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Annotation Processing in a Kotlin World Zac Sweers @pandanomic

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Annotation Processing in a Kotlin World

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https://goo.gl/rSHTn4

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Annotation Processing in a Kotlin World

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Annotation Processing in a Kotlin World

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Annotation Processing in a Kotlin World

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Dagger @Inject @Qualifier

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@Provides fun provideList(): List { return emptyList() }a

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@Provides fun provideList(): List { return emptyList() }a @Inject lateinit var tacoList: List

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@Provides fun provideList(): List { return emptyList() }a @Inject lateinit var tacoList: List<@SuppressJvmWildcard Taco>

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@Provides fun provideList(): List { return emptyList() }a @Inject lateinit var tacoList: List<@SuppressJvmWildcard Taco>

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@Provides fun provideTaco(): Taco { return BreakfastTaco() }a @Inject lateinit var taco: Taco

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@Breakfast @Provides fun provideTaco(): Taco { return BreakfastTaco() }a @Breakfast @Inject lateinit var taco: Taco

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@Breakfast @Provides fun provideTaco(): Taco { return BreakfastTaco() }a @field:Breakfast @Inject lateinit var taco: Taco

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@Breakfast @Provides fun provideTaco(): Taco { return BreakfastTaco() }a @field:Breakfast @Inject lateinit var taco: Taco

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@Module class NetworkModule { @Provides static HttpClient provideHttpClient() { return HttpClient.create(); }a }b

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@Module class NetworkModule { @Provides static HttpClient provideHttpClient() { return HttpClient.create(); }a companion object { }c }b

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@Module class NetworkModule { companion object { @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b

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@Module class NetworkModule { companion object { @JvmStatic @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b

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@Module class NetworkModule { @Module companion object { @JvmStatic @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b

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@Module class NetworkModule { @Module companion object { @JvmStatic @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b

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@Module class NetworkModule { @Module companion object { @JvmStatic @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b

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Quick refresher

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Quick refresher • Compile time

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Quick refresher • Compile time • Since Java 5ish (APIs in Java 6)

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Quick refresher • Compile time • Since Java 5ish (APIs in Java 6) • Reads Java (byte) code in intermediate format

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Quick refresher • Compile time • Since Java 5ish (APIs in Java 6) • Reads Java (byte) code in intermediate format • Elements, Types, Filer, etc APIs

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Quick refresher • Compile time • Since Java 5ish (APIs in Java 6) • Reads Java (byte) code in intermediate format • Elements, Types, Filer, etc APIs • Cannot modify code, only generate more

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Quick refresher • Compile time • Since Java 5ish (APIs in Java 6) • Reads Java (byte) code in intermediate format • Elements, Types, Filer, etc APIs • Cannot modify code, only generate more • Multiple rounds

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Quick refresher • Compile time • Since Java 5ish (APIs in Java 6) • Reads Java (byte) code in intermediate format • Elements, Types, Filer, etc APIs • Cannot modify code, only generate more • Multiple rounds

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Quick refresher • Compile time • Since Java 5ish (APIs in Java 6) • Reads Java (byte) code in intermediate format • Elements, Types, Filer, etc APIs • Cannot modify code, only generate more • Multiple rounds

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class Person(val name: String)

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u00020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004\b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/String;)V", "getName", "()Ljava/lang/String;", "test- project"} ) public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; } public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); } }

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public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; } public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); } }

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class Person(val name: String)

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public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; }c public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); }a }b

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public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; }c public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); }a }b

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public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; }c public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); }a }b

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class Person(val name: String = "Joe")

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public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; }c public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); }a }b

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public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; }c public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); }a public Person() { super(); }d }b

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public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; }c public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); }a public Person() { super(); }d }b

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class Person(val names: List)

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class Person(val names: List) public Person(@NotNull List names)

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class Person(val names: MutableList) public Person(@NotNull List names)

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public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; } public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); } }

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u00020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004\b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; } public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); } }

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u00020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004\b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; } public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); } }

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annotation class Metadata( )a

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annotation class Metadata( val k: Int = 1 )a

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annotation class Metadata( val k: Int = 1, val mv: IntArray = [] )a

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annotation class Metadata( val k: Int = 1, val mv: IntArray = [], val bv: IntArray = [] )a

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annotation class Metadata( val k: Int = 1, val mv: IntArray = [], val bv: IntArray = [], val d1: Array = [] )a

