Advanced techniques for building Kotlin DSL(s) - Android Worldwide

How to create Kotlin DSL that looks like the syntax of a programming language?
In this talk, I would like to talk about advanced techniques for creating Kotlin DSL.
As an example, we will see how to build a DSL that looks like a Starlark programming language, a Python dialect used for writing build scripts for Bazel build system. This DSL is a declarative code generator that builds an abstract syntax tree of a Starlark language and then generates a formatted code based on it.
However, all the concepts described in this talk are applicable to any kind of Kotlin DSL(s) including ones for Android projects.
The example project was presented at BazelCon 2021, a Google conference about Bazel build system: https://youtu.be/dz-CFEwJuko
In addition, there is a blog post that shows the capabilities of this DSL: https://proandroiddev.com/304fa8b3680c
The source code is available on GitHub: https://github.com/Morfly/airin

Transcript

2. About me • Google Developer Expert, Android • Mobile Infrastructure at Lyft 2
3. Agenda
4. • A concrete example of a Kotlin DSL Agenda 4
5. • A concrete example of a Kotlin DSL • DSL components Agenda 5
6. Concrete DSL example
7. Concrete DSL example • Starlark code generator (Python dialect) 7
8. Concrete DSL example • Starlark code generator (Python dialect) • Replicate Starlark syntax in Kotlin 8
9. Concrete DSL example • Starlark code generator (Python dialect) • Replicate Starlark syntax in Kotlin • https://github.com/Morfly/airin → airin-starlark 9
10. Concrete DSL example • Starlark code generator (Python dialect) • Replicate Starlark syntax in Kotlin • https://github.com/Morfly/airin → airin-starlark • BazelCon 2021: https://youtu.be/dz-CFEwJuko 10
11. Starlark code generator
12. // Starlark/Python SRC_FILES = ["MyClass.java"] android_binary( name = "app", srcs = ["MainActivity.java"] + SRCS_FILES, manifest = "AndroidManifest.xml", ) Starlark code generator 12
13. // Kotlin DSL val starlarkFile = BUILD.bazel { val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) } fileWriter.write(starlarkFile) // Creates BUILD.bazel file Starlark code generator 13
14. // Kotlin DSL val starlarkFile = BUILD.bazel { val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) } fileWriter.write(starlarkFile) // Creates BUILD.bazel file Starlark code generator 14
15. Starlark code generator android_binary function call Starlark file name argument srcs argument manifest argument + binary expression MainActivity.java string literal SRC_FILES reference app string literal AndroidManifest.xml string literal SRC_FILES … 15
16. // Kotlin DSL val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) Starlark code generator 16 android_binary function call Starlark file name argument srcs argument manifest argument + binary expression MainActivity.java string literal SRC_FILES reference app string literal AndroidManifest.xml string literal SRC_FILES …
17. // Kotlin DSL val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) Starlark code generator 17 android_binary function call Starlark file name argument srcs argument manifest argument + binary expression MainActivity.java string literal SRC_FILES reference app string literal AndroidManifest.xml string literal SRC_FILES … android_binary function call
18. // Kotlin DSL val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) Starlark code generator 18 android_binary function call Starlark file name argument srcs argument manifest argument + binary expression MainActivity.java string literal SRC_FILES reference app string literal AndroidManifest.xml string literal SRC_FILES … name argument app string literal
19. // Kotlin DSL val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) Starlark code generator 19 android_binary function call Starlark file name argument srcs argument manifest argument + binary expression MainActivity.java string literal SRC_FILES reference app string literal AndroidManifest.xml string literal SRC_FILES … manifest argument AndroidManifest.xml string literal
20. // Kotlin DSL val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) Starlark code generator 20 android_binary function call Starlark file name argument srcs argument manifest argument + binary expression MainActivity.java string literal SRC_FILES reference app string literal AndroidManifest.xml string literal SRC_FILES … srcs argument
