[2.x] feat: dependencyLicenseInfo (#8506)

* Add JSON output support to dependencyLicenseInfo

- Add LicenseInfo rendering object with text and JSON output
- Add dependencyLicenseInfo input task key
- Implement dependencyLicenseInfo task with JSON format support
- Supports --out option for file output
- Auto-detects JSON format from .json file extension
- Follows same pattern as dependencyTree task

Resolves #7771

main/src/main/scala/sbt/internal/graph/rendering/LicenseInfo.scala

@@ -0,0 +1,50 @@
+/*
+ * sbt
+ * Copyright 2023, Scala center
+ * Copyright 2011 - 2022, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt
+package internal
+package graph
+package rendering
+
+import sbt.internal.graph.*
+
+object LicenseInfo {
+  def render(graph: ModuleGraph): String =
+    graph.nodes
+      .filter(_.isUsed)
+      .groupBy(_.license)
+      .toSeq
+      .sortBy(_._1)
+      .map { case (license, modules) =>
+        license.getOrElse("No license specified") + "\n" +
+          modules.map(m => s"\t ${m.id.idString}").mkString("\n")
+      }
+      .mkString("\n\n")
+
+  def renderJson(graph: ModuleGraph): String = {
+    // Create JSON array manually: [{license: "...", modules: [...]}, ...]
+    def escapeJson(str: String): String =
+      str.replace("\\", "\\\\").replace("\"", "\\\"").replace("\n", "\\n").replace("\r", "\\r")
+
+    def formatModuleList(modules: Vector[String]): String =
+      modules.map(m => s""""${escapeJson(m)}"""").mkString("[", ",", "]")
+
+    val groups = graph.nodes
+      .filter(_.isUsed)
+      .groupBy(_.license)
+      .toSeq
+      .sortBy(_._1)
+      .map { case (license, modules) =>
+        val licenseStr = license.getOrElse("No license specified")
+        val moduleList = formatModuleList(modules.map(_.id.idString).toVector.sorted)
+        s"""{"license":"${escapeJson(licenseStr)}","modules":$moduleList}"""
+      }
+
+    groups.mkString("[", ",", "]")
+  }
+}

main/src/main/scala/sbt/plugins/DependencyTreeKeys.scala

@@ -34,6 +34,8 @@ abstract class DependencyTreeKeys:
   private[sbt] val dependencyTreeModuleGraphStore =
     taskKey[ModuleGraph]("The stored module-graph from the last run")
   val whatDependsOn = inputKey[String]("Shows information about what depends on the given module")
+  val dependencyLicenseInfo =
+    inputKey[String]("Displays license information for dependencies in text or JSON format")
   private[sbt] val dependencyTreeCrossProjectId = settingKey[ModuleID]("")
 
   // 0 was added to avoid conflict with sbt-dependency-tree

main/src/main/scala/sbt/plugins/DependencyTreeSettings.scala

@@ -254,8 +254,52 @@ OPTIONS
         }
         output
       },
+      dependencyLicenseInfo := (Def.inputTaskDyn {
+        val s = streams.value
+        val args = ArgsParser.parsed.toList
+        val isHelp = args.contains(Arg.Help)
+        val isQuiet = args.contains(Arg.Quiet)
+        if isHelp then Def.task { s.log.info(licenseInfoUsageText); "" }
+        else
+          val formatOpt = (args
+            .collect { case Arg.Format(fmt) => fmt })
+            .reverse
+            .headOption
+          val outFileNameOpt = (args
+            .collect { case Arg.Out(out) => out })
+            .reverse
+            .headOption
+          val outFileOpt = outFileNameOpt.map(new File(_))
+          val format = (formatOpt, outFileNameOpt) match
+            case (None, Some(out)) if out.endsWith(".json") => Fmt.Json
+            case (Some(fmt), _)                             => fmt
+            case _                                          => Fmt.Tree
+          Def.task {
+            val graph = dependencyTreeModuleGraph0.value
+            val output = format match
+              case Fmt.Json => rendering.LicenseInfo.renderJson(graph)
+              case _        => rendering.LicenseInfo.render(graph)
+            handleOutput(output, outFileOpt, isQuiet, s.log)
+          }
+      }).evaluated,
     )
 
+  def licenseInfoUsageText: String =
+    s"""dependencyLicenseInfo task displays license information for dependencies.
+
+USAGE
+  dependencyLicenseInfo [subcommand] [options]
+
+SUBCOMMAND
+  json         Prints JSON (default is text)
+  help         Prints this help
+
+OPTIONS
+  --quiet      Returns the output as task value
+  --out <file> Writes the output to the specified file;
+               The file extension will influence the default subcommand
+"""
+
   private def handleOutput(
       content: String,
       outputFileOpt: Option[File],

sbt-app/src/sbt-test/dependency-graph/license-info/build.sbt

@@ -0,0 +1,30 @@
+name := "license-info-test"
+scalaVersion := "3.3.1"
+
+libraryDependencies += "org.scala-lang" % "scala-library" % scalaVersion.value
+
+TaskKey[Unit]("check") := {
+  import java.io.File
+  import sbt.io.IO
+  
+  // Check text file
+  val textFile = new File("target/licenses.txt")
+  require(textFile.exists(), s"Text file ${textFile.getPath} does not exist")
+  val textContent = IO.read(textFile)
+  require(textContent.nonEmpty, "Text file is empty")
+  require(textContent.contains("scala-library") || textContent.contains("No license specified"), 
+    "Text file should contain license information")
+  
+  // Check JSON file
+  val jsonFile = new File("target/licenses.json")
+  require(jsonFile.exists(), s"JSON file ${jsonFile.getPath} does not exist")
+  val jsonContent = IO.read(jsonFile)
+  require(jsonContent.nonEmpty, "JSON file is empty")
+  require(jsonContent.trim.startsWith("[") && jsonContent.trim.endsWith("]"), 
+    "JSON file should be a valid JSON array")
+  require(jsonContent.contains("\"license\"") && jsonContent.contains("\"modules\""), 
+    "JSON file should contain license and modules fields")
+  
+  ()
+}
+

sbt-app/src/sbt-test/dependency-graph/license-info/test

@@ -0,0 +1,8 @@
+# Test dependencyLicenseInfo text output
+> dependencyLicenseInfo --out target/licenses.txt
+$ exists target/licenses.txt
+# Test dependencyLicenseInfo JSON output
+> dependencyLicenseInfo json --out target/licenses.json
+$ exists target/licenses.json
+> check
+