Add index-dependency command to troubleshoot package repo issues.

Previously, there was no easy way to reproduce issues from indexing
package repos. Now, you can run `lsif-java index-dependency DEPENDENCY`
to unzip the sources of that dependency and index with lsif-java.

Author: olafurpg

lsif-java/src/main/scala/com/sourcegraph/lsif_java/LsifJava.scala

@@ -3,6 +3,7 @@ package com.sourcegraph.lsif_java
 import java.io.PrintStream
 
 import com.sourcegraph.lsif_java.commands.IndexCommand
+import com.sourcegraph.lsif_java.commands.IndexDependencyCommand
 import com.sourcegraph.lsif_java.commands.IndexSemanticdbCommand
 import com.sourcegraph.lsif_java.commands.SnapshotCommand
 import com.sourcegraph.lsif_java.commands.SnapshotLsifCommand
@@ -21,6 +22,7 @@ object LsifJava {
       CommandParser[VersionCommand],
       CommandParser[IndexCommand],
       CommandParser[IndexSemanticdbCommand],
+      CommandParser[IndexDependencyCommand],
       CommandParser[SnapshotCommand],
       CommandParser[SnapshotLsifCommand]
     )

lsif-java/src/main/scala/com/sourcegraph/lsif_java/commands/IndexDependencyCommand.scala

@@ -0,0 +1,100 @@
+package com.sourcegraph.lsif_java.commands
+
+import java.nio.charset.StandardCharsets
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.Paths
+import java.nio.file.StandardCopyOption
+import java.nio.file.StandardOpenOption
+import java.util.jar.JarFile
+
+import com.sourcegraph.io.AbsolutePath
+import com.sourcegraph.lsif_java.Dependencies
+import com.sourcegraph.lsif_semanticdb.JavaVersion
+import moped.cli.Command
+import moped.cli.CommandParser
+
+final case class IndexDependencyCommand(
+    target: Path = Paths.get("maven"),
+    index: IndexCommand = IndexCommand(),
+    dependency: String = ""
+) extends Command {
+  def app = index.app
+  private val absoluteTarget = AbsolutePath
+    .of(target, app.env.workingDirectory)
+    .resolve(dependency.replace(":", "__"))
+  def run(): Int = {
+    if (dependency == "") {
+      app.reporter.error("dependency can't be empty")
+      1
+    } else {
+      val deps = Dependencies
+        .resolveDependencies(List(dependency), transitive = false)
+      deps.sources.headOption match {
+        case Some(sources) =>
+          unzipJar(sources)
+          deps.classpath.headOption match {
+            case Some(classpath) =>
+              Option(
+                JavaVersion.classfileJvmVersion(classpath).orElse(8)
+              ) match {
+                case Some(jvmVersion) =>
+                  val config =
+                    s"""{"kind":"maven","jvm":"$jvmVersion","dependencies":["$dependency"]}"""
+                  Files.createDirectories(absoluteTarget)
+                  Files.write(
+                    absoluteTarget.resolve("lsif-java.json"),
+                    config.getBytes(StandardCharsets.UTF_8),
+                    StandardOpenOption.CREATE,
+                    StandardOpenOption.TRUNCATE_EXISTING
+                  )
+                  index
+                    .copy(
+                      buildTool = Some("lsif"),
+                      app = app
+                        .withEnv(app.env.withWorkingDirectory(absoluteTarget))
+                    )
+                    .run()
+                case None =>
+                  app
+                    .reporter
+                    .error(
+                      s"failed to infer JVM version for classpath '$classpath'"
+                    )
+                  1
+              }
+            case None =>
+              app.reporter.error(s"no classpath for dependency '$dependency'")
+              1
+          }
+        case None =>
+          app.reporter.error(s"no sources for dependency '$dependency'")
+          1
+      }
+      1
+    }
+  }
+
+  private def unzipJar(file: Path): Unit = {
+    val jar = new JarFile(file.toFile())
+    try {
+      val entries = jar.entries()
+      while (entries.hasMoreElements()) {
+        val entry = entries.nextElement()
+        if (!entry.isDirectory()) {
+          val out = absoluteTarget.resolve(entry.getName())
+          Files.createDirectories(out.getParent())
+          val in = jar.getInputStream(entry)
+          try Files.copy(in, out, StandardCopyOption.REPLACE_EXISTING)
+          finally in.close()
+        }
+      }
+    } finally {
+      jar.close()
+    }
+  }
+}
+
+object IndexDependencyCommand {
+  implicit val parser = CommandParser.derive(IndexDependencyCommand())
+}