First iteration of gradle: fetching of source directories and classpath

build.gradle

@@ -7,12 +7,12 @@ plugins {
 repositories {
     jcenter()
     mavenLocal()
-    maven {
-        url = 'https://repo.maven.apache.org/maven2'
-    }
+    maven { url = 'https://repo.maven.apache.org/maven2' }
+    maven { url = 'https://repo.gradle.org/gradle/libs-releases' }
 }
 
 dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
     compile files("${System.getProperty('java.home')}/../lib/tools.jar")
     compile 'com.google.code.gson:gson:2.8.6'
     compile 'commons-cli:commons-cli:1.4'
@@ -23,8 +23,9 @@ dependencies {
     compile 'org.slf4j:slf4j-nop:1.7.30'
     implementation 'org.eclipse.lsp4j:org.eclipse.lsp4j:0.9.0'
     implementation 'com.google.guava:guava:29.0-jre'
+    implementation "org.gradle:gradle-tooling-api:6.6.1"
+
     testImplementation 'junit:junit:4.13'
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
 }
 
 application {

src/main/java/lsifjava/ProjectIndexer.java

@@ -32,7 +32,13 @@ public void index() throws IOException {
 
         var indexers = new HashMap<Path, DocumentIndexer>();
         var collector = new FileCollector(projectId, arguments, emitter, indexers);
-        Files.walkFileTree(Paths.get(arguments.projectRoot), collector);
+
+        try(GradleInterface gradleInterface = new GradleInterface(arguments.projectRoot)) {
+            for (Path it : gradleInterface.sourceDirectories()) {
+                Files.walkFileTree(it, collector);
+            }
+        }
+
         var fileManager = new SourceFileManager(indexers.keySet());
 
         for(var indexer : indexers.values()) {

src/main/kotlin/lsifjava/GradleInterface.kt

@@ -0,0 +1,31 @@
+package lsifjava
+
+import org.gradle.tooling.GradleConnector
+import org.gradle.tooling.model.GradleProject
+import org.gradle.tooling.model.eclipse.EclipseProject
+import org.gradle.tooling.model.idea.IdeaProject
+import java.nio.file.Path
+import java.nio.file.Paths
+
+// TODO(nsc) exclusions? subprojects? inter-project dependencies? fml
+class GradleInterface(private val projectDir: String): AutoCloseable {
+    private val projectConnection by lazy {
+        GradleConnector.newConnector().forProjectDirectory(Paths.get(projectDir).toFile()).connect()
+    }
+
+    private val eclipseModel by lazy {
+        projectConnection.getModel(EclipseProject::class.java)
+    }
+
+    fun classpath() = Classpath(eclipseModel.classpath.map { it.file.canonicalPath })
+
+    fun sourceDirectories() = eclipseModel.sourceDirectories.map {
+        Paths.get(eclipseModel.projectDirectory.path, it.path)
+    }
+
+    override fun close() = projectConnection.close()
+}
+
+class Classpath(private val classpaths: Iterable<String>): Iterable<String> by classpaths {
+    override fun toString() = classpaths.joinToString(":")
+}