KTLN-651: Introduction to KotlinPoet (#896)

Author: sazzer

kotlin-libraries-2/pom.xml

@@ -132,6 +132,11 @@
             <artifactId>kotlinx-cli-jvm</artifactId>
             <version>0.3.5</version>
         </dependency>
+        <dependency>
+            <groupId>com.squareup</groupId>
+            <artifactId>kotlinpoet-jvm</artifactId>
+            <version>1.16.0</version>
+        </dependency>
     </dependencies>
     <build>
         <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>

kotlin-libraries-2/src/test/kotlin/com/baeldung/kotlin/kotlinpoet/FileUnitTest.kt

@@ -0,0 +1,33 @@
+package com.baeldung.kotlin.kotlinpoet
+
+import com.squareup.kotlinpoet.FileSpec
+import com.squareup.kotlinpoet.FunSpec
+import com.squareup.kotlinpoet.ParameterSpec
+import com.squareup.kotlinpoet.TypeSpec
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class FileUnitTest {
+    @Test
+    fun fullFile() {
+        val code = FileSpec.builder("com.baeldung.kotlin.kotlinpoet", "Testing.kt")
+            .addType(TypeSpec.classBuilder("Testing")
+                .addFunction(FunSpec.builder("count")
+                    .returns(Int::class)
+                    .addParameter(ParameterSpec.builder("items", List::class).build())
+                    .addStatement("return items.size()")
+                    .build())
+                .build())
+            .build()
+
+        assertEquals("""|package com.baeldung.kotlin.kotlinpoet
+            |
+            |import kotlin.Int
+            |import kotlin.collections.List
+            |
+            |public class Testing {
+            |  public fun count(items: List): Int = items.size()
+            |}
+            |""".trimMargin(), code.toString())
+    }
+}

kotlin-libraries-2/src/test/kotlin/com/baeldung/kotlin/kotlinpoet/FunctionUnitTest.kt

@@ -0,0 +1,110 @@
+package com.baeldung.kotlin.kotlinpoet
+
+import com.squareup.kotlinpoet.FunSpec
+import com.squareup.kotlinpoet.ParameterSpec
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class FunctionUnitTest {
+    @Test
+    fun emptyFunction() {
+        val code = FunSpec.builder("test")
+            .build()
+
+        assertEquals(
+            """|public fun test() {
+               |}
+               |""".trimMargin(),
+            code.toString())
+    }
+
+    @Test
+    fun simpleBody() {
+        val code = FunSpec.builder("test")
+            .addStatement("println(\"Testing\")")
+            .build()
+
+        assertEquals(
+            """|public fun test() {
+               |  println("Testing")
+               |}
+               |""".trimMargin(),
+            code.toString())
+    }
+
+    @Test
+    fun simpleBodyFormatSpecifier() {
+        val code = FunSpec.builder("test")
+            .addStatement("println(%S)", "Testing")
+            .build()
+
+        assertEquals(
+            """|public fun test() {
+               |  println("Testing")
+               |}
+               |""".trimMargin(),
+            code.toString())
+    }
+
+    @Test
+    fun controlFlow() {
+        val code = FunSpec.builder("test")
+            .beginControlFlow("if (showOutput)")
+            .addStatement("println(%S)", "Testing")
+            .nextControlFlow("else")
+            .addStatement("println()")
+            .endControlFlow()
+            .build()
+
+        assertEquals(
+            """|public fun test() {
+                |  if (showOutput) {
+                |    println("Testing")
+                |  } else {
+                |    println()
+                |  }
+                |}
+                |""".trimMargin(),
+            code.toString())
+    }
+
+    @Test
+    fun parameters() {
+        val code = FunSpec.builder("test")
+            .addParameter(ParameterSpec.builder("first", String::class).build())
+            .addParameter(ParameterSpec.builder("second", Int::class).defaultValue("%L", 42).build())
+            .build()
+
+        assertEquals(
+            """|public fun test(first: kotlin.String, second: kotlin.Int = 42) {
+               |}
+               |""".trimMargin(),
+            code.toString())
+    }
+
+    @Test
+    fun returns() {
+        val code = FunSpec.builder("test")
+            .returns(String::class)
+            .build()
+
+        assertEquals(
+            """|public fun test(): kotlin.String {
+               |}
+               |""".trimMargin(),
+            code.toString())
+    }
+
+    @Test
+    fun singleExpression() {
+        val code = FunSpec.builder("test")
+            .returns(Int::class)
+            .addStatement("return 5")
+            .build()
+
+        assertEquals(
+            """|public fun test(): kotlin.Int = 5
+               |""".trimMargin(),
+            code.toString())
+    }
+}

kotlin-libraries-2/src/test/kotlin/com/baeldung/kotlin/kotlinpoet/KotlinPoetUnitTest.kt

@@ -0,0 +1,18 @@
+package com.baeldung.kotlin.kotlinpoet
+
+import com.squareup.kotlinpoet.KModifier
+import com.squareup.kotlinpoet.TypeSpec
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class KotlinPoetUnitTest {
+    @Test
+    fun generateEmptyClass() {
+        val code = TypeSpec.classBuilder("Test")
+            .addModifiers(KModifier.PROTECTED)
+            .build()
+
+
+        assertEquals("protected class Test\n", code.toString())
+    }
+}

kotlin-libraries-2/src/test/kotlin/com/baeldung/kotlin/kotlinpoet/TypeUnitTest.kt

@@ -0,0 +1,52 @@
+package com.baeldung.kotlin.kotlinpoet
+
+import com.squareup.kotlinpoet.FunSpec
+import com.squareup.kotlinpoet.KModifier
+import com.squareup.kotlinpoet.PropertySpec
+import com.squareup.kotlinpoet.TypeSpec
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class TypeUnitTest {
+    @Test
+    fun emptyClass() {
+        val code = TypeSpec.classBuilder("Test")
+            .build()
+
+        assertEquals("""|public class Test
+            |""".trimMargin(), code.toString())
+    }
+
+    @Test
+    fun methods() {
+        val code = TypeSpec.classBuilder("Test")
+            .addFunction(FunSpec.builder("doSomething")
+                .returns(Int::class)
+                .addParameter("input", String::class)
+                .addModifiers(KModifier.PRIVATE)
+                .build())
+            .build()
+
+        assertEquals("""|public class Test {
+            |  private fun doSomething(input: kotlin.String): kotlin.Int {
+            |  }
+            |}
+            |""".trimMargin(), code.toString())
+    }
+
+    @Test
+    fun properties() {
+        val code = TypeSpec.classBuilder("Test")
+            .addProperty(PropertySpec.builder("test", String::class)
+                .addModifiers(KModifier.PRIVATE)
+                .mutable()
+                .initializer("%S", "Hello")
+                .build())
+            .build()
+
+        assertEquals("""|public class Test {
+            |  private var test: kotlin.String = "Hello"
+            |}
+            |""".trimMargin(), code.toString())
+    }
+}