Improved top level error handling

game/src/main/scala/hexacraft/main/Main.scala

@@ -4,8 +4,7 @@ import hexacraft.infra.os.OSUtils
 
 import org.lwjgl.system.Configuration
 
-import java.io.{File, FileOutputStream, PrintStream}
-import java.time.OffsetDateTime
+import java.io.File
 
 object Main:
   def main(args: Array[String]): Unit =
@@ -14,24 +13,17 @@ object Main:
     val isDebugStr = System.getProperty("hexacraft.debug")
     val isDebug = isDebugStr != null && isDebugStr == "true"
 
-    val window = new MainWindow(isDebug)
+    val saveFolder: File = new File(OSUtils.appdataPath, ".hexacraft")
+
+    val errorHandler = MainErrorLogger.create(!isDebug, saveFolder)
+
+    val window = new MainWindow(isDebug, saveFolder)
     try window.run()
     catch
       case t: Throwable =>
-        if isDebug
-        then t.printStackTrace()
-        else logThrowable(t, window.saveFolder)
+        errorHandler.log(t)
         System.exit(1)
 
-  private def logThrowable(e: Throwable, saveFolder: File): Unit =
-    val now = OffsetDateTime.now()
-    val logFile = new File(saveFolder, s"logs/error_$now.log")
-    logFile.getParentFile.mkdirs()
-    e.printStackTrace(new PrintStream(new FileOutputStream(logFile)))
-    System.err.println(
-      s"The program has crashed. The crash report can be found in: ${logFile.getAbsolutePath}"
-    )
-
   private def setNativesFolder(): Unit =
     var file = new File("lib/natives")
 

game/src/main/scala/hexacraft/main/MainErrorLogger.scala

@@ -0,0 +1,31 @@
+package hexacraft.main
+
+import hexacraft.infra.fs.FileSystem
+
+import java.io.{ByteArrayOutputStream, File, PrintStream}
+import java.time.OffsetDateTime
+
+class MainErrorLogger(saveToFile: Boolean, saveFolder: File, fs: FileSystem) {
+  def log(e: Throwable): Unit = if saveToFile then logToFile(e) else logToConsole(e)
+
+  private def logToConsole(e: Throwable): Unit =
+    e.printStackTrace()
+
+  private def logToFile(e: Throwable): Unit =
+    val byteStream = new ByteArrayOutputStream()
+    e.printStackTrace(new PrintStream(byteStream))
+
+    val now = OffsetDateTime.now()
+    val logFile = new File(saveFolder, s"logs/error_$now