Add a FindPlugsTask which does the finding.

Author: nedtwigg

atplug-plugin-gradle/src/main/java/com/diffplug/atplug/tooling/gradle/FindPlugsTask.kt

@@ -0,0 +1,77 @@
+package com.diffplug.atplug.tooling.gradle
+
+import com.diffplug.atplug.tooling.PlugParser
+import java.io.File
+import java.nio.charset.StandardCharsets
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.file.DirectoryProperty
+import org.gradle.api.tasks.*
+import org.gradle.work.*
+
+/**
+ * Incrementally scans compiled classes for @Plug usage and writes discovered plug classes into an
+ * output directory.
+ */
+@CacheableTask
+abstract class FindPlugsTask : DefaultTask() {
+	@get:CompileClasspath
+	@get:Incremental
+	@get:InputFiles
+	abstract val classesFolders: ConfigurableFileCollection
+
+	/** Directory where we will store discovered plugs in .txt files, etc. */
+	@get:OutputDirectory abstract val discoveredPlugsDir: DirectoryProperty
+
+	@TaskAction
+	fun findPlugs(inputChanges: InputChanges) {
+		// If not incremental, clear everything and rescan
+		if (!inputChanges.isIncremental) {
+			discoveredPlugsDir.get().asFile.deleteRecursively()
+		}
+
+		// Make sure our output directory exists
+		discoveredPlugsDir.get().asFile.mkdirs()
+
+		// For each changed file in classesFolders, determine if it has @Plug
+		for (change in inputChanges.getFileChanges(classesFolders)) {
+			if (!change.file.name.endsWith(".class")) {
+				continue
+			}
+			when (change.changeType) {
+				ChangeType.REMOVED -> {
+					// Remove old discovered data for this file
+					removeOldMetadata(change.file)
+				}
+				ChangeType.ADDED,
+				ChangeType.MODIFIED -> {
+					parseAndWriteMetadata(change.file)
+				}
+			}
+		}
+	}
+
+	private fun parseAndWriteMetadata(classFile: File) {
+		val parser = PlugParser()
+		parser.parse(classFile)
+		if (parser.hasPlug()) {
+			// For example: write a single line containing the discovered plug FQN
+			val discoveredFile = discoveredPlugsDir.file(parser.plugClassName + ".txt").get().asFile
+			discoveredFile.parentFile.mkdirs()
+			discoveredFile.writeText(
+					parser.plugClassName!! + "|" + parser.socketClassName!!, StandardCharsets.UTF_8)
+		} else {
+			// If previously discovered, remove it
+			removeOldMetadata(classFile)
+		}
+	}
+
+	private fun removeOldMetadata(classFile: File) {
+		// Remove any discovered file for the old .class
+		val possibleName = classFile.nameWithoutExtension + ".txt"
+		val discoveredFile = discoveredPlugsDir.file(possibleName).get().asFile
+		if (discoveredFile.exists()) {
+			discoveredFile.delete()
+		}
+	}
+}