### Filter Diagnostic Messages by Severity

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Access and filter compilation diagnostic messages by severity level. Use `messagesWithSeverity` to get specific error, warning, or info messages.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import com.tschuchort.compiletesting.DiagnosticSeverity
import com.tschuchort.compiletesting.DiagnosticMessage
import org.assertj.core.api.Assertions.assertThat

val result = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("Warnings.kt", """
            @Deprecated("Use newMethod instead")
            fun oldMethod() {}

            fun caller() {
                oldMethod()  // Should produce deprecation warning
            }
        """)
    )
    verbose = true
}.compile()

// Access all diagnostic messages with severity info
val diagnostics: List<DiagnosticMessage> = result.diagnosticMessages
diagnostics.forEach { msg ->
    println("${msg.severity}: ${msg.message}")
}

// Filter messages by severity
val errors = result.messagesWithSeverity(DiagnosticSeverity.ERROR)
val warnings = result.messagesWithSeverity(DiagnosticSeverity.WARNING)
val infos = result.messagesWithSeverity(DiagnosticSeverity.INFO)

// Check for specific diagnostic
assertThat(result.diagnosticMessages).anyMatch {
    it.severity == DiagnosticSeverity.WARNING &&
    it.message.contains("Deprecated")
}

// Multiple severity levels
val errorsAndWarnings = result.messagesWithSeverity(
    DiagnosticSeverity.ERROR,
    DiagnosticSeverity.WARNING
)
```

--------------------------------

### Create Arbitrary Source File

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Use `SourceFile.new` to create source files with any extension. This is useful for including arbitrary files in the compilation working directory, such as configuration files or scripts.

```kotlin
import com.tschuchort.compiletesting.SourceFile

// Create a generic source file
val customSource = SourceFile.new(
    "config.properties",
    """
    app.name=MyApplication
    app.version=1.0.0
    """)

// Create Kotlin script file
val scriptSource = SourceFile.new(
    "build.gradle.kts",
    """
    plugins {
        kotlin("jvm") version "2.0.0"
    }
    """)
```

--------------------------------

### Create Source Files for Compilation

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/README.md

Define Kotlin and Java source files using SourceFile factory methods for use in compilation tests.

```Kotlin
class TestEnvClass {}

@Test
fun `test my annotation processor`() {
  val kotlinSource = SourceFile.kotlin(
    "KClass.kt", """
        class KClass {
            fun foo() {
                // Classes from the test environment are visible to the compiled sources
                val testEnvClass = TestEnvClass()
            }
        }
    """
  )

  val javaSource = SourceFile.java(
    "JClass.java", """
        public class JClass {
            public void bar() {
                // compiled Kotlin classes are visible to Java sources
                KClass kClass = new KClass();
            }
      }
    """
  )
}
```

--------------------------------

### Create Java Source File

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Use `SourceFile.java` to create Java source files for compilation. The file name must end with `.java`. Automatic indent trimming is enabled by default but can be disabled.

```kotlin
import com.tschuchort.compiletesting.SourceFile

// Create a simple Java source file
val javaSource = SourceFile.java(
    "MyService.java",
    """
    package com.example;

    public class MyService {
        public String process(String input) {
            return input.toUpperCase();
        }
    }
    """)

// Create Java interface
val interfaceSource = SourceFile.java(
    "Repository.java",
    """
    package com.example;

    public interface Repository<T> {
        T findById(long id);
        void save(T entity);
    }
    """)
```

--------------------------------

### Configure KSP Options

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Fine-tune KSP behavior with options for incremental processing, logging levels, and custom processor arguments. Use `configureKsp` for detailed settings or direct properties for simpler configurations.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import com.tschuchort.compiletesting.configureKsp
import com.tschuchort.compiletesting.kspIncremental
import com.tschuchort.compiletesting.kspAllWarningsAsErrors
import com.tschuchort.compiletesting.kspProcessorOptions
import com.tschuchort.compiletesting.kspLoggingLevels
import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity
import java.util.EnumSet

val compilation = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("Example.kt", """
            @com.example.Generated
            class Example
        """)
    )
    inheritClassPath = true

    configureKsp {
        // Add processor providers
        symbolProcessorProviders += MyProcessorProvider()

        // Incremental processing
        incremental = true
        incrementalLog = true

        // Error handling
        allWarningsAsErrors = true

        // Custom processor options (passed to your processors)
        processorOptions["generateBuilders"] = "true"
        processorOptions["outputPackage"] = "com.example.generated"

        // Control logging verbosity
        loggingLevels = EnumSet.of(
            CompilerMessageSeverity.ERROR,
            CompilerMessageSeverity.WARNING,
            CompilerMessageSeverity.INFO
        )
    }
}

// Alternative property-based configuration
val compilation2 = KotlinCompilation().apply {
    sources = listOf(/* ... */)
    inheritClassPath = true
    kspIncremental = true
    kspAllWarningsAsErrors = false
    kspProcessorOptions = mutableMapOf(
        "debug" to "true",
        "flavor" to "production"
    )
}
```

