Rock The Gradle MobileEra

Transcript

Xavier F. Gouchet, Senior Software Engineer
@xgouchet
Rock the Gradle,
Rule the world

INTRODUCTION
0
A (brief) Gradle introduction

WHAT IS GRADLE ?
General Purpose
Language Agnostic
Feature Agnostic
Dependency
Management System
High performance
Build Management
Task Dependency Graph

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THE GRADLE ALGORITHM
INIT
Launches the JVM
Analyse the working directory
Creates the Project object(s)
Compiles the buildSrc module(s)
CONFIG EXEC
Executes all the build.gradle scripts
Creates & conﬁgures tasks
Resolve dependencies
Execute the relevant tasks

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BUILDSRC
1
“It’s a kind of Magic”
— Queen

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┬ MyProject
├┬ app/
│├── src/
│└── build.gradle
├┬ buildSrc/
│├── src/
│├── build.gradle
│└── settings.gradle
├─ build.gradle
└─ settings.gradle
Project Structure

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┬ MyProject
├┬ app/
│├── src/
├┬ buildSrc/
│├── src/
├─ build.gradle
Project Structure

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┬ MyProject
├┬ app/
│├── src/
├┬ buildSrc/
│├── src/
├─ build.gradle
Project Structure

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┬ MyProject
├┬ app/
│├── src/
├┬ buildSrc/
│├── src/
├─ build.gradle
Project Structure

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Works like any module in your project
Compiled and tested before any gradle task
Groovy, Java, Kotlin, …
Any public class / method becomes available in gradle
scripts
How does it work?

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Better dependency management
Helper classes / methods
Plugin conﬁguration
Custom plugin
(Locally versioned with the project)
What can we use it for?

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⚠
“A single change in buildSrc
causes the whole project to
become out-of-date.”

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SCRIPTS
2
“Don’t repeat yourself”
— Uncle Bob Martin

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DEPENDENCIES
Write Once
Use Everywhere
https://unsplash.com/@eliabevces

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dependencies {
implementation "org.jetbrains.kotlin:kotlin-stdlib:…"
implementation "androidx.appcompat:appcompat:…"
implementation "androidx.core:core-ktx:…"
implementation "androidx.annotation:annotation:…"
}
Dependencies
app/build.gradle

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object Dependencies {
object Versions {
const val Kotlin = "1.3.50"
const val AndroidX = "1.0.0"
}
// …
}
Dependencies
buildSrc/src/main/kotlin/Dependencies.kt

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// …
object Libraries {
const val Kotlin =
"org.jetbrains.kotlin:kotlin-stdlib:${Versions.Kotlin}"
@JvmField val AndroidX = arrayOf(
"androidx.appcompat:appcompat:${Versions.AndroidX}",
"androidx.core:core-ktx:${Versions.AndroidX}",
"androidx.annotation:annotation:${Versions.AndroidX}"
)
}
}
Dependencies

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// …
object Libraries {
const val Kotlin =
)
}
}
Dependencies

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// …
object Libraries {
const val Kotlin =
)
}
}
Dependencies

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import Dependencies
dependencies {
implementation Dependencies.Libraries.Kotlin
implementation Dependencies.Libraries.AndroidX
}
Dependencies
app/build.gradle

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CONFIGURATIONS
Hide the bulk
https://unsplash.com/@adigold1

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detekt {
toolVersion = "1.0.1"
input = files("$projectDir/src/main/java")
config = files("$project.rootDir/config/detekt.yml")
reports.xml {
enabled = true
destination = file("build/reports/detekt.xml")
}
}
check.dependsOn("detekt")
Plugin Conﬁguration
app/build.gradle

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fun Project.detektConfig() {
val ext = extensions.findByType(DetektExtension::class)
ext.version = "1.0.1"
ext.input = files("$projectDir/src/main/kotlin")
// …
tasks.named("check") {
dependsOn("detekt")
}
}
buildSrc/src/main/kotlin/DetektConﬁg.kt

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// …
dependsOn("detekt")
}
}

