Annotation Processing in a Kotlin World

Annotation processing is a powerful tool to extend your codebase at build time, and the advent of Kotlin in the android community introduces a dimension to this. Kapt works with existing Java processors, but it doesn’t come without its quirks at the interop layer. This talk will dive into how you can leverage Kotlin bytecode’s @Metadata annotations to better understand Kotlin code during annotation processing, covering anywhere from case studies in Dagger and Moshi to leveraging tools like KotlinPoet to even generate Kotlin code that seamlessly leverages language features.

Transcript

1. Annotation Processing in a Kotlin World Zac Sweers @pandanomic
2. Annotation Processing in a Kotlin World
3. https://goo.gl/rSHTn4
5. Annotation Processing in a Kotlin World
6. Annotation Processing in a Kotlin World
7. Annotation Processing in a Kotlin World
8. Dagger @Inject @Qualifier
9. @Provides fun provideList(): List<Taco> { return emptyList() }a
10. @Provides fun provideList(): List<Taco> { return emptyList() }a @Inject lateinit var tacoList: List<Taco>
11. @Provides fun provideList(): List<Taco> { return emptyList() }a @Inject lateinit var tacoList: List<@SuppressJvmWildcard Taco>
12. @Provides fun provideList(): List<Taco> { return emptyList() }a @Inject lateinit var tacoList: List<@SuppressJvmWildcard Taco>
13. @Provides fun provideTaco(): Taco { return BreakfastTaco() }a @Inject lateinit var taco: Taco
14. @Breakfast @Provides fun provideTaco(): Taco { return BreakfastTaco() }a @Breakfast @Inject lateinit var taco: Taco
15. @Breakfast @Provides fun provideTaco(): Taco { return BreakfastTaco() }a @field:Breakfast @Inject lateinit var taco: Taco
16. @Breakfast @Provides fun provideTaco(): Taco { return BreakfastTaco() }a @field:Breakfast @Inject lateinit var taco: Taco
17. @Module class NetworkModule { @Provides static HttpClient provideHttpClient() { return HttpClient.create(); }a }b
18. @Module class NetworkModule { @Provides static HttpClient provideHttpClient() { return HttpClient.create(); }a companion object { }c }b
19. @Module class NetworkModule { companion object { @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b
20. @Module class NetworkModule { companion object { @JvmStatic @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b
21. @Module class NetworkModule { @Module companion object { @JvmStatic @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b
22. @Module class NetworkModule { @Module companion object { @JvmStatic @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b
23. @Module class NetworkModule { @Module companion object { @JvmStatic @Provides fun provideHttpClient(): HttpClient { return HttpClient.create() }a }c }b
24. Quick refresher
25. Quick refresher • Compile time
26. Quick refresher • Compile time • Since Java 5ish (APIs in Java 6)
27. Quick refresher • Compile time • Since Java 5ish (APIs in Java 6) • Reads Java (byte) code in intermediate format
28. Quick refresher • Compile time • Since Java 5ish (APIs in Java 6) • Reads Java (byte) code in intermediate format • Elements, Types, Filer, etc APIs
29. 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
30. 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
31. 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
32. 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
33. class Person(val name: String)
34. @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(); } }
35. 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(); } }
36. class Person(val name: String)
37. 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
38. 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
39. 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
40. class Person(val name: String = "Joe")
41. 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
42. 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
43. 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
44. class Person(val names: List<String>)
45. class Person(val names: List<String>) public Person(@NotNull List<String> names)
46. class Person(val names: MutableList<String>) public Person(@NotNull List<String> names)
47. 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(); } }
48. @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(); } }
49. @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(); } }
50. annotation class Metadata( )a
51. annotation class Metadata( val k: Int = 1 )a
52. annotation class Metadata( val k: Int = 1, val mv: IntArray = [] )a
53. annotation class Metadata( val k: Int = 1, val mv: IntArray = [], val bv: IntArray = [] )a
54. annotation class Metadata( val k: Int = 1, val mv: IntArray = [], val bv: IntArray = [], val d1: Array<String> = [] )a
55. annotation class Metadata( val k: Int = 1, val mv: IntArray = [], val bv: IntArray = [], val d1: Array<String> = [], val d2: Array<String> = [] )a
56. internal annotation class Metadata( val k: Int = 1, val mv: IntArray = [], val bv: IntArray = [], val d1: Array<String> = [], val d2: Array<String> = [] )a
57. @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(); } }
58. @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
59. @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
60. @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
61. @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
62. @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
63. @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
64. @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
65. @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
66. @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
67. @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
68. @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
73. val metadata = typeElement.getAnnotation(Metadata::class.java)
74. "Reading information from an annotation, you say?"
75. Compiler Plugins
76. Compiler Plugins • Faster/incremental
77. Compiler Plugins • Faster/incremental • No stubs generation
78. Compiler Plugins • Faster/incremental • No stubs generation • No kapt
79. Compiler Plugins • Faster/incremental • No stubs generation • No kapt
80. BUT!
81. BUT!
82. BUT! • Undocumented and not stable
83. BUT! • Undocumented and not stable • Only applies to Kotlin sources
84. BUT! • Undocumented and not stable • Only applies to Kotlin sources • Tooling can be painful
85. BUT! • Undocumented and not stable • Only applies to Kotlin sources • Tooling can be painful • github.com/hzsweers/redacted-compiler- plugin
86. 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
87. 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