21. // Kotlin DSL val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) Starlark code generator 21 android_binary function call Starlark file name argument srcs argument manifest argument + binary expression MainActivity.java string literal SRC_FILES reference app string literal AndroidManifest.xml string literal SRC_FILES … + binary expression
22. // Kotlin DSL val SRC_FILES by list["MyClass.java"] android_binary( name = "app", srcs = list["MainActivity.java"] `+` SRCS_FILES, manifest = "AndroidManifest.xml", ) Starlark code generator 22 android_binary function call Starlark file name argument srcs argument manifest argument + binary expression MainActivity.java string literal SRC_FILES reference app string literal AndroidManifest.xml string literal SRC_FILES … MainActivity.java string literal SRC_FILES reference
23. class StarlarkFile(val statements: List<Node>): Node Starlark code generator 23
24. class StarlarkFile(val statements: List<Node>): Node class FunctionCall(val name: String, val arguments: List<Node>): Node Starlark code generator 24
25. class StarlarkFile(val statements: List<Node>): Node class FunctionCall(val name: String, val arguments: List<Node>): Node class Argument(val name: String, param: Node) Starlark code generator 25
26. class StarlarkFile(val statements: List<Node>): Node class FunctionCall(val name: String, val arguments: List<Node>): Node class Argument(val name: String, param: Node) class StringLiteral(val value: String): Node class ListExpression(val items: List<Node>): Node class ListReference(val name: String): Node class BinaryPlus(val left: Node, val right: Node): Node Starlark code generator 26
27. Starlark DSL components
28. // Kotlin DSL val starlarkFile = BUILD.bazel { ... } fileWriter.write(starlarkFile) // Creates BUILD file Entering DSL context 28
29. // Kotlin DSL val starlarkFile = BUILD.bazel { ... } fileWriter.write(starlarkFile) // Creates BUILD file Entering DSL context 29
30. // Kotlin DSL val starlarkFile = BUILD.bazel { ... } fileWriter.write(starlarkFile) // Creates BUILD file Entering DSL context 30
31. // Implementation object BUILD inline fun BUILD.bazel(body: StarlarkFileContext.() -> Unit): StarlarkFile { val context = StarlarkFileContext() context.body() val nodes = context.nodes return StarlarkFile(path, nodes) } Lambdas with receiver 31
32. // Implementation object BUILD inline fun BUILD.bazel(body: StarlarkFileContext.() -> Unit): StarlarkFile { val context = StarlarkFileContext() context.body() val nodes = context.nodes return StarlarkFile(path, nodes) } Lambdas with receiver 32
33. // Implementation object BUILD inline fun BUILD.bazel(body: StarlarkFileContext.() -> Unit): StarlarkFile { val context = StarlarkFileContext() context.body() val nodes = context.nodes return StarlarkFile(path, nodes) } Lambdas with receiver 33
34. // Kotlin DSL val buildFile = BUILD.bazel { this: StarlarkFileContext -> android_binary( name = "app", srcs = list["MainActivity.java"], manifest = "AndroidManifest.xml", ) } Lambdas with receiver 34
35. // Kotlin DSL class StarlarkFileContext { fun android_binary(...) {...} } val buildFile = BUILD.bazel { this: StarlarkFileContext -> android_binary( name = "app", srcs = list["MainActivity.java"], manifest = "AndroidManifest.xml", ) } Lambdas with receiver 35
36. // Kotlin DSL class StarlarkFileContext { val statements = mutableListOf<Node>() fun android_binary(...) {...} } Lambdas with receiver 36
37. // Kotlin DSL class StarlarkFileContext { val statements = mutableListOf<Node>() fun android_binary(...) {...} } Lambdas with receiver 37
38. Functions
39. // Starlark/Python android_binary( name = "app", srcs = ["MainActivity.java"], manifest = "AndroidManifest.xml", ) Functions 39
40. // Starlark/Python android_binary( name = "app", srcs = ["MainActivity.java"], manifest = "AndroidManifest.xml", ) // Kotlin DSL android_binary( name = "app", srcs = list["MainActivity.java"], manifest = "AndroidManifest.xml", ) Functions 40
41. // Implementation fun StarlarkFileContext.android_binary( val name: String, val srcs: List<String?>? = null, val manifest: String? = null, ) { val args = listOf( Argument("name", StringLiteral(name)), Argument("srcs", ListExpression(srcs)), Argument("manifest", StringLiteral(manifest)) ) statements += FunctionCall("android_binary", args) } Functions 41