--------------------------------

### Dependency Versions

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/CHANGELOG.md

List of library dependencies for version 0.2.0.

```text
Kotlin (and its associated artifacts) 1.8.0
KSP 1.8.0
Classgraph: 4.8.153
```

--------------------------------

### Configure KSP Processors for Compilation

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Use `configureKsp` to add KSP processor providers. Ensure KSP is correctly set up to process annotations and generate code.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import com.tschuchort.compiletesting.symbolProcessorProviders
import com.tschuchort.compiletesting.kspSourcesDir
import com.tschuchort.compiletesting.configureKsp
import com.google.devtools.ksp.processing.*
import com.google.devtools.ksp.symbol.*
import org.assertj.core.api.Assertions.assertThat

// Define a KSP processor provider
class GeneratorProcessorProvider : SymbolProcessorProvider {
    override fun create(environment: SymbolProcessorEnvironment): SymbolProcessor {
        return GeneratorProcessor(environment.codeGenerator, environment.logger)
    }
}

class GeneratorProcessor(
    private val codeGenerator: CodeGenerator,
    private val logger: KSPLogger
) : SymbolProcessor {
    override fun process(resolver: Resolver): List<KSAnnotated> {
        resolver.getSymbolsWithAnnotation("com.example.Generate")
            .filterIsInstance<KSClassDeclaration>()
            .forEach {
                val packageName = it.packageName.asString()
                val className = "${it.simpleName.asString()}Impl"

                codeGenerator.createNewFile(
                    Dependencies(false, it.containingFile!!),
                    packageName,
                    className
                ).bufferedWriter().use {
                    it.write("""
                        package $packageName

                        class $className : ${it.simpleName.asString()} {
                            override fun execute() = "Generated implementation"
                        }
                    """.trimIndent())
                }

                logger.info("Generated $className")
            }
        return emptyList()
    }
}

// Compile with KSP
val compilation = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("Generate.kt", """
            package com.example
            annotation class Generate
        """,
        SourceFile.kotlin("Service.kt", """
            package com.example
            @Generate
            interface Service {
                fun execute(): String
            }
        """)
    )
    inheritClassPath = true
    configureKsp {
        symbolProcessorProviders += GeneratorProcessorProvider()
    }
}

val result = compilation.compile()

assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)

// Check KSP generated sources directory
val generatedFiles = compilation.kspSourcesDir.walkTopDown()
    .filter { it.isFile }
    .toList()
assertThat(generatedFiles.map { it.name }).contains("ServiceImpl.kt")

// Load and use generated class
val implClass = result.classLoader.loadClass("com.example.ServiceImpl")
val instance = implClass.getDeclaredConstructor().newInstance()
val method = implClass.getMethod("execute")
assertThat(method.invoke(instance)).isEqualTo("Generated implementation")

```

--------------------------------

### Configure Kotlin Compilation Options

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Set language version, JVM target, classpath, and output streams for Kotlin compilation. Inherit classpaths from the test environment for convenience.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import java.io.ByteArrayOutputStream
import java.io.File

val outputStream = ByteArrayOutputStream()

val result = KotlinCompilation().apply {
    // Source files
    sources = listOf(
        SourceFile.kotlin("Main.kt", """
            package app
            fun main() { println("Hello") }
        """)
    )

    // Kotlin/JVM settings
    languageVersion = "2.0"
    apiVersion = "2.0"
    jvmTarget = "17"

    // Classpath configuration
    inheritClassPath = true  // Inherit test classpath
    classpaths = listOf(File("libs/dependency.jar"))  // Additional jars

    // JDK configuration
    jdkHome = File(System.getProperty("java.home"))

    // Output and diagnostics
    verbose = true
    messageOutputStream = outputStream
    allWarningsAsErrors = false
    suppressWarnings = false

    // Module settings
    moduleName = "my-module"

    // Javac arguments for Java compilation step
    javacArguments = mutableListOf("-Xlint:all")

    // Additional kotlinc CLI arguments
    kotlincArguments = listOf("-Xjsr305=strict")

    // Opt-in annotations
    optIn = listOf("kotlin.RequiresOptIn", "kotlinx.coroutines.ExperimentalCoroutinesApi")
}.compile()

// Check compilation messages
val messages = outputStream.toString("UTF-8")
println("Compilation output: $messages")
```

