Improved show output to be valid JSON and added showNamed

docs/antora/modules/ROOT/pages/Intro_to_Mill.adoc

@@ -660,6 +660,46 @@ $ mill show foo.compileClasspath
 `show` is also useful for interacting with Mill from external tools, since the JSON it outputs is structured and easily
 parsed and manipulated.
 
+When `show` is used with multiple targets, it's output will slightly change to a JSON array, containing all the results of the given targets.
+
+[source,bash]
+----
+$ mill show "foo.{sources,compileClasspath}"
+[1/1] show
+[2/11] foo.resources
+[
+  [
+    "ref:8befb7a8:/Users/lihaoyi/Dropbox/Github/test/foo/src"
+  ],
+  [
+    "ref:c984eca8:/Users/lihaoyi/Dropbox/Github/test/foo/resources",
+    ".../org/scala-lang/scala-library/2.13.1/scala-library-2.13.1.jar"
+  ]
+]
+----
+
+=== showNamed
+
+Same as `show`, but the output will always be structured in a JSON dictionary, with the task names as key and the task results as JSON values.
+
+[source,bash]
+----
+$ mill showNamed "foo.{sources,compileClasspath}"
+[1/1] show
+[2/11] foo.resources
+{
+  "foo.sources":
+  [
+    "ref:8befb7a8:/Users/lihaoyi/Dropbox/Github/test/foo/src"
+  ],
+  "foo.compileClasspath":
+  [
+    "ref:c984eca8:/Users/lihaoyi/Dropbox/Github/test/foo/resources",
+    ".../org/scala-lang/scala-library/2.13.1/scala-library-2.13.1.jar"
+  ]
+}
+----
+
 === path
 
 [source,bash]

main/src/mill/main/MainModule.scala

@@ -2,12 +2,13 @@ package mill.main
 
 import java.util.concurrent.LinkedBlockingQueue
 import mill.{BuildInfo, T}
-import mill.api.{Ctx, PathRef, Result}
+import mill.api.{Ctx, PathRef, Result, internal}
 import mill.define.{Command, NamedTask, Task}
 import mill.eval.{Evaluator, EvaluatorPaths}
 import mill.util.{PrintLogger, Watched}
 import mill.define.SelectMode
 import pprint.{Renderer, Truncated}
+import ujson.Value
 
 object MainModule {
   @deprecated(
@@ -56,6 +57,21 @@ object MainModule {
         Result.Success(Watched((), watched))
     }
   }
+
+  @internal
+  def evaluateTasksNamed[T](
+      evaluator: Evaluator,
+      targets: Seq[String],
+      selectMode: SelectMode
+  )(f: Seq[(Any, Option[(RunScript.TaskName, ujson.Value)])] => T): Result[Watched[Option[T]]] = {
+    RunScript.evaluateTasksNamed(evaluator, targets, selectMode) match {
+      case Left(err) => Result.Failure(err)
+      case Right((watched, Left(err))) => Result.Failure(err, Some(Watched(None, watched)))
+      case Right((watched, Right(res))) =>
+        val fRes = f(res)
+        Result.Success(Watched(Some(fRes), watched))
+    }
+  }
 }
 