88. "Reading information from an annotation, you say?"
89. kotlin-metadata https://github.com/takhion/kotlin-metadata
90. val metadata = typeElement.getAnnotation(Metadata::class.java)
91. val Element.kotlinMetadata: KotlinMetadata? val metadata = typeElement.getAnnotation(Metadata::class.java)
92. val Element.kotlinMetadata: KotlinMetadata? val metadata = typeElement.kotlinMetadata
93. when (typeElement.kotlinMetadata) { is KotlinPackageMetadata -> is KotlinClassMetadata -> is KotlinFileMetadata -> is KotlinMultiFileClassPartMetadata -> is KotlinMultiFileClassFacadeMetadata -> is KotlinSyntheticClassMetadata -> is KotlinUnknownMetadata -> }a
94. when (typeElement.kotlinMetadata) { is KotlinClassMetadata -> }a
95. when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data }a }b
96. when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data val proto: ProtoBuf.Class = classData.classProto }a }b
98. when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data val proto: ProtoBuf.Class = classData.classProto }a }b
99. when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data val proto: ProtoBuf.Class = classData.classProto val nameResolver = classData.nameResolver }a }b
100. @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
101. @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
102. @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
103. when (metadata) { is KotlinClassMetadata -> { val classData: ClassData = metadata.data val proto: ProtoBuf.Class = classData.classProto val nameResolver = classData.nameResolver }a }b
104. val proto: ProtoBuf.Class = classData.classProto val constructors: List<Constructor> = proto.constructorList val properties: List<Property> = proto.propertyList val functions: List<Function> = proto.functionList
105. class Person(val name: String = "Joe")
106. class Person(val name: String = "Joe") val name = TODO()
107. class Person(val name: String = "Joe") val name = TODO() val mutable = TODO()
108. class Person(val name: String = "Joe") val name = TODO() val mutable = TODO() val nullable = TODO()
109. class Person(val name: String = "Joe") val name = TODO() val mutable = TODO() val nullable = TODO() val hasDefault = TODO()
110. class Person(val name: String = "Joe") val name = TODO() val mutable = TODO() val nullable = TODO() val hasDefault = TODO()
111. 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()
112. it.isPrimary
113. val Constructor.isPrimary: Boolean get() { return !Flags.IS_SECONDARY[flags] }
114. 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()
115. 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()
116. 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()
117. 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
118. 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
119. 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
120. 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
121. kotlin-metadata
122. kotlinx-metadata
123. kotlinx-metadata https://github.com/JetBrains/kotlin/tree/master/libraries/kotlinx-metadata/jvm
124. kotlinx-metadata? https://github.com/JetBrains/kotlin/tree/master/libraries/kotlinx-metadata/jvm
125. kotlinx-metadata? https://github.com/JetBrains/kotlin/tree/master/libraries/kotlinx-metadata/jvm https://github.com/square/moshi/pull/642
126. Case Studies
127. copydynamic https://github.com/hzsweers/copydynamic
128. –Chris Banes, somewhere online once upon a time “I wish I could use copy but like, conditionally set properties”
129. data class Taco( val seasoning: Set<String>, val isBreakfast: Boolean )a
130. data class Taco( val seasoning: Set<String>, val isBreakfast: Boolean )a val taco = Taco(setOf("el paso"), true)
131. data class Taco( val seasoning: Set<String>, val isBreakfast: Boolean )a val taco = Taco(setOf("el paso"), true) val newTaco = taco.copyDynamic({ if (isBreakfastTime) { isBreakfast = true } }
132. class TacoDynamicBuilder constructor( private val source: Taco) { var seasoning: Set<String> = 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
133. class TacoDynamicBuilder constructor( private val source: Taco) { var seasoning: Set<String> = 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
134. class TacoDynamicBuilder constructor( private val source: Taco) { var seasoning: Set<String> = 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
135. data class Taco( val seasoning: Set<String>, val isBreakfast: Boolean )a
136. @CopyDynamic data class Taco( val seasoning: Set<String>, val isBreakfast: Boolean )aa
137. @CopyDynamic data class Taco( val seasoning: Set<String>, 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
138. @CopyDynamic data class Taco( val seasoning: Set<String>, 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
139. @CopyDynamic data class Taco( val seasoning: Set<String>, 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
140. @CopyDynamic data class Taco( val seasoning: Set<String>, 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
141. @CopyDynamic data class Taco( val seasoning: Set<String>, 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
142. @CopyDynamic data class Taco( val seasoning: Set<String>, 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
143. @CopyDynamic data class Taco( val seasoning: Set<String>, 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"
144. Moshi https://github.com/square/moshi API overview blog post: https://goo.gl/dRjqFb
145. Guidelines
146. Metadata is added signal
147. Abstract your renderer
148. Be mindful of mixed source sets
149. Lean on language features
150. Be mindful of quirks and caveats
151. Quirks & Caveats • Not public yet
152. Quirks & Caveats • Not public yet • Not incremental
153. Quirks & Caveats • Not public yet • Not incremental • No multiplatform
154. Quirks & Caveats • Not public yet • Not incremental • No multiplatform • (Kapt) No multiple rounds*
155. Quirks & Caveats • Not public yet • Not incremental • No multiplatform • (Kapt) No multiple rounds* • (Kapt) Varying build system support
156. Quirks & Caveats • Not public yet • Not incremental • No multiplatform • (Kapt) No multiple rounds* • (Kapt) Varying build system support
157. –you? “I have a processor and want to support kotlin today! What should I use?”
158. “I have a processor and want to support kotlin today! What should I use?” “kotlin-metadata, probably”
159. “I have a processor and want to support kotlin today! What should I use?” “kotlin-metadata, probably” “and KotlinPoet”
160. 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
161. Thanks! Special thanks to Eugenio Marletti (@workingkills)
162. Thanks! Zac Sweers @pandanomic