Add example to demonstrate how to configure a custom Dokka plugin

build-logic/src/main/kotlin/dokkabuild/utils/SystemPropertyAdder.kt

@@ -153,6 +153,16 @@ abstract class SystemPropertyAdder @Inject internal constructor(
         return task.inputs.property("SystemProperty input property $key", value)
     }
 
+    fun inputProperty(
+        key: String,
+        value: String,
+    ): TaskInputPropertyBuilder {
+        task.jvmArgumentProviders.add(
+            SystemPropertyArgumentProvider(key, value) { it }
+        )
+        return task.inputs.property("SystemProperty input property $key", value)
+    }
+
     @JvmName("inputBooleanProperty")
     fun inputProperty(
         key: String,

build-logic/src/main/kotlin/dokkabuild/utils/strings.kt

@@ -0,0 +1,7 @@
+/*
+ * Copyright 2014-2024 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+package dokkabuild.utils
+
+/** Title case the first char of a string */
+fun String.uppercaseFirstChar(): String = replaceFirstChar(Char::uppercaseChar)

dokka-integration-tests/gradle/build.gradle.kts

@@ -5,8 +5,11 @@
 
 import dokkabuild.tasks.GitCheckoutTask
 import dokkabuild.utils.systemProperty
+import dokkabuild.utils.uppercaseFirstChar
 import org.gradle.api.tasks.PathSensitivity.NAME_ONLY
 import org.gradle.api.tasks.PathSensitivity.RELATIVE
+import kotlin.io.path.listDirectoryEntries
+import kotlin.io.path.name
 
 plugins {
     id("dokkabuild.kotlin-jvm")
@@ -197,10 +200,11 @@ testing {
         }
     }
     val testExampleProjects by suites.registering(JvmTestSuite::class) {
+        val exampleGradleProjectsDir = projectDir.resolve("../../examples/gradle-v2")
+
         targets.configureEach {
-            testTask.configure {
+            testTask {
 
-                val exampleGradleProjectsDir = projectDir.resolve("../../examples/gradle-v2")
                 systemProperty
                     .inputDirectory("exampleGradleProjectsDir", exampleGradleProjectsDir)
                     .withPathSensitivity(RELATIVE)
@@ -215,5 +219,28 @@ testing {
                 systemProperty("junit.jupiter.execution.parallel.mode.default", "CONCURRENT")
             }
         }
+
+        // Register specific Gradle test runs for each example so the examples can be tested individually.
+        exampleGradleProjectsDir.toPath()
+            .listDirectoryEntries()
+            .map { it.name }
+            .filter {
+                it.endsWith("-example")
+                // note: avoid checks like `isDirectory()` to prevent Gradle registering the files as CC inputs.
+            }
+            .forEach { exampleProjectName ->
+                val prettyName = exampleProjectName
+                    .removeSuffix("-example")
+                    .split("-")
+                    .joinToString("") { it.uppercaseFirstChar() }
+
+                targets.register("testExample$prettyName") {
+                    testTask {
+                        description = "Only test $exampleProjectName"
+                        group = "verification - example projects"
+                        systemProperty.inputProperty("exampleProjectFilter", exampleProjectName)
+                    }
+                }
+            }
     }
 }