42. // Implementation fun StarlarkFileContext.android_binary( val name: String, val srcs: List<String?>? = null, val manifest: String? = null, ) { val args = listOf( Argument("name", StringLiteral(name)), Argument("srcs", ListExpression(srcs)), Argument("manifest", StringLiteral(manifest)) ) statements += FunctionCall("android_binary", args) } Functions 42
43. Indexed access operator
44. // Starlark/Python [1, 2, 3] Indexed access operator 44
45. // Starlark/Python [1, 2, 3] // Kotlin DSL list[1, 2, 3] Indexed access operator 45
46. // Implementation object _ListExpressionBuilder val list get() = _ListExpressionBuilder Indexed access operator 46
47. // Implementation object _ListExpressionBuilder val list get() = _ListExpressionBuilder operator fun <T> _ListExpressionBuilder.get(vararg args: T): List<T> { return ListExpression(listOf(*args)) } Indexed access operator 47
48. // Implementation object _ListExpressionBuilder val list get() = _ListExpressionBuilder operator fun <T> _ListExpressionBuilder.get(vararg args: T): List<T> { return ListExpression(listOf(*args)) } Indexed access operator 48
49. // Implementation object _ListExpressionBuilder val list get() = _ListExpressionBuilder operator fun <T> _ListExpressionBuilder.get(vararg args: T): List<T> { return ListExpression(listOf(*args)) } // Kotlin DSL list["MainActivity.java"] Indexed access operator 49
50. Property delegation
51. // Starlark/Python MY_STRING = "value" MY_LIST = [1, 2, 3] MY_DICT = {"key": "value"} Property delegation 51
52. // Starlark/Python MY_STRING = "value" MY_LIST = [1, 2, 3] MY_DICT = {"key": "value"} // Kotlin DSL val MY_STRING by "value" val MY_LIST by list[1, 2, 3] val MY_DICT by {"key" to "value"} Property delegation 52
53. // Starlark/Python MY_STRING = "value" MY_LIST = [1, 2, 3] MY_DICT = {"key": "value"} // Kotlin DSL val MY_STRING by "value" val MY_LIST by list[1, 2, 3] val MY_DICT by {"key" to "value"} Property delegation 53
54. // Starlark/Python MY_STRING = "value" MY_LIST = [1, 2, 3] MY_DICT = {"key": "value"} // Kotlin DSL val MY_STRING by "value" val MY_LIST by list[1, 2, 3] val MY_DICT by {"key" to "value"} Property delegation 54
55. // Starlark/Python MY_STRING = "value" MY_LIST = [1, 2, 3] MY_DICT = {"key": "value"} // Kotlin DSL val MY_STRING by "value" val MY_STRING = "value" val MY_LIST by list[1, 2, 3] val MY_DICT by {"key" to "value"} Property delegation 55
56. // Starlark/Python MY_STRING = "value" MY_LIST = [1, 2, 3] MY_DICT = {"key": "value"} // Kotlin DSL val MY_STRING: StringReference by "value" val MY_LIST: ListReference by list[1, 2, 3] val MY_DICT: DictionaryReference by {"key" to "value"} Property delegation 56
57. // Implementation class ListReference<out T>(val name: String) : List<T>, Node Property delegation 57
58. // Implementation class ListReference<out T>(val name: String) : List<T>, Node class DictionaryReference<K, V: Any>(val name: String) : Map<K, V>, Node Property delegation 58
59. // Implementation class ListReference<out T>(val name: String) : List<T>, Node class DictionaryReference<K, V: Any>(val name: String) : Map<K, V>, Node class StringReference(val name: String) : String, Node Property delegation 59
60. // Implementation class ListReference<out T>(val name: String) : List<T>, Node class DictionaryReference<K, V: Any>(val name: String) : Map<K, V>, Node class StringReference(val name: String) : CharSequence, Node Property delegation 60
61. // Kotlin DSL val NAME by "app" val SRCS by list["MainActivity.java"] val MANIFEST_VALUES by dict {"minSdkVersion" to "21"} android_binary( name = NAME, // String srcs = SRCS, // List manifest_values = MANIFEST_VALUES // Dictionary ) Property delegation 61
62. // Implementation fun StarlarkFileContext.android_binary( val name: CharSequence, val srcs: List<CharSequence?>? = null, val manifest_values: Map<CharSequence?, CharSequence?>? = null, ) {...} Property delegation 62
63. Making DSL customizable
64. Dynamic function args 64 // Starlark/Python android_binary( name = "app", srcs = ["MainActivity.java"], some_new_argument = {"key": "value"} )
65. Dynamic function args 65 // Starlark android_binary( name = "app", srcs = ["MainActivity.java"], some_new_argument = {"key": "value"} ) // Kotlin DSL android_binary { name = "app" srcs = list["MainActivity.java"] "some_new_argument" `=` {"key" to "value"} }