 trait MainModule extends mill.Module {
@@ -235,8 +251,8 @@ trait MainModule extends mill.Module {
    * Runs a given task and prints the JSON result to stdout. This is useful
    * to integrate Mill into external scripts and tooling.
    */
-  def show(evaluator: Evaluator, targets: String*) = T.command {
-    MainModule.evaluateTasks(
+  def show(evaluator: Evaluator, targets: String*): Command[Value] = T.command {
+    MainModule.evaluateTasksNamed(
       evaluator.withBaseLogger(
         // When using `show`, redirect all stdout of the evaluated tasks so the
         // printed JSON is the only thing printed to stdout.
@@ -248,10 +264,44 @@ trait MainModule extends mill.Module {
       ),
       targets,
       SelectMode.Separated
-    ) { res =>
-      for (json <- res.flatMap(_._2)) {
-        T.log.outputStream.println(json.render(indent = 4))
-      }
+    ) { res: Seq[(Any, Option[(String, ujson.Value)])] =>
+      val jsons = res.flatMap(_._2).map(_._2)
+      val output: ujson.Value =
+        if (jsons.size == 1) jsons.head
+        else { ujson.Arr.from(jsons) }
+      T.log.outputStream.println(output.render(indent = 2))
+      output
+    }.map { res =>
+      val Watched(Some(json), _) = res
+      json
+    }
+  }
+
+  /**
+   * Runs a given task and prints the results as JSON dictionary to stdout. This is useful
+   * to integrate Mill into external scripts and tooling.
+   */
+  def showNamed(evaluator: Evaluator, targets: String*): Command[Value] = T.command {
+    MainModule.evaluateTasksNamed(
+      evaluator.withBaseLogger(
+        // When using `show`, redirect all stdout of the evaluated tasks so the
+        // printed JSON is the only thing printed to stdout.
+        evaluator.baseLogger match {
+          case PrintLogger(c1, d, c2, c3, _, i, e, in, de, uc) =>
+            PrintLogger(c1, d, c2, c3, e, i, e, in, de, uc)
+          case l => l
+        }
+      ),
+      targets,
+      SelectMode.Separated
+    ) { res: Seq[(Any, Option[(String, ujson.Value)])] =>
+      val nameAndJson = res.flatMap(_._2)
+      val output: ujson.Value = ujson.Obj.from(nameAndJson)
+      T.log.outputStream.println(output.render(indent = 2))
+      output
+    }.map { res =>
+      val Watched(Some(json), _) = res
+      json
     }
   }
 

main/src/mill/main/MainRunner.scala

@@ -49,7 +49,6 @@ class MainRunner(
   var stateCache = stateCache0
 
   override def watchAndWait(watched: Seq[(ammonite.interp.Watchable, Long)]) = {
-
     setIdle(true)
     super.watchAndWait(watched)
     setIdle(false)
@@ -86,7 +85,7 @@ class MainRunner(
   val colored = config.core.color.getOrElse(mainInteractive)
 
   override val colors = if (colored) Colors.Default else Colors.BlackWhite
-  override def runScript(scriptPath: os.Path, scriptArgs: List[String]) =
+  override def runScript(scriptPath: os.Path, scriptArgs: List[String]): Boolean =
     watchLoop2(
       isRepl = false,
       printing = true,

main/src/mill/main/RunScript.scala

@@ -17,13 +17,17 @@ import mill.internal.AmmoniteUtils
 import scala.collection.mutable
 import scala.reflect.ClassTag
 import mill.define.ParseArgs.TargetsWithParams
+import ujson.Value
 
 /**
  * Custom version of ammonite.main.Scripts, letting us run the build.sc script
  * directly without going through Ammonite's main-method/argument-parsing
  * subsystem
  */
 object RunScript {
+
+  type TaskName = String
+
   def runScript(
       home: os.Path,
       wd: os.Path,
@@ -319,11 +323,45 @@ object RunScript {
       }
   }
 
+  def evaluateTasksNamed[T](
+      evaluator: Evaluator,
+      scriptArgs: Seq[String],
+      selectMode: SelectMode
+  ): Either[String, (Seq[PathRef], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]])] = {
+    for (targets <- resolveTasks(mill.main.ResolveTasks, evaluator, scriptArgs, selectMode))
+      yield {
+        val (watched, res) = evaluateNamed(evaluator, Agg.from(targets.distinct))
+
+        val watched2 = for {
+          x <- res.toSeq
+          (Watched(_, extraWatched), _) <- x
+          w <- extraWatched
+        } yield w
+
+        (watched ++ watched2, res)
+      }
+  }
+
   def evaluate(
       evaluator: Evaluator,
       targets: Agg[Task[Any]]
   ): (Seq[PathRef], Either[String, Seq[(Any, Option[ujson.Value])]]) = {
-    val evaluated = evaluator.evaluate(targets)
+    val (watched, results) = evaluateNamed(evaluator, targets)
+    // we drop the task name in the inner tuple
+    (watched, results.map(_.map(p => (p._1, p._2.map(_._2)))))
+  }
+
+  /**
+   *
+   * @param evaluator
+   * @param targets
+   * @return (watched-paths, Either[err-msg, Seq[(task-result, Option[(task-name, task-return-as-json)])]])
+   */
+  def evaluateNamed(
+      evaluator: Evaluator,
+      targets: Agg[Task[Any]]
+  ): (Seq[PathRef], Either[String, Seq[(Any, Option[(TaskName, ujson.Value)])]]) = {
+    val evaluated: Evaluator.Results = evaluator.evaluate(targets)
     val watched = evaluated.results
       .iterator
       .collect {
@@ -337,18 +375,18 @@ object RunScript {
 