--------------------------------

### Configure JVM Arguments for Java 16+ Compatibility (Gradle)

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/README.md

Add these JVM arguments to your test task in build.gradle to resolve Java 16+ access control issues with KAPT.

```Groovy
if (JavaVersion.current() >= JavaVersion.VERSION_16) {
    test {
        jvmArgs(
          "--add-opens=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.jvm=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED",
          "--add-opens=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED")
    }
}
```

--------------------------------

### Create Kotlin Source File

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Use `SourceFile.kotlin` to create Kotlin source files for compilation. The file name must end with `.kt`. Automatic indent trimming is enabled by default but can be disabled.

```kotlin
import com.tschuchort.compiletesting.SourceFile

// Create a simple Kotlin source file
val kotlinSource = SourceFile.kotlin(
    "MyClass.kt",
    """
    package com.example

    class MyClass {
        fun greet(): String = "Hello, World!"
    }
    """)

// Create Kotlin source with package structure in path
val packagedSource = SourceFile.kotlin(
    "com/example/domain/User.kt",
    """
    package com.example.domain

    data class User(val id: Long, val name: String)
    """)

// Disable automatic indent trimming
val rawSource = SourceFile.kotlin(
    "Formatted.kt",
    "class Formatted {}",
    trimIndent = false
)
```

--------------------------------

### Configure Compilation Parameters

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/README.md

Use KotlinCompilation to set source files, annotation processors, compiler plugins, and classpath inheritance.

```Kotlin
    val result = KotlinCompilation().apply {
        sources = listOf(kotlinSource, javaSource)

        // pass your own instance of an annotation processor
        annotationProcessors = listOf(MyAnnotationProcessor())

        // pass your own instance of a compiler plugin
        compilerPlugins = listOf(MyComponentRegistrar())
  commandLineProcessors = listOf(MyCommandlineProcessor())

        inheritClassPath = true
        messageOutputStream = System.out // see diagnostics in real time
    }.compile()
```

--------------------------------

### Compile Kotlin and Java Sources

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

The `KotlinCompilation` class is the main entry point for compiling sources. Configure `sources`, `inheritClassPath`, and other options before calling `compile()`. The result contains the exit code, messages, and compiled classes.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import org.assertj.core.api.Assertions.assertThat

// Basic compilation
val result = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("Example.kt", """
            class Example {
                fun compute(): Int = 42
            }
        """)
    )
}.compile()

assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)

// Compile mixed Kotlin and Java sources
val mixedResult = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("KotlinClass.kt", """
            package com.example
            class KotlinClass {
                fun process() = JavaHelper.help()
            }
        """),
        SourceFile.java("JavaHelper.java", """
            package com.example;
            public class JavaHelper {
                public static String help() { return "helped"; }
            }
        """ )
    )
    inheritClassPath = true
}.compile()

assertThat(mixedResult.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)
```

--------------------------------

### Configure Annotation Processing with KAPT

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Shows how to define a custom annotation processor and register it within the KotlinCompilation configuration.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import javax.annotation.processing.AbstractProcessor
import javax.annotation.processing.RoundEnvironment
import javax.lang.model.element.TypeElement
import javax.tools.Diagnostic
import org.assertj.core.api.Assertions.assertThat

// Define a simple annotation processor
class LoggingProcessor : AbstractProcessor() {
    override fun getSupportedAnnotationTypes() = setOf("com.example.Logged")

    override fun process(
        annotations: MutableSet<out TypeElement>,
        roundEnv: RoundEnvironment
    ): Boolean {
        for (element in roundEnv.getElementsAnnotatedWith(
            processingEnv.elementUtils.getTypeElement("com.example.Logged")
        )) {
            processingEnv.messager.printMessage(
                Diagnostic.Kind.NOTE,
                "Processing: ${element.simpleName}"
            )
        }
        return false
    }
}

// Compile with annotation processor
val result = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("Logged.kt", """
            package com.example
            annotation class Logged
        """),
        SourceFile.kotlin("Service.kt", """
            package com.example
            @Logged
            class UserService {
                fun getUser(id: Long) = "User-${'$'}id"
            }
        """)
    )
    annotationProcessors = listOf(LoggingProcessor())
    inheritClassPath = true
}.compile()

assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)
assertThat(result.messages).contains("Processing: UserService")

// Access generated sources
val generatedSources = result.sourcesGeneratedByAnnotationProcessor
```