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// …
dependsOn("detekt")
}
}

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// …
dependsOn("detekt")
}
}

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// …
dependsOn("detekt")
}
}

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import detektConfig
detektConfig()
app/build.gradle

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UTILITIES
Expand your toolbox
https://unsplash.com/@toddquackenbush

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android {
defaultConfig {
versionCode 31401
versionName "3.14.1"
}
}
Version Code & Version Name
app/build.gradle

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data class Version(
val major: Int,
val minor: Int,
val hotfix: Int
) {
val name = "$major.$minor.$hotfix"
val code = (major × 10000) + (minor × 100) + hotfix
}
buildSrc/src/main/kotlin/Version.kt

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data class Version(
val major: Int,
val minor: Int,
val hotfix: Int
) {
}

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data class Version(
val major: Int,
val minor: Int,
val hotfix: Int
) {
}

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object App {
val Version = Version(3, 14, 1)
}
buildSrc/src/main/kotlin/App.kt

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import App
android {
defaultConfig {
versionCode App.Version.code
versionName App.Version.name
}
}
app/build.gradle

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PLUGINS
3
Now you’re thinking with Plugins

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Variants
Graph
What a Plugin can do…
Tasks Extensions
Per-module conﬁgurations
Conﬁguration
Project
Task
Dependencies

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A concrete example
Sharing localisation strings between platforms

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TASK
The Core Feature
https://unsplash.com/@wanxi

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A Custom Task
open class GetStringsTask : DefaultTask() {
var languages : Array = arrayOf()
var root = ""
var baseUrl = "http://127.0.0.1"
@TaskAction fun performTask() {
for (l in languages) {
Downloader.download("$baseUrl/$l/strings.xml",
"$root/res/values-$l/strings.xml")
}
}
}
buildSrc/src/main/kotlin/GetStringsTask.kt

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A Custom Task
var root = ""
}
}
}

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A Custom Task
var root = ""
}
}
}

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A Custom Task
var root = ""
}
}
}

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A Custom Task
var root = ""
}
}
}

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A Custom Task
import GetStringsTask
task downloadStrings(type: GetStringsTask) {
languages = ["en", "fr"]
root = "$projectDir/src/main"
baseUrl = "https://example.org/locales"
}
app/build.gradle

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EXTENSION
Adding some
ﬂexibility
https://unsplash.com/@glenncarstenspeters

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A Custom Extension
open class GetStringsExt(
var languages: Array = arrayOf(),
var baseUrl: String = "http://127.0.0.1"
)
buildSrc/src/main/kotlin/GetStringsExt.kt

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A Custom Extension
var root = ""
var extension = GetStringsExt()
for (l in extension.languages) {
val url = "${extension.baseUrl}/$l/strings.xml"
val path = "$root/res/values-$l/strings.xml"
Downloader.download(url, path)
}
}
}

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A Custom Extension
var root = ""
}
}
}

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A Custom Extension
var root = ""
}
}
}

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A Custom Extension
var root = ""
}
}
}

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A Custom Extension… and a Plugin
class GetStringsPlugin : Plugin {
override fun apply(project: Project) {
val ext = project.extensions
.create("getStrings", GetStringsExt::class.java)
val task = project.tasks
.create("getStrings", GetStringsTask::class.java)
task.apply {
root = "${project.projectDir.path}/src/main"
extension = ext
}
}
}
buildSrc/src/main/kotlin/GetStringsPlugin.kt

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task.apply {
extension = ext
}
}
}

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task.apply {
extension = ext
}
}
}

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task.apply {
extension = ext
}
}
}

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task.apply {
extension = ext
}
}
}

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task.apply {
extension = ext
}
}
}

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import GetStringsPlugin
apply plugin: GetStringsPlugin
getStrings {
languages = ["en", "fr"]
// no need to specify the root path anymore
}
app/build.gradle

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The extension makes it easy to conﬁgure
The plugin can ﬁll in properties automatically
The plugin can generate tasks per variant
The plugin can manipulate the graph
Why use a Plugin+Extension

