Taming the Kotlin Compiler (Droidcon TO 2019)

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Taming the Kotlin Compiler

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$ git log commit 59da358e7aef1109fb71d964f846e9dcb61517c6 Author: Matt Precious <…@squareup.com> Date: Fri Nov 10 10:47:32 2017 Activity contact header tweaks $ find . -name *.java | wc -l 1122 $ find . -name *.kt | wc -l 330

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$ git log commit c9ba9967bfdb3cdde63a336ef91001040b57fed0 Author: Andrew Tran <…@squareup.com> Date: Fri Nov 8 15:04:30 2019 Updating selection blocker to respect help items $ find . -name *.java | wc -l 209 $ find . -name *.kt | wc -l 2611

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for(i in 1..N) {a // write N java files }a

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for(i in 1..N) {a val javaclassfile = File(javaSourcesDir, "JavaTemp$i.java") javaclassfile.use {bout -> out.println("class JavaTemp$i {}") }b }a

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for(i in 1..N) {a val javaclassfile = File(javaSourcesDir, "JavaTemp$i.java") javaclassfile.use {bout -> out.println("class JavaTemp$i {}") }b val process = ProcessBuilder() .command("time", "javac", "…") .start() val timeOutput = process.errorStream.use(BufferedReader::readLine) val tokens = timeOutput.split("\\s+".toRegex()) outputLogger.use {blog -> log.write("$i\t${tokens[1]}\t${tokens[3]}\t${tokens[5]}\n") }b }a

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for(i in 1..N) {a appendWriter.use {csources -> val javaclassfile = File(javaSourcesDir, "JavaTemp$i.java") javaclassfile.use {bout -> out.println("class JavaTemp$i {}") }b sources.write("$javaclassfile\n") }c val process = ProcessBuilder() .command("time", "javac", "@javasources/sources") .start() val timeOutput = process.errorStream.use(BufferedReader::readLine) val tokens = timeOutput.split("\\s+".toRegex()) outputLogger.use {blog -> log.write("$i\t${tokens[1]}\t${tokens[3]}\t${tokens[5]}\n") }b }a

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for(i in 1..N) {a appendWriter.use {csources -> val ktclassfile = File(ktSourcesDir, "KotlinTemp$i.kt") ktclassfile.use {bout -> out.println("class KotlinTemp$i {}") }b sources.write("$ktclassfile\n") }c val process = ProcessBuilder() .command("time", "kotlinc", "@ktsources/sources") .start() val timeOutput = process.errorStream.use(BufferedReader::readLine) val tokens = timeOutput.split("\\s+".toRegex()) outputLogger.use {blog -> log.write("$i\t${tokens[1]}\t${tokens[3]}\t${tokens[5]}\n") }b }a

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for (( i=1; i<="$N"; i++ )) do JAVACLASSFILE="$SOURCES/JavaTemp$i.java" echo "package app.cash.droidcon.to;" >> "$JAVACLASSFILE" echo "class JavaTemp$i {}" >> "$JAVACLASSFILE" TIMED=$(time (./gradlew java:assemble > /dev/null) 2>&1) DATA=$(echo -n "$TIMED" | cut -f2 -d'm' | cut -f1 -d's' | tr '\n' '\t') echo "$i$DATA" >> "$OUTPUT" done

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https://bit.ly/32DOCyf

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CardCustomizationData

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TouchData CardCustomizationData CardTheme

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TouchData Stroke StampCustomization CardCustomizationData CardTheme

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TouchData Stroke StampCustomization Point CardCustomizationData CardTheme

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:presenters :backend:api :app :backend:jvm https://git.io/JervG

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:presenters :backend:api :app :backend:jvm https://git.io/JervG kotlin-jvm com.android.library kotlin-android com.android.library kotlin-android kotlin-kapt com.android.application kotlin-android kotlin-kapt

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kapt?

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http://bit.ly/2CDcSWx

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:presenters :backend:api :app :backend:jvm

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kaptGenerateStubsDebugKotlin kaptDebugKotlin compileDebugKotlin

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kaptGenerateStubsDebugKotlin kaptDebugKotlin compileDebugKotlin

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class RealGreeter @Inject constructor() : Greeter { override fun greeting(name: String): Observable { return Observable .just(Greeting(message = "Hello $name!")) .delay(2, SECONDS) } } @kotlin.Metadata(…) public final class RealGreeter implements Greeter { @NotNull @Override public Observable greeting(@NotNull String name) { return null; } @Inject public RealGreeter() { super(); } } kaptGenerateStubsDebugKotlin

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class RealGreeter @Inject constructor() : Greeter { val publicField: Foo override fun greeting(name: String): Observable { … } } Application Binary Interface

