKey("IS_CI") task foo { doLast { if (isCi) { // ... } } }

ext.supportLibVersion = "26.0.1" dependencies { compile "[…]:appcompat-v7:$supportLibVersion" compile "[…]:design:$supportLibVersion" }

Organizing scripts- include versions.gradle ext.buildTools = "26.0.1" ext.compileVersion = 26 build.gradle apply from: 'versions.gradle' android { buildToolsVersion buildTools // ... }

buildSrc Re-usable and testable buildscript code

{project}/buildSrc/ src/main/java - Plugins, tasks, etc.

{project}/buildSrc/ src/main/java - Plugins, tasks, etc. build.gradle – Dependencies and configuration

{project}/buildSrc/ src/main/java - Plugins, tasks, etc. build.gradle – Dependencies and configuration src/test/java – Tests!

See Also: github.com/android/platform_frameworks_support

Getting Build Information Knowledge is power

apply plugin: 'project-report' ./gradlew projectReport Provides: • Task report • dependency report • property report

apply plugin: 'build-dashboard' ./gradlew buildDashboard Provides: • All reports implementing the reporting interface

./gradlew [task] --profile Provides: • Build profile by step

apply plugin: 'com.gradle.build-scan' ./gradlew assembleDebug --scan Provides: • Shareable, centralized build record

Build Scans Demo

Improving Build Performance

def gitSha = 'git rev-parse --short HEAD’ .execute([], project.rootDir).text.trim()

def gitSha = 'git rev-parse --short HEAD’ .execute([], project.rootDir).text.trim() timestamp = new Date().format('yyyyMMddHHmmss')

def gitSha = 'git rev-parse --short HEAD’ .execute([], project.rootDir).text.trim() timestamp = new Date().format('yyyyMMddHHmmss') &

def gitSha = 'git rev-parse --short HEAD’ .execute([], project.rootDir).text.trim() timestamp = new Date().format('yyyyMMddHHmmss') versionNameSuffix = new Date().format('yyyyMMddHHmmss')

def gitSha = 'git rev-parse --short HEAD’ .execute([], project.rootDir).text.trim() timestamp = new Date().format('yyyyMMddHHmmss') versionNameSuffix = new Date().format('yyyyMMddHHmmss') '

Gradle Daemon Enabled by default as of Gradle 3.0

Parallel Builds

Parallel Builds org.gradle.parallel=true

Don’t compile if you don’t need to

Don’t compile if you don’t need to taskX.onlyIf { !project.hasProperty('skipX') }

Don’t compile if you don’t need to class TaskX extends DefaultTask { @Input def inputProperty }

Don’t compile if you don’t need to class TaskX extends DefaultTask { @Input def inputProperty } Task is now incremental!

Android Plugin 3.0.0 & Gradle 4.x Parallel & cacheable

Configurations compile

Configurations compile testCompile

Configurations compile testCompile debugCompile

Configurations compile testCompile debugCompile apk

Configurations compile testCompile debugCompile apk provided

Configurations compile testCompile debugCompile apk provided

Configurations implementation Available at compile time, Only available to consumers at runtime

Configurations implementation api Available at compile time and run time

Configurations implementation api compileOnly Only available at compile time

Configurations implementation api compileOnly runtimeOnly Only available at runtime

Lib B Lib A App

Lib B Lib A App Old configurations Change (recompile)

Lib B Lib A App Old configurations Change (recompile) recompile

Lib B Lib A App Old configurations Change (recompile) recompile recompile

Lib B Lib A App New configurations Change (recompile) recompile implementation

Plugin 2.2.0 Gradle 2.14.1 Plugin 3.0 Gradle 4.0 Configuration ~2 mins ~2.5 s 1-line Java change ~2 mins 15 s ~6.4 s

Build cache

Build cache (not Android’s)

Has input changed?

Has input changed? UP-TO-DATE

Has input changed? UP-TO-DATE In cache?

Has input changed? UP-TO-DATE In cache? Yes FROM-CACHE

Has input changed? UP-TO-DATE In cache? Yes FROM-CACHE Execute task

Build cache org.gradle.caching=true Or ./gradlew [task] --build-cache

Resources • google.github.io/android-gradle-dsl • github.com/android/platform_frameworks_support • gradle.org/docs