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annotation class Metadata( val k: Int = 1, val mv: IntArray = [], val bv: IntArray = [], val d1: Array = [], val d2: Array = [] )a

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internal annotation class Metadata( val k: Int = 1, val mv: IntArray = [], val bv: IntArray = [], val d1: Array = [], val d2: Array = [] )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u00020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004\b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a public final class Person { @org.jetbrains.annotations.NotNull() private final java.lang.String name = null; @org.jetbrains.annotations.NotNull() public final java.lang.String getName() { return null; } public Person(@org.jetbrains.annotations.NotNull() java.lang.String name) { super(); } }

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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val metadata = typeElement.getAnnotation(Metadata::class.java)

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"Reading information from an annotation, you say?"

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Compiler Plugins

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Compiler Plugins • Faster/incremental

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Compiler Plugins • Faster/incremental • No stubs generation

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Compiler Plugins • Faster/incremental • No stubs generation • No kapt

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Compiler Plugins • Faster/incremental • No stubs generation • No kapt

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BUT!

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BUT!

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BUT! • Undocumented and not stable

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BUT! • Undocumented and not stable • Only applies to Kotlin sources

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BUT! • Undocumented and not stable • Only applies to Kotlin sources • Tooling can be painful

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BUT! • Undocumented and not stable • Only applies to Kotlin sources • Tooling can be painful • github.com/hzsweers/redacted-compiler- plugin

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BUT! • Undocumented and not stable • Only applies to Kotlin sources • Tooling can be painful • github.com/hzsweers/redacted-compiler- plugin • The talk title was Annotation Processing in a Kotlin

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BUT!* • Undocumented and not stable • Only applies to Kotlin sources • Tooling can be painful • github.com/hzsweers/redacted-compiler- plugin • The talk title was Annotation Processing in a Kotlin

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"Reading information from an annotation, you say?"

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kotlin-metadata https://github.com/takhion/kotlin-metadata

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val metadata = typeElement.getAnnotation(Metadata::class.java)

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val Element.kotlinMetadata: KotlinMetadata? val metadata = typeElement.getAnnotation(Metadata::class.java)

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val Element.kotlinMetadata: KotlinMetadata? val metadata = typeElement.kotlinMetadata

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when (typeElement.kotlinMetadata) { is KotlinPackageMetadata -> is KotlinClassMetadata -> is KotlinFileMetadata -> is KotlinMultiFileClassPartMetadata -> is KotlinMultiFileClassFacadeMetadata -> is KotlinSyntheticClassMetadata -> is KotlinUnknownMetadata -> }a

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when (typeElement.kotlinMetadata) { is KotlinClassMetadata -> }a

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when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data }a }b

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when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data val proto: ProtoBuf.Class = classData.classProto }a }b

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when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data val proto: ProtoBuf.Class = classData.classProto }a }b

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when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data val proto: ProtoBuf.Class = classData.classProto val nameResolver = classData.nameResolver }a }b

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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@kotlin.Metadata( mv = {1, 1, 11}, bv = {1, 0, 2}, k = 1, d1 = {"\u0000\u0012\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n \u0000\n\u0002\u0010\u000e\n\u0002\b\u0004\b\u0007\u0018 \u00002\u00020\u0001B\r\u0012\u0006\u0010\u0002\u001a\u0 0020\u0003\u00a2\u0006\u0002\u0010\u0004R\u0011\u0010\u0 002\u001a\u00020\u0003\u00a2\u0006\b\n\u0000\u001a\u0004 \b\u0005\u0010\u0006\u00a8\u0006\u0007"}, d2 = {"Ltest/Person;", "", "name", "", "(Ljava/lang/ String;)V", "getName", "()Ljava/lang/String;", "test- project"} )a

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when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data val proto: ProtoBuf.Class = classData.classProto val nameResolver = classData.nameResolver }a }b

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val proto: ProtoBuf.Class = classData.classProto val constructors: List = proto.constructorList val properties: List = proto.propertyList val functions: List = proto.functionList

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class Person(val name: String = "Joe")

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class Person(val name: String = "Joe") val name = TODO()

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class Person(val name: String = "Joe") val name = TODO() val mutable = TODO()

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class Person(val name: String = "Joe") val name = TODO() val mutable = TODO() val nullable = TODO()