--------------------------------

### Add Dependency to Build Gradle

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/README.md

Include the library in your project by adding the dependency to your build.gradle file.

```Groovy
dependencies {
        // ...
  testImplementation("dev.zacsweers.kctfork:core:<version>>")
}
```

--------------------------------

### Configure JVM Arguments for Java 16+ Compatibility (Kotlin DSL)

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/README.md

Use this Kotlin DSL configuration to add necessary JVM arguments for Java 16+ compatibility in your test tasks.

```Kotlin
if (JavaVersion.current() >= JavaVersion.VERSION_16) {
    tasks.withType<Test>().configureEach {
        jvmArgs(
            "--add-opens=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.jvm=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED",
            "--add-opens=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED")
    }
}
```

--------------------------------

### Migrate Component Registrars

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/CHANGELOG.md

Update from the deprecated compilerPlugins property to componentRegistrars.

```diff
KotlinCompilation().apply {
-  compilerPlugins = listOf(MyComponentRegistrar())
+  componentRegistrars = listOf(MyComponentRegistrar())
}
```

--------------------------------

### Access JvmCompilationResult properties

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Demonstrates how to inspect compilation exit codes, compiler messages, and load generated classes using the classLoader.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import org.assertj.core.api.Assertions.assertThat

val source = SourceFile.kotlin("Calculator.kt", """
    package math

    class Calculator {
        fun add(a: Int, b: Int): Int = a + b
        fun multiply(a: Int, b: Int): Int = a * b
    }
""")

val result = KotlinCompilation().apply {
    sources = listOf(source)
    inheritClassPath = true
}.compile()

// Check exit code
assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)

// Access compiler messages
println(result.messages)

// Load compiled class via classLoader
val calculatorClass = result.classLoader.loadClass("math.Calculator")
val instance = calculatorClass.getDeclaredConstructor().newInstance()

// Invoke methods via reflection
val addMethod = calculatorClass.getMethod("add", Int::class.java, Int::class.java)
val sum = addMethod.invoke(instance, 5, 3)
assertThat(sum).isEqualTo(8)

// Check generated files
assertThat(result.compiledClassAndResourceFiles.map { it.name })
    .contains("Calculator.class")

// Access output directory
val outputDir = result.outputDirectory
assertThat(outputDir.resolve("math/Calculator.class")).exists()
```

--------------------------------

### Multi-Step Compilation with addPreviousResultToClasspath

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Chain multiple compilations where the output of one is used as input for the next. This is useful for testing code that depends on previously compiled artifacts. Ensure `inheritClassPath` is true for both compilations.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import com.tschuchort.compiletesting.addPreviousResultToClasspath
import org.assertj.core.api.Assertions.assertThat

// Step 1: Compile base interface
val baseResult = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("Base.kt", """
            package base

            interface Repository<T> {
                fun findById(id: Long): T?
                fun save(entity: T)
            }
        """)
    )
    inheritClassPath = true
}.compile()

assertThat(baseResult.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)

// Step 2: Compile implementation that depends on base
val implResult = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("UserRepository.kt", """
            package impl

            import base.Repository

            data class User(val id: Long, val name: String)

            class UserRepository : Repository<User> {
                private val storage = mutableMapOf<Long, User>()

                override fun findById(id: Long): User? = storage[id]
                override fun save(entity: User) { storage[entity.id] = entity }
            }
        """)
    )
    inheritClassPath = true
}
    .addPreviousResultToClasspath(baseResult)  // Add base compilation output
    .compile()

assertThat(implResult.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)

// Load and test the implementation
val repoClass = implResult.classLoader.loadClass("impl.UserRepository")
val userClass = implResult.classLoader.loadClass("impl.User")

```

--------------------------------

### Configure Kotlin Compilation with KSP Processors

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/README.md

Use this Kotlin code to set up a compilation task with custom KSP symbol processor providers.

```Kotlin
class MySymbolProcessorProvider : SymbolProcessorProvider {
    // implementation of the SymbolProcessorProvider from the KSP API
}
val compilation = KotlinCompilation().apply {
    sources = listOf(source)
    symbolProcessorProviders = listOf(MySymbolProcessorProvider())
}
val result = compilation.compile()
```

