repl: don't truncate output by default, and allow to configure it (via maxHeight) (#56)

Author: mpollmeier

README.md

@@ -16,6 +16,7 @@ Scala REPL PlusPlus: a better Scala 3 REPL. With many features inspired by ammon
 - [REPL](#repl)
   * [Add dependencies with maven coordinates](#add-dependencies-with-maven-coordinates)
   * [Importing additional script files interactively](#importing-additional-script-files-interactively)
+  * [Rendering of output](#rendering-of-output)
 - [Scripting](#scripting)
   * [Simple "Hello world" script](#simple-hello-world-script)
   * [Predef file(s) used in script](#predef-files-used-in-script)
@@ -32,7 +33,6 @@ Scala REPL PlusPlus: a better Scala 3 REPL. With many features inspired by ammon
 - [Limitations / Debugging](#limitations--debugging)
   * [Why are script line numbers incorrect?](#why-are-script-line-numbers-incorrect)
 - [Parameters cheat sheet: the most important ones](#parameters-cheat-sheet-the-most-important-ones)
-
 ## Benefits over / comparison with
 
 ### Regular Scala REPL
@@ -113,6 +113,19 @@ val foo = 1
 println(bar) //1
 ```
 
+### Rendering of output
+
+Unlike the stock Scala REPL, scala-repl-pp does _not_ truncate the output by default. You can optionally specify the maxHeight parameter though:
+```
+./scala-repl-pp --maxHeight 5
+scala> (1 to 100000).toSeq
+val res0: scala.collection.immutable.Range.Inclusive = Range(
+  1,
+  2,
+  3,
+...
+```
+
 ## Scripting
 
 See [ScriptRunnerTest](core/src/test/scala/replpp/scripting/ScriptRunnerTest.scala) for a more complete and in-depth overview.

core/src/main/scala/replpp/Config.scala

@@ -11,8 +11,9 @@ case class Config(
 
   // repl only
   prompt: Option[String] = None,
-  greeting: String = "Welcome to the scala-repl-pp!",
+  greeting: String = "Welcome to scala-repl-pp!",
   onExitCode: Option[String] = None,
+  maxHeight: Option[Int] = None,
 
   // script only
   scriptFile: Option[Path] = None,
@@ -46,6 +47,10 @@ case class Config(
       add("--repo", resolver)
     }
 
+    maxHeight.foreach { value =>
+      add("--maxHeight", s"$value")
+    }
+
     scriptFile.foreach(file => add("--script", file.toString))
     command.foreach(cmd => add("--command", cmd))
 
@@ -100,14 +105,18 @@ object Config {
         .text("specify a custom prompt")
 
       opt[String]("greeting")
-        .valueName("Welcome to the scala-repl-pp!")
+        .valueName("Welcome to scala-repl-pp!")
         .action((x, c) => c.copy(greeting = x))
         .text("specify a custom greeting")
 
       opt[String]("onExitCode")
         .valueName("""println("bye!")""")
         .action((x, c) => c.copy(onExitCode = Option(x)))
 
+      opt[Int]("maxHeight")
+        .action((x, c) => c.copy(maxHeight = Some(x)))
+        .text("Maximum number lines to print before output gets truncated (default: no limit)")
+
       note("Script execution")
 
       opt[Path]("script")

core/src/main/scala/replpp/InteractiveShell.scala

@@ -17,7 +17,7 @@ object InteractiveShell {
       onExitCode = config.onExitCode,
       greeting = Option(config.greeting),
       prompt = config.prompt.getOrElse("scala"),
-      maxPrintElements = Int.MaxValue
+      maxHeight = config.maxHeight
     )
 
     val initialState: State = replDriver.initialState

core/src/main/scala/replpp/PPrinter.scala

@@ -4,14 +4,24 @@ import pprint.{PPrinter, Renderer, Result, Tree, Truncated}
 import scala.util.matching.Regex
 
 object PPrinter {
-  private val pprinter = create()
+  private var pprinter: pprint.PPrinter = null
+  private var maxHeight: Int = Int.MaxValue
 
-  def apply(obj: Object): String =
-    pprinter(obj).toString
+  def apply(objectToRender: Object, maxHeight: Int = Int.MaxValue): String = {
+    val _pprinter = this.synchronized {
+      // initialise on first use and whenever the maxHeight setting changed
+      if (pprinter == null || this.maxHeight != maxHeight) {
+        pprinter = create(maxHeight)
+        this.maxHeight = maxHeight
+      }
+      pprinter
+    }
+    _pprinter.apply(objectToRender).render
+  }
 
-  private def create(): pprint.PPrinter = {
+  private def create(maxHeight: Int): pprint.PPrinter = {
     new pprint.PPrinter(
-      defaultHeight = 99999,
+      defaultHeight = maxHeight,
       colorLiteral = fansi.Attrs.Empty, // leave color highlighting to the repl
       colorApplyPrefix = fansi.Attrs.Empty) {
 

core/src/main/scala/replpp/ReplDriver.scala

@@ -27,7 +27,7 @@ class ReplDriver(args: Array[String],
                  onExitCode: Option[String] = None,
                  greeting: Option[String],
                  prompt: String,
-                 maxPrintElements: Int,
+                 maxHeight: Option[Int] = None,
                  classLoader: Option[ClassLoader] = None) extends dotty.tools.repl.ReplDriver(args, out, classLoader) {
 
   /** Run REPL with `state` until `:quit` command found
@@ -124,9 +124,10 @@ class ReplDriver(args: Array[String],
       // classloader, so we use reflection instead of simply calling `replpp.PPrinter:apply`.
       // This is analogous to what happens in dotty.tools.repl.Rendering.
       val pprinter = Class.forName("replpp.PPrinter", true, rendering.myClassLoader)
-      val renderer = pprinter.getMethod("apply", classOf[Object])
-      (value: Object, maxElements: Int, maxCharacters: Int) =>
-        renderer.invoke(null, value).asInstanceOf[String].take(maxCharacters)
+      val renderingMethod = pprinter.getMethod("apply", classOf[Object], classOf[Int])
+      (objectToRender: Object, maxElements: Int, maxCharacters: Int) => {
+        renderingMethod.invoke(null, objectToRender, maxHeight.getOrElse(Int.MaxValue)).asInstanceOf[String]
+      }
     }
   }
 

core/src/main/scala/replpp/package.scala

@@ -36,6 +36,7 @@ package object replpp {
     compilerArgs += "-explain" // verbose scalac error messages
     compilerArgs += "-deprecation"
     if (config.nocolors) compilerArgs ++= Array("-color", "never")
+
     compilerArgs.result()
   }
 

core/src/test/scala/replpp/ConfigTests.scala

@@ -16,6 +16,7 @@ class ConfigTests extends AnyWordSpec with Matchers {
       verbose = true,
       dependencies = Seq("com.michaelpollmeier:versionsort:1.0.7", "foo:bar:1.2.3"),
       resolvers = Seq(apacheRepo, sonatypeRepo),
+      maxHeight = Some(10000),
       scriptFile = Some(Paths.get("/some/script.sc")),
       command = Some("someCommand"),
       params = Map("param1" -> "value1", "param2" -> "222", "someEquation" -> "40 + 2 = 42"),
@@ -31,6 +32,7 @@ class ConfigTests extends AnyWordSpec with Matchers {
       "--dep", "foo:bar:1.2.3",
       "--repo", apacheRepo,
       "--repo", sonatypeRepo,
+      "--maxHeight", "10000",
       "--script", "/some/script.sc",
       "--command", "someCommand",
       "--param", "param1=value1",