66. Dynamic function args 66 // Starlark android_binary( name = "app", srcs = ["MainActivity.java"], some_new_argument = {"key": "value"} ) // Kotlin DSL android_binary { name = "app" srcs = list["MainActivity.java"] "some_new_argument" `=` {"key" to "value"} }
67. Dynamic function args 67 // Starlark android_binary( name = "app", srcs = ["MainActivity.java"], some_new_argument = {"key": "value"} ) // Kotlin DSL android_binary { name = "app" srcs = list["MainActivity.java"] "some_new_argument" `=` {"key" to "value"} }
68. Dynamic function args 68 // Starlark android_binary( name = "app", srcs = ["MainActivity.java"], some_new_argument = {"key": "value"} ) // Kotlin DSL android_binary { this: AndroidBinaryContext -> name = "app" srcs = list["MainActivity.java"] "some_new_argument" `=` {"key" to "value"} }
69. Dynamic function args 69 // Implementation class AndroidBinaryContext { val args = linkedSetOf<Argument>() var name: CharSequence by args var srcs: ListType<CharSequence?>? by args var manifest: CharSequence? by args ... }
70. Dynamic function args 70 // Implementation class AndroidBinaryContext { val args = linkedSetOf<Argument>() var name: CharSequence by args var srcs: ListType<CharSequence?>? by args var manifest: CharSequence? by args ... operator fun <V : CharSequence?> Set<Argument>.setValue( thisRef: Any?, property: KProperty<*>, value: V ) { args += Argument(id = property.name, value = Expression(value, ::StringLiteral)) } }
71. Dynamic function args 71 // Implementation class AndroidBinaryContext { ... infix fun CharSequence.`=`(value: CharSequence) { args = Argument(id = this, value = Expression(value, ::StringLiteral)) } }
72. Dynamic function args 72 // Implementation class AndroidBinaryContext { ... infix fun CharSequence.`=`(value: CharSequence) { args = Argument(id = this, value = Expression(value, ::StringLiteral)) } } inline fun <T : Any> Expression(value: T?, builder: (value: T) -> Expression): Expression = when (value) { null -> NoneValue is Expression -> value else -> builder(value) }
73. Dynamic functions 73 // Starlark/Python some_new_function( name = "app", )
74. Dynamic functions 74 // Starlark/Python some_new_function( name = "app", ) // Kotlin DSL "some_new_function" { "name" `=` "app" }
75. Dynamic functions 75 // Implementation operator fun String.invoke(body: FunctionCallContext.() -> Unit) { val args = FunctionCallContext().apply(body).args statements += VoidFunctionCall(name, args) }
76. Dynamic functions 76 // Implementation operator fun String.invoke(body: FunctionCallContext.() -> Unit) { val args = FunctionCallContext().apply(body).args statements += VoidFunctionCall(name, args) }
77. Dynamic functions 77 // Implementation operator fun String.invoke(body: FunctionCallContext.() -> Unit) { val args = FunctionCallContext().apply(body).args statements += VoidFunctionCall(name, args) }
78. Combining elements
79. Concatenations 79 // Starlark/Python SOURCE_FILES = ["ProfileFragment.java", "ProfileViewModel.java"] android_binary( name = "app", srcs = SOURCE_FILES + ["MainActivity.java"], )
80. Concatenations 80 // Starlark/Python SOURCE_FILES = ["ProfileFragment.java", "ProfileViewModel.java"] android_binary( name = "app", srcs = SOURCE_FILES + ["MainActivity.java"], ) // Kotlin DSL val SOURCE_FILES by list["ProfileFragment.java", "ProfileViewModel.java"] android_binary( name = "app", srcs = SOURCE_FILES `+` list["MainActivity.java"], )
81. Concatenations 81 // Starlark/Python SOURCE_FILES = ["ProfileFragment.java", "ProfileViewModel.java"] android_binary( name = "app", srcs = SOURCE_FILES + ["MainActivity.java"], ) // Kotlin DSL val SOURCE_FILES by list["ProfileFragment.java", "ProfileViewModel.java"] android_binary( name = "app", srcs = SOURCE_FILES `+` list["MainActivity.java"], srcs = SOURCE_FILES + list["MainActivity.java"], )
82. Concatenations 82 // Implementation infix fun <T> List<T>?.`+`(other: List<T>?): List<T> = ListBinaryOperation( left = Expression(this, ::ListExpression), operator = BinaryOperator.PLUS, right = Expression(other, ::ListExpression) ) class ListBinaryOperation<T>( val left: Node, val operator: BinaryOperator, val right: Node ) : Node, List<T>
83. Concatenations 83 // Implementation infix fun <T> List<T>?.`+`(other: List<T>?): List<T> = ListBinaryOperation( left = Expression(this, ::ListExpression), operator = BinaryOperator.PLUS, right = Expression(other, ::ListExpression) ) class ListBinaryOperation<T>( val left: Node, val operator: BinaryOperator, val right: Node ) : Node, List<T>