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class Person(val name: String = "Joe") val name = TODO() val mutable = TODO() val nullable = TODO() val hasDefault = TODO()

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class Person(val name: String = "Joe") val name = TODO() val mutable = TODO() val nullable = TODO() val hasDefault = TODO()

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class Person(val name: String = "Joe") val proto = classData.classProto val constr = proto.constructorList.find { it.isPrimary } val name = TODO() val mutable = TODO() val nullable = TODO() val hasDefault = TODO()

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it.isPrimary

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val Constructor.isPrimary: Boolean get() { return !Flags.IS_SECONDARY[flags] }

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class Person(val name: String = "Joe") val proto = classData.classProto val constr = proto.constructorList.find { it.isPrimary } val name = TODO() val mutable = TODO() val nullable = TODO() val hasDefault = TODO()

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class Person(val name: String = "Joe") val proto = classData.classProto val constr = proto.constructorList.find { it.isPrimary } val nameParam = constr.valueParameterList[0] val name = TODO() val mutable = TODO() val nullable = TODO() val hasDefault = TODO()

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class Person(val name: String = "Joe") val proto = classData.classProto val constr = proto.constructorList.find { it.isPrimary } val nameParam = constr.valueParameterList[0] val name = nameResolver.getString(nameParam.name) val mutable = TODO() val nullable = TODO() val hasDefault = TODO()

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class Person(val name: String = "Joe") val proto = classData.classProto val constr = proto.constructorList.find { it.isPrimary } val nameParam = constr.valueParameterList[0] val name = nameResolver.getString(nameParam.name) val mutable = TODO() val nullable = TODO() val hasDefault = nameParam.declaresDefaultValue

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class Person(val name: String = "Joe") val proto = classData.classProto val constr = proto.constructorList.find { it.isPrimary } val nameParam = constr.valueParameterList[0] val name = nameResolver.getString(nameParam.name) val mutable = TODO() val nullable = nameParam.type.nullable val hasDefault = nameParam.declaresDefaultValue

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class Person(val name: String = "Joe") val proto = classData.classProto val constr = proto.constructorList.find { it.isPrimary } val nameParam = constr.valueParameterList[0] val name = nameResolver.getString(nameParam.name) val mutable = proto.propertyList[0].isVar val nullable = nameParam.type.nullable val hasDefault = nameParam.declaresDefaultValue

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class Person(val name: String = "Joe") val proto = classData.classProto val constr = proto.constructorList.find { it.isPrimary } val nameParam = constr.valueParameterList[0] val name = nameResolver.getString(nameParam.name) val mutable = proto.propertyList[0].isVar val nullable = nameParam.type.nullable val hasDefault = nameParam.declaresDefaultValue

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kotlin-metadata

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kotlinx-metadata

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kotlinx-metadata https://github.com/JetBrains/kotlin/tree/master/libraries/kotlinx-metadata/jvm

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kotlinx-metadata? https://github.com/JetBrains/kotlin/tree/master/libraries/kotlinx-metadata/jvm

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kotlinx-metadata? https://github.com/JetBrains/kotlin/tree/master/libraries/kotlinx-metadata/jvm https://github.com/square/moshi/pull/642

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Case Studies

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copydynamic https://github.com/hzsweers/copydynamic

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–Chris Banes, somewhere online once upon a time “I wish I could use copy but like, conditionally set properties”

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data class Taco( val seasoning: Set, val isBreakfast: Boolean )a

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data class Taco( val seasoning: Set, val isBreakfast: Boolean )a val taco = Taco(setOf("el paso"), true)

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data class Taco( val seasoning: Set, val isBreakfast: Boolean )a val taco = Taco(setOf("el paso"), true) val newTaco = taco.copyDynamic({ if (isBreakfastTime) { isBreakfast = true } }

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class TacoDynamicBuilder constructor( private val source: Taco) { var seasoning: Set = source.seasoning var isBreakfast: Boolean = source.isBreakfast fun build(): Taco = source.copy(seasoning, isBreakfast) }a fun Taco.copyDynamic( copyBlock: TacoDynamicBuilder.() -> Unit): Taco { return TacoDynamicBuilder(this) .also { copyBlock(it) } .build() }b