     evaluated.failing.keyCount match {
       case 0 =>
-        val json = for (t <- targets.toSeq) yield {
+        val nameAndJson = for (t <- targets.toSeq) yield {
           t match {
             case t: mill.define.NamedTask[_] =>
               val jsonFile = EvaluatorPaths.resolveDestPaths(evaluator.outPath, t).meta
               val metadata = upickle.default.read[Evaluator.Cached](ujson.read(jsonFile.toIO))
-              Some(metadata.value)
+              Some(t.toString, metadata.value)
 
             case _ => None
           }
         }
 
-        watched -> Right(evaluated.values.zip(json))
+        watched -> Right(evaluated.values.zip(nameAndJson))
       case n => watched -> Left(s"$n targets failed\n$errorStr")
     }
   }

main/test/src/main/MainModuleTests.scala

@@ -0,0 +1,81 @@
+package mill.main
+
+import mill.api.Result
+import mill.{Agg, T}
+import mill.util.{TestEvaluator, TestUtil}
+import utest.{TestSuite, Tests, test}
+
+object MainModuleTests extends TestSuite {
+
+  object mainModule extends TestUtil.BaseModule with MainModule {
+    def hello = T { Seq("hello", "world") }
+    def hello2 = T { Map("1" -> "hello", "2" -> "world") }
+  }
+
+  override def tests: Tests = Tests {
+    test("show") {
+      val evaluator = new TestEvaluator(mainModule)
+      test("single") {
+        val results =
+          evaluator.evaluator.evaluate(Agg(mainModule.show(evaluator.evaluator, "hello")))
+
+        assert(results.failing.keyCount == 0)
+
+        val Result.Success(value) = results.rawValues.head
+
+        assert(value == ujson.Arr.from(Seq("hello", "world")))
+      }
+      test("multi") {
+        val results =
+          evaluator.evaluator.evaluate(Agg(mainModule.show(
+            evaluator.evaluator,
+            "hello",
+            "+",
+            "hello2"
+          )))
+
+        assert(results.failing.keyCount == 0)
+
+        val Result.Success(value) = results.rawValues.head
+
+        assert(value == ujson.Arr.from(Seq(
+          ujson.Arr.from(Seq("hello", "world")),
+          ujson.Obj.from(Map("1" -> "hello", "2" -> "world"))
+        )))
+      }
+    }
+    test("showNamed") {
+      val evaluator = new TestEvaluator(mainModule)
+      test("single") {
+        val results =
+          evaluator.evaluator.evaluate(Agg(mainModule.showNamed(evaluator.evaluator, "hello")))
+
+        assert(results.failing.keyCount == 0)
+
+        val Result.Success(value) = results.rawValues.head
+
+        assert(value == ujson.Obj.from(Map(
+          "hello" -> ujson.Arr.from(Seq("hello", "world"))
+        )))
+      }
+      test("multi") {
+        val results =
+          evaluator.evaluator.evaluate(Agg(mainModule.showNamed(
+            evaluator.evaluator,
+            "hello",
+            "+",
+            "hello2"
+          )))
+
+        assert(results.failing.keyCount == 0)
+
+        val Result.Success(value) = results.rawValues.head
+
+        assert(value == ujson.Obj.from(Map(
+          "hello" -> ujson.Arr.from(Seq("hello", "world")),
+          "hello2" -> ujson.Obj.from(Map("1" -> "hello", "2" -> "world"))
+        )))
+      }
+    }
+  }
+}