84. Concatenations 84 // Implementation infix fun <T> List<T>?.`+`(other: List<T>?): List<T> = ListBinaryOperation( left = Expression(this, ::ListExpression), operator = BinaryOperator.PLUS, right = Expression(other, ::ListExpression) ) class ListBinaryOperation<T>( val left: Node, val operator: BinaryOperator, val right: Node ) : Node, List<T>
85. Concatenations 85 // Kotlin DSL val SOURCE_FILES by list["ProfileFragment.java", "ProfileViewModel.java"] android_binary { name = "app" srcs = SOURCE_FILES `+` list["MainActivity.java"] } android_binary { name = "app" "srcs" `=` SOURCE_FILES `+` list["MainActivity.java"] }
86. Concatenations 86 // Kotlin DSL val SOURCE_FILES by list["ProfileFragment.java", "ProfileViewModel.java"] android_binary { name = "app" srcs = SOURCE_FILES `+` list["MainActivity.java"] } android_binary { name = "app" "srcs" `=` SOURCE_FILES `+` list["MainActivity.java"] }
87. Concatenations 87 // Implementation infix fun String.`=`(value: CharSequence): _StringExpressionAccumulator<*> { val argument = Argument(id = this, value = Expression(value, ::StringLiteral)) args += argument return _StringExpressionAccumulator(argument) }
88. Concatenations 88 // Implementation infix fun String.`=`(value: CharSequence): _StringExpressionAccumulator<*> { val argument = Argument(id = this, value = Expression(value, ::StringLiteral)) args += argument return _StringExpressionAccumulator(argument) }
89. Concatenations 89 // Implementation infix fun <E : Node> _StringExpressionAccumulator<E>.`+`( other: CharSequence? ):_StringExpressionAccumulator<E> { this.arg.value = BinaryPlusOperator( left = this.arg.value, ..., right = other ) return this }
90. Concatenations 90 // Implementation infix fun <E : Node> _StringExpressionAccumulator<E>.`+`( other: CharSequence? ):_StringExpressionAccumulator<E> { this.arg.value = BinaryPlusOperator( left = this.arg.value, ..., right = other ) return this }
91. Context conflicts
92. Context conflicts 92 // Kotlin DSL BUILD.bazel { this: StarlarkFileContext -> android_binary { this: AndroidBinaryContext -> name = "app" srcs = list["MainActivity.java"] } }
93. Context conflicts 93 // Kotlin DSL BUILD.bazel { this: StarlarkFileContext -> android_binary { this: AndroidBinaryContext -> name = "app" srcs = list["MainActivity.java"] android_binary {...} } }
94. Context conflicts 94 // Kotlin DSL @DslMarker annotation class LanguageScope
95. Context conflicts 95 // Kotlin DSL @DslMarker annotation class LanguageScope @LanguageScope class StarlarkFileContext @LanguageScope class AndroidBinaryContext
96. Context conflicts 96 // Kotlin DSL BUILD.bazel { this: StarlarkFileContext -> android_binary { this: AndroidBinaryContext -> name = "app" srcs = list["MainActivity.java"] android_binary {...} } }
97. Context conflicts 97 // Kotlin DSL BUILD.bazel { this: StarlarkFileContext -> android_binary { this: AndroidBinaryContext -> name = "app" srcs = list["MainActivity.java"] `+` list["MainViewModel.java"] } }
98. Context conflicts 98 // Kotlin DSL BUILD.bazel { this: StarlarkFileContext -> android_binary { this: AndroidBinaryContext -> name = "app" srcs = list["MainActivity.java"] `+` list["MainViewModel.java"] } }
99. Restructuring the DSL
100. Restructuring the DSL 100 // Kotlin DSL sealed interface ConcatenationsFeature { // implement `+` operators }
101. Restructuring the DSL 101 // Kotlin DSL sealed interface ConcatenationsFeature { // implement `+` operators } @LanguageScope class StarlarkFileContext: ConcatenationsFeature {...} @LanguageScope class AndroidBinaryContext: ConcatenationsFeature {...}
102. Restructuring the DSL 102 // Kotlin DSL sealed interface ConcatenationsFeature { // implement `+` operators } @LanguageScope class StarlarkFileContext: ConcatenationsFeature {...} @LanguageScope class AndroidBinaryContext: ConcatenationsFeature {...}
103. Restructuring the DSL 103 // Kotlin DSL BUILD.bazel { this: StarlarkFileContext -> android_binary { this: AndroidBinaryContext -> name = "app" srcs = list["MainActivity.java"] `+` list["MainViewModel.java"] } }
104. Restructuring the DSL 104 // Kotlin DSL BUILD.bazel { this: StarlarkFileContext -> android_binary { this: AndroidBinaryContext -> name = "app" srcs = list["MainActivity.java"] `+` list["MainViewModel.java"] "manifest_values" `=` { this: DictionaryContext -> "key_" `+` "1" to "value_" `+` "1" } } }