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GOING FURTHER
4
“Don't stop me now (cause I’m having a good time!)”
— Queen

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TASK GRAPH
Where the
Magic happen
https://unsplash.com/@bill_oxford

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Ordering Tasks
// …
project.afterEvaluate { p ->
p.tasks
.withType(GenerateResValues::class.java) {
it.dependsOn(task)
}
}
}
}

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Ordering Tasks
// …
p.tasks
it.dependsOn(task)
}
}
}
}

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Ordering Tasks
// …
p.tasks
it.dependsOn(task)
}
}
}
}

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SIDENOTE ON TASK ORDER
STRICT
A.dependsOn(B)
C.finalizedBy(B)
LOOSE
D.mustRunAfter(B)
E.shouldRunAfter(B)

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LOOSE
D.mustRunAfter(B)
E.shouldRunAfter(B)
$ gradle D
> Task :app:D
BUILD SUCCESSFUL in 4s
1 task executed

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LOOSE
D.mustRunAfter(B)
E.shouldRunAfter(B)
$ gradle D B
> Task :app:B
> Task :app:D
2 tasks executed

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LOOSE
D.mustRunAfter(B)
E.shouldRunAfter(B)
$ gradle E
> Task :app:E
1 task executed

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LOOSE
D.mustRunAfter(B)
E.shouldRunAfter(B)
$ gradle E B
> Task :app:B
> Task :app:E
2 tasks executed

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LOOSE
D.mustRunAfter(B)
E.shouldRunAfter(B)
B.dependsOn(A)
A.dependsOn(E)
$ gradle E B
> Task :app:E
> Task :app:A
> Task :app:B
3 tasks executed

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PLUGIN INTEGRATION
Help the developer
use your Plugin
https://unsplash.com/@momentsbygabriel

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Aliasing the Plugin
apply plugin: "java-gradle-plugin"
gradlePlugin {
plugins {
getStrings {
id = "getStrings" // the alias
implementationClass = "GetStringsPlugin"
}
}
}
buildSrc/build.gradle

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Aliasing the Plugin
import GetStringsPlugin
apply plugin: GetStringsPlugin
app/build.gradle

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Aliasing the Plugin
apply plugin: "getStrings"
app/build.gradle

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Task’s group & description
init {
group = "mobileEra"
description = "Downloads strings.xml from server."
}
// …
}

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Android tasks
-------------
androidDependencies - Displays the Android dependencies.
sourceSets - Prints out all the source sets in the project.
MobileEra tasks
---------------
getStrings - Downloads strings.xml from a server.
Verification tasks
------------------
lint - Runs lint on all variants.
$ gradlew :app:tasks

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Android tasks
-------------
androidDependencies - Displays the Android dependencies.
sourceSets - Prints out all the source sets in the project.
MobileEra tasks
---------------
getStrings - Downloads strings.xml from a server.
Verification tasks
------------------
lint - Runs lint on all variants.
$ gradlew :app:tasks

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GRADLE CACHE
Avoid
unnecessary work
https://unsplash.com/@jasonrobertsphotography

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Deﬁning Inputs & Outputs
@Input fun getLanguagesInputs(): List {
return extension.languages.toList()
}
@Input fun getBaseUrlInput(): String {
return extension.baseUrl
}
}

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@OutputFiles
fun getTaskOutputs(): List {
return extension.languages.map { l ->
File("$root/res/values-$l/strings.xml")
}
}
}

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It will never
update until we change
the conﬁg ?

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@Input
fun getDateInput() : String {
val formatter = DateTimeFormatter.ISO_DATE
return LocalDateTime.now().format(formatter)
}
}

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INCREMENTAL TASKS
Avoid
unnecessary work
https://unsplash.com/@pluyar

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Incremental Task
@TaskAction
fun incrementAction(inputs: IncrementalTaskInputs) {
if (inputs.isIncremental) {
inputs.outOfDate { println("Out of date: $it") }
inputs.removed { println("Removed: $it") }
} else {
// …
}
}
}

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