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class RealGreeter @Inject constructor() : Greeter { val publicField: Foo override fun greeting(name: String): Observable { … } } Application Binary Interface

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kaptGenerateStubsDebugKotlin kaptDebugKotlin compileDebugKotlin

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kaptGenerateStubsDebugKotlin kaptDebugKotlin compileDebugKotlin

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@kotlin.Metadata(…) public final class RealGreeter implements Greeter { @NotNull @Override public Observable greeting(@NotNull String name) { return null; } @Inject public RealGreeter() { super(); } } kaptDebugKotlin public final class GreeterPresenter { @Inject Greeter greeter; public void present() {…} }

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kaptGenerateStubsDebugKotlin kaptDebugKotlin compileDebugKotlin

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kaptGenerateStubsDebugKotlin kaptDebugKotlin compileDebugKotlin

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kaptGenerateStubsDebugKotlin kaptDebugKotlin compileDebugKotlin

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Why are my builds slow?

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$ ./gradlew :app:assembleDebug BUILD SUCCESSFUL in 19s See the profiling report at: file:///Users/egor/.../cash/build/reports/ profile/profile-2019-11-11-11-33-51.html --profile

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$ echo kotlin.build.report.enable=true >> ~/.gradle/gradle.properties $ ./gradlew :app:assembleDebug $ echo kotlin.build.report.verbose=true >> ~/.gradle/gradle.properties Kotlin build report is written to /Users/egor/…/DCTO19CashApp/build/ reports/kotlin-build/DCTO19CashApp-build-2019-11-11-11-37-23.txt BUILD SUCCESSFUL in 19s

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Build cache Since Kotlin 1.2.21

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$ ./gradlew clean $ ./gradlew app:assembleDebug

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Incremental compilation Since Kotlin 1.1.1

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Incremental kapt Since Kotlin 1.3.30 Incremental compilation Since Kotlin 1.1.1

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$ ./gradlew :app:assembleDebug $ echo “class Test2” >> app/src/…/MainActivity.kt $ ./gradlew :app:assembleDebug

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Non-incremental compilation

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$ ./gradlew clean $ ./gradlew :app:assembleDebug $ echo “class Test3” >> app/src/…/MainActivity.kt $ ./gradlew :app:assembleDebug // FROM-CACHE

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http://bit.ly/34ZN5UQ

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https://github.com/JetBrains/kotlin/blob/master/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/ jetbrains/kotlin/gradle/tasks/Tasks.kt#L128

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Compilation avoidance

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If a dependency has changed in an ABI- compatible way (only its private API has changed), then Java compilation tasks will be up to-date. This means that if project A depends on project B and a class in B is changed in an ABI-compatible way (typically, changing only the body of a method), then Gradle won't recompile A.

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:app :presenters implementation // Add “private val a = 1” to presenters/ …/GreeterPresenter.kt $ ./gradlew :app:assembleDebug

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How do I debug my builds?

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kotlin.build.report.enable=true kotlin.build.report.verbose=true … $ ./gradlew :app:assembleDebug Kotlin build report is written to /Users/egor/…/DCTO19CashApp/build/ reports/kotlin-build/DCTO19CashApp-build-2019-11-11-11-37-23.txt BUILD SUCCESSFUL in 19s ~/.gradle/gradle.properties

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gradle.taskGraph.afterTask { task -> println " inputs: " task.inputs.files.each { println " " + it } println " outputs: " task.outputs.files.each { println " " + it } } ~/.gradle/gradle.properties

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> Task :app:kaptGenerateStubsDebugKotlin inputs: … outputs: …/app/build/tmp/kapt3/incrementalData/debug …/app/build/tmp/kapt3/stubs/debug > Task :app:kaptDebugKotlin inputs: … outputs: …/app/build/tmp/kapt3/classes/debug …/app/build/generated/source/kapt/debug …/app/build/generated/source/kaptKotlin/debug > Task :app:compileDebugKotlin inputs: … outputs: …/app/build/tmp/kotlin-classes/debug

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$ fswatch -xrt \ app/build/tmp/kapt3/incrementalData/debug \ app/build/tmp/kapt3/stubs/debug \ app/build/tmp/kapt3/classes/debug \ app/build/generated/source/kapt/debug \ app/build/generated/source/kaptKotlin/debug \ app/build/tmp/kotlin-classes/debug

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…/app/build/tmp/kotlin-classes/debug/…/cashapp/GreeterView.class Removed IsFile …/app/build/tmp/kotlin-classes/debug/…/cashapp Removed IsDir …/app/build/tmp/kotlin-classes/debug/…/cashapp Created IsDir …/app/build/tmp/kotlin-classes/debug/…/cashapp/GreeterView.class Created Updated IsFile