105. Restructuring the DSL 105 // Kotlin DSL BUILD.bazel { android_binary { name = "app" "manifest_values" `=` { this: DictionaryContext -> "key_" `+` "1" to "value_" `+` "1" } } }
106. Additional features
107. List comprehensions 107 // Starlark/Python SRCS = [file + ".java" for file in ["MainActivity"]] android_binary( name = "app", srcs = SRCS )
108. List comprehensions 108 // Starlark/Python SRCS = [file + ".java" for file in ["MainActivity"]] android_binary( name = "app", srcs = SRCS ) // Kotlin DSL val SRCS by "file" `in` list["MainActivity"] take { it `+` ".java" } android_binary( name = "app", srcs = SRCS )
109. List comprehensions 109 // Starlark/Python SRCS = [file + ".java" for file in ["MainActivity"]] android_binary( name = "app", srcs = SRCS ) // Kotlin DSL val SRCS by "file" `in` list["MainActivity"] take { it `+` ".java" } android_binary( name = "app", srcs = SRCS )
110. List comprehensions 110 // Starlark/Python SRCS = [file + ".java" for file in ["MainActivity"]] android_binary( name = "app", srcs = SRCS ) // Kotlin DSL val SRCS by "file" `in` list["MainActivity"] take { it `+` ".java" } android_binary( name = "app", srcs = SRCS )
111. List comprehensions 111 // Starlark/Python SRCS = [file + ".java" for file in ["MainActivity"]] android_binary( name = "app", srcs = SRCS ) // Kotlin DSL val SRCS by "file" `in` list["MainActivity"] take { it `+` ".java" } android_binary( name = "app", srcs = SRCS )
112. List comprehensions 112 // Starlark/Python SRCS = [file + ".java" for file in ["MainActivity"]] android_binary( name = "app", srcs = SRCS ) // Kotlin DSL val SRCS by "file" `in` list["MainActivity"] take { it: CharSequence -> it `+` ".java" } android_binary( name = "app", srcs = SRCS )
113. List comprehensions 113 // Starlark/Python SRCS = [file + ".java" for file in ["MainActivity"]] android_binary( name = "app", srcs = SRCS ) // Kotlin DSL val SRCS by "file" `in` list["MainActivity"] take { it: CharSequence -> it `+` ".java" } android_binary( name = "app", srcs = SRCS )
114. Applying KSP
115. // Starlark/Python android_binary( name = "app", srcs = ["MainActivity.java"], manifest = "AndroidManifest.xml", ) Applying KSP 115
116. // Kotlin DSL class AndroidBinaryContext : FunctionCallContext() { var name: Name by fargs var custom_package: StringType? by fargs var manifest: Label? by fargs var manifest_values: DictionaryType<Key?, Value?>? by fargs var debug_key: Label? by fargs var enable_data_binding: BooleanType? by fargs var multidex: StringType? by fargs var incremental_dexing: NumberType? by fargs var crunch_png: BooleanType? by fargs var dex_shards: NumberType? by fargs var resource_files: ListType<Label?>? by fargs var srcs: ListType<Label?>? by fargs var plugins: ListType<Label?>? by fargs var deps: ListType<Label?>? by fargs var visibility: ListType<Label?>? by fargs var args: ListType<StringType?>? by fargs var env: DictionaryType<Key?, Value?>? by fargs var output_licenses: ListType<StringType?>? by fargs } fun BuildStatementsLibrary.`android_binary`(body: AndroidBinaryContext.() -> Unit): Unit = registerFunctionCallStatement("android_binary", AndroidBinaryContext(), body) Applying KSP 116
117. // Kotlin DSL class AndroidBinaryContext : FunctionCallContext() { var name: Name by fargs var custom_package: StringType? by fargs var manifest: Label? by fargs var manifest_values: DictionaryType<Key?, Value?>? by fargs var debug_key: Label? by fargs var enable_data_binding: BooleanType? by fargs var multidex: StringType? by fargs var incremental_dexing: NumberType? by fargs var crunch_png: BooleanType? by fargs var dex_shards: NumberType? by fargs var resource_files: ListType<Label?>? by fargs var srcs: ListType<Label?>? by fargs var plugins: ListType<Label?>? by fargs var deps: ListType<Label?>? by fargs var visibility: ListType<Label?>? by fargs var args: ListType<StringType?>? by fargs var env: DictionaryType<Key?, Value?>? by fargs var output_licenses: ListType<StringType?>? by fargs } fun BuildStatementsLibrary.`android_binary`(body: AndroidBinaryContext.() -> Unit): Unit = registerFunctionCallStatement("android_binary", AndroidBinaryContext(), body) Applying KSP 117 fun BuildStatementsLibrary.`android_binary`( name: Name, custom_package: StringType? = UnspecifiedString, manifest: Label? = UnspecifiedString, manifest_values: DictionaryType<Key?, Value?