--------------------------------

### Register Custom Compiler Plugins

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Register custom compiler plugins and command line processors using `compilerPluginRegistrars` and `commandLineProcessors`. This allows modification of compilation behavior or addition of custom phases.

```kotlin
import com.tschuchort.compiletesting.KotlinCompilation
import com.tschuchort.compiletesting.SourceFile
import com.tschuchort.compiletesting.PluginOption
import org.jetbrains.kotlin.compiler.plugin.CommandLineProcessor
import org.jetbrains.kotlin.compiler.plugin.CompilerPluginRegistrar
import org.jetbrains.kotlin.compiler.plugin.ExperimentalCompilerApi
import org.jetbrains.kotlin.compiler.plugin.CliOption
import org.jetbrains.kotlin.config.CompilerConfiguration
import org.assertj.core.api.Assertions.assertThat

@OptIn(ExperimentalCompilerApi::class)
class MyCommandLineProcessor : CommandLineProcessor {
    override val pluginId = "com.example.myplugin"
    override val pluginOptions = listOf(
        CliOption("enabled", "<true|false>", "Enable the plugin")
    )
}

@OptIn(ExperimentalCompilerApi::class)
class MyCompilerPluginRegistrar : CompilerPluginRegistrar() {
    override val supportsK2 = true

    override fun ExtensionStorage.registerExtensions(configuration: CompilerConfiguration) {
        // Register compiler extensions here
        println("Plugin registered!")
    }
}

val result = KotlinCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("App.kt", """
            class App {
                fun run() = "Running"
            }
        """)
    )
    compilerPluginRegistrars = listOf(MyCompilerPluginRegistrar())
    commandLineProcessors = listOf(MyCommandLineProcessor())
    pluginOptions = listOf(
        PluginOption("com.example.myplugin", "enabled", "true")
    )
    inheritClassPath = true
}.compile()

assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)

```

--------------------------------

### Add KSP Dependency for Kotlin Compile Testing

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/README.md

Include this dependency in your build.gradle file to enable KSP processor testing.

```Groovy
dependencies {
    testImplementation("dev.zacsweers.kctfork:ksp:<version>>")
}
```

--------------------------------

### Assert Compilation Results

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/README.md

Verify compilation exit codes, inspect diagnostic messages, and use reflection to validate generated classes.

```Kotlin
assertThat(result.exitCode).isEqualTo(ExitCode.OK)

// Test diagnostic output of compiler
assertThat(result.messages).contains("My annotation processor was called")

// Load compiled classes and inspect generated code through reflection
val kClazz = result.classLoader.loadClass("KClass")
assertThat(kClazz).hasDeclaredMethods("foo")
```

--------------------------------

### Register Compiler Plugin Registrar

Source: https://github.com/zacsweers/kotlin-compile-testing/blob/main/CHANGELOG.md

Use the compilerPluginRegistrars property to add instances of the new entrypoint API for compiler plugins.

```kotlin
KotlinCompilation().apply {
  compilerPluginRegistrars = listOf(MyCompilerPluginRegistrar())
}
```

--------------------------------

### Kotlin/JS Compilation with IR Backend

Source: https://context7.com/zacsweers/kotlin-compile-testing/llms.txt

Compile Kotlin code to JavaScript using the Kotlin/JS compiler with the IR backend. Configure options like `irProduceJs`, `irDce`, `moduleName`, and `generateDts` for desired output.

```kotlin
import com.tschuchort.compiletesting.KotlinJsCompilation
import com.tschuchort.compiletesting.SourceFile
import org.assertj.core.api.Assertions.assertThat

val result = KotlinJsCompilation().apply {
    sources = listOf(
        SourceFile.kotlin("App.kt", """
            fun greet(name: String): String {
                return "Hello, ${'$'}name!"
            }

            fun main() {
                console.log(greet("World"))
            }
        """)
    )

    // IR backend options
    irProduceJs = true          // Generate JS files
    irProduceKlibFile = false   // Don't produce klib
    irDce = true                // Enable dead code elimination

    // Module configuration
    moduleName = "my-app"
    irModuleName = "my-app"

    // TypeScript declarations
    generateDts = true

    inheritClassPath = true
}.compile()

assertThat(result.exitCode).isEqualTo(KotlinJsCompilation.ExitCode.OK)

// Access generated JS files
val jsFiles = result.jsFiles
jsFiles.forEach { file ->
    println("Generated: ${file.name}")
    if (file.extension == "js") {
        println(file.readText().take(500))
    }
}

```

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