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class TacoDynamicBuilder constructor( private val source: Taco) { var seasoning: Set = source.seasoning var isBreakfast: Boolean = source.isBreakfast fun build(): Taco = source.copy(seasoning, isBreakfast) }a fun Taco.copyDynamic( copyBlock: TacoDynamicBuilder.() -> Unit): Taco { return TacoDynamicBuilder(this) .also { copyBlock(it) } .build() }b

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class TacoDynamicBuilder constructor( private val source: Taco) { var seasoning: Set = source.seasoning var isBreakfast: Boolean = source.isBreakfast fun build(): Taco = source.copy(seasoning, isBreakfast) }a fun Taco.copyDynamic( copyBlock: TacoDynamicBuilder.() -> Unit): Taco { return TacoDynamicBuilder(this) .also { copyBlock(it) } .build() }b

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data class Taco( val seasoning: Set, val isBreakfast: Boolean )a

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@CopyDynamic data class Taco( val seasoning: Set, val isBreakfast: Boolean )aa

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@CopyDynamic data class Taco( val seasoning: Set, val isBreakfast: Boolean )aa •Read the proto off Taco •Ensure it's a data class •Find constructor •Get all params + matching properties •Generate with KotlinPoet

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@CopyDynamic data class Taco( val seasoning: Set, val isBreakfast: Boolean )a •Read the proto off Taco •Ensure it's a data class •Find constructor •Get all params + matching properties •Generate with KotlinPoet

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@CopyDynamic data class Taco( val seasoning: Set, val isBreakfast: Boolean )a •Read the proto off Taco •Ensure it's a data class •Find constructor •Get all params + matching properties •Generate with KotlinPoet

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@CopyDynamic data class Taco( val seasoning: Set, val isBreakfast: Boolean )a •Read the proto off Taco •Ensure it's a data class •Find constructor •Get all params + matching properties •Generate with KotlinPoet

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@CopyDynamic data class Taco( val seasoning: Set, val isBreakfast: Boolean )a •Read the proto off Taco •Ensure it's a data class •Find constructor •Get all params + matching properties •Generate with KotlinPoet

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@CopyDynamic data class Taco( val seasoning: Set, val isBreakfast: Boolean )a •Read the proto off Taco •Ensure it's a data class •Find constructor •Get all params + matching properties •Generate with KotlinPoet

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@CopyDynamic data class Taco( val seasoning: Set, val isBreakfast: Boolean )a •Read the proto off Taco •Ensure it's a data class •Find constructor •Get all params + matching properties •Generate with KotlinPoet "kapt.kotlin.generated"

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Moshi https://github.com/square/moshi API overview blog post: https://goo.gl/dRjqFb

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Guidelines

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Metadata is added signal

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Abstract your renderer

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Be mindful of mixed source sets

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Lean on language features

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Be mindful of quirks and caveats

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Quirks & Caveats • Not public yet

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Quirks & Caveats • Not public yet • Not incremental

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Quirks & Caveats • Not public yet • Not incremental • No multiplatform

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Quirks & Caveats • Not public yet • Not incremental • No multiplatform • (Kapt) No multiple rounds*

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Quirks & Caveats • Not public yet • Not incremental • No multiplatform • (Kapt) No multiple rounds* • (Kapt) Varying build system support

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Quirks & Caveats • Not public yet • Not incremental • No multiplatform • (Kapt) No multiple rounds* • (Kapt) Varying build system support

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–you? “I have a processor and want to support kotlin today! What should I use?”

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“I have a processor and want to support kotlin today! What should I use?” “kotlin-metadata, probably”

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“I have a processor and want to support kotlin today! What should I use?” “kotlin-metadata, probably” “and KotlinPoet”

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Thanks! • kotlin-metadata: github.com/takhion/kotlin-metadata • kotlinx-metadata: https://github.com/JetBrains/kotlin/tree/master/ libraries/kotlinx-metadata/jvm • Moshi: github.com/square/moshi • Km API prototype: github.com/square/moshi/pull/642 • CopyDynamic: github.com/hzsweers/copydynamic • FR for value type API: youtrack.jetbrains.com/issue/KT-26602 • Multiple rounds demo: github.com/Takhion/generate-kotlin-multiple-rounds • redacted compiler plugin: github.com/hzsweers/redacted-compiler-plugin • KotlinPoet: github.com/square/kotlinpoet

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Thanks! Special thanks to Eugenio Marletti (@workingkills)

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Thanks! Zac Sweers @pandanomic