>? = UnspecifiedDictionary, debug_key: Label? = UnspecifiedString, enable_data_binding: BooleanType? = UnspecifiedBoolean, multidex: StringType? = UnspecifiedString, incremental_dexing: NumberType? = UnspecifiedNumber, crunch_png: BooleanType? = UnspecifiedBoolean, dex_shards: NumberType? = UnspecifiedNumber, resource_files: ListType<Label?>? = UnspecifiedList, srcs: ListType<Label?>? = UnspecifiedList, plugins: ListType<Label?>? = UnspecifiedList, deps: ListType<Label?>? = UnspecifiedList, visibility: ListType<Label?>? = UnspecifiedList, args: ListType<StringType?>? = UnspecifiedList, env: DictionaryType<Key?, Value?>? = UnspecifiedDictionary, output_licenses: ListType<StringType?>? = UnspecifiedList ): Unit { val _args = linkedSetOf<Argument>().also { it += Argument("name", Expression(name, ::StringLiteral)) if (custom_package !== UnspecifiedString) it += Argument("custom_package", Expression(custom_package, ::StringLiteral)) if (manifest !== UnspecifiedString) it += Argument("manifest", Expression(manifest, ::StringLiteral)) if (manifest_values !== UnspecifiedDictionary) it += Argument("manifest_values", Expression(manifest_values, ::DictionaryExpression)) if (debug_key !== UnspecifiedString) it += Argument("debug_key", Expression(debug_key, ::StringLiteral)) if (enable_data_binding !== UnspecifiedBoolean) it += Argument("enable_data_binding", Expression(enable_data_binding, ::BooleanLiteral)) if (multidex !== UnspecifiedString) it += Argument("multidex", Expression(multidex, ::StringLiteral)) if (incremental_dexing !== UnspecifiedNumber) it += Argument("incremental_dexing", Expression(incremental_dexing, ::NumberLiteral)) if (crunch_png !== UnspecifiedBoolean) it += Argument("crunch_png", Expression(crunch_png, ::BooleanLiteral)) if (dex_shards !== UnspecifiedNumber) it += Argument("dex_shards", Expression(dex_shards, ::NumberLiteral)) if (resource_files !== UnspecifiedList) it += Argument("resource_files", Expression(resource_files, ::ListExpression)) if (srcs !== UnspecifiedList) it += Argument("srcs", Expression(srcs, ::ListExpression)) if (plugins !== UnspecifiedList) it += Argument("plugins", Expression(plugins, ::ListExpression)) if (deps !== UnspecifiedList) it += Argument("deps", Expression(deps, ::ListExpression)) if (visibility !== UnspecifiedList) it += Argument("visibility", Expression(visibility, ::ListExpression)) if (args !== UnspecifiedList) it += Argument("args", Expression(args, ::ListExpression)) if (env !== UnspecifiedDictionary) it += Argument("env", Expression(env, ::DictionaryExpression)) if (output_licenses !== UnspecifiedList) it += Argument("output_licenses", Expression(output_licenses, ::ListExpression)) } return registerFunctionCallStatement("android_binary", _args) }
118. // Kotlin DSL @LibraryFunction(name = "android_binary",) private interface AndroidBinary { @Argument(required = true) val name: Name val manifest: CharSequence? val srcs: List<CharSequence?>? val deps: List<CharSequence?>? ... } Applying KSP 118
119. So, how do I write a Kotlin Symbol Processor (KSP)? https://proandroiddev.com/b9606e9e3818 Applying KSP 119
120. How does it look like in practice?
121. // Starlark/Python VIEW_MODELS_WITH_RES_IMPORTS = ["MyViewModel.kt", ...] [ genrule( name = "modify_imports_in_" + file[0:-3], srcs = [file], outs = [file[0:-3] + "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import org.morfly.airin.sample.app.R/import org.morfly.airin.sample.app.viewmodels.R/g' > $(OUTS) """, ) for file in VIEW_MODELS_WITH_RES_IMPORTS ] Usage example 121
122. // Starlark/Python VIEW_MODELS_WITH_RES_IMPORTS = ["MyViewModel.kt", ...] [ genrule( name = "modify_imports_in_" + file[0:-3], srcs = [file], outs = [file[0:-3] + "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import org.morfly.airin.sample.app.R/import org.morfly.airin.sample.app.viewmodels.R/g' > $(OUTS) """, ) for file in VIEW_MODELS_WITH_RES_IMPORTS ] Usage example 122
123. // Starlark/Python VIEW_MODELS_WITH_RES_IMPORTS = ["MyViewModel.kt", ...] [ genrule( name = "modify_imports_in_" + file[0:-3], srcs = [file], outs = [file[0:-3] + "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import org.morfly.airin.sample.app.R/import org.morfly.airin.sample.app.viewmodels.R/g' > $(OUTS) """, ) for file in VIEW_MODELS_WITH_RES_IMPORTS ] Usage example 123
124. // Starlark/Python VIEW_MODELS_WITH_RES_IMPORTS = ["MyViewModel.kt", ...] [ genrule( name = "modify_imports_in_" + file[0:-3], srcs = [file], outs = [file[0:-3] + "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import org.morfly.airin.sample.app.R/import org.morfly.airin.sample.app.viewmodels.R/g' > $(OUTS) """, ) for file in VIEW_MODELS_WITH_RES_IMPORTS ] Usage example 124
125. // Starlark/Python VIEW_MODELS_WITH_RES_IMPORTS = ["MyViewModel.kt", ...] [ genrule( name = "modify_imports_in_" + file[0:-3], srcs = [file], outs = [file[0:-3] + "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import org.morfly.airin.sample.app.R/import org.morfly.airin.sample.app.viewmodels.R/g' > $(OUTS) """, ) for file in VIEW_MODELS_WITH_RES_IMPORTS ] Usage example 125
126. // Starlark/Python VIEW_MODELS_WITH_RES_IMPORTS = ["MyViewModel.kt", ...] [ genrule( name = "modify_imports_in_" + file[0:-3], srcs = [file], outs = [file[0:-3] + "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import org.morfly.airin.sample.app.R/import org.morfly.airin.sample.app.viewmodels.R/g' > $(OUTS) """, ) for file in VIEW_MODELS_WITH_RES_IMPORTS ] Usage example 126
127. // Starlark/Python VIEW_MODELS_WITH_RES_IMPORTS = ["MyViewModel.kt", ...] [ genrule( name = "modify_imports_in_" + file[0:-3], srcs = [file], outs = [file[0:-3] + "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import org.morfly.airin.sample.app.R/import org.morfly.airin.sample.app.viewmodels.R/g' > $(OUTS) """, ) for file in VIEW_MODELS_WITH_RES_IMPORTS ] Usage example 127
128. val VIEW_MODELS_WITH_RES_IMPORTS by list["MyViewModel.kt", ...] "file" `in` VIEW_MODELS_WITH_RES_IMPORTS take { file -> genrule( name = "modify_imports_in_" `+` file[0..-3], srcs = list[file], outs = list[file[0..-3] `+` "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import $packageName.R/import $packageName.viewmodels.R/g' > $(OUTS) """.trimIndent() ) } Usage example 128
129. val VIEW_MODELS_WITH_RES_IMPORTS by list["MyViewModel.kt", ...] "file" `in` VIEW_MODELS_WITH_RES_IMPORTS take { file -> genrule( name = "modify_imports_in_" `+` file[0..-3], srcs = list[file], outs = list[file[0..-3] `+` "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import $packageName.R/import $packageName.viewmodels.R/g' > $(OUTS) """.trimIndent() ) } Usage example 129
130. val VIEW_MODELS_WITH_RES_IMPORTS by list["MyViewModel.kt", ...] "file" `in` VIEW_MODELS_WITH_RES_IMPORTS take { file -> genrule( name = "modify_imports_in_" `+` file[0..-3], srcs = list[file], outs = list[file[0..-3] `+` "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import $packageName.R/import $packageName.viewmodels.R/g' > $(OUTS) """.trimIndent() ) } Usage example 130
131. val VIEW_MODELS_WITH_RES_IMPORTS by list["MyViewModel.kt", ...] "file" `in` VIEW_MODELS_WITH_RES_IMPORTS take { file -> genrule( name = "modify_imports_in_" `+` file[0..-3], srcs = list[file], outs = list[file[0..-3] `+` "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import $packageName.R/import $packageName.viewmodels.R/g' > $(OUTS) """.trimIndent() ) } Usage example 131
132. val VIEW_MODELS_WITH_RES_IMPORTS by list["MyViewModel.kt", ...] "file" `in` VIEW_MODELS_WITH_RES_IMPORTS take { file -> genrule( name = "modify_imports_in_" `+` file[0..-3], srcs = list[file], outs = list[file[0..-3] `+` "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import $packageName.R/import $packageName.viewmodels.R/g' > $(OUTS) """.trimIndent() ) } Usage example 132
133. val VIEW_MODELS_WITH_RES_IMPORTS by list["MyViewModel.kt", ...] "file" `in` VIEW_MODELS_WITH_RES_IMPORTS take { file -> genrule( name = "modify_imports_in_" `+` file[0..-3], srcs = list[file], outs = list[file[0..-3] `+` "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import $packageName.R/import $packageName.viewmodels.R/g' > $(OUTS) """.trimIndent() ) } Usage example 133
134. val VIEW_MODELS_WITH_RES_IMPORTS by list["MyViewModel.kt", ...] "file" `in` VIEW_MODELS_WITH_RES_IMPORTS take { file -> genrule( name = "modify_imports_in_" `+` file[0..-3], srcs = list[file], outs = list[file[0..-3] `+` "_synthetic.kt"], cmd = """ cat $(SRCS) | sed 's/import $packageName.R/import $packageName.viewmodels.R/g' > $(OUTS) """.trimIndent() ) } Usage example 134
135. Conclusions
136. Conclusions 136 • Apply any type of Kotlin syntax elements for non-conventional cases
137. Conclusions 137 • Apply any type of Kotlin syntax elements for non-conventional cases • Experiment!
138. Source code 138 • https://github.com/Morfly/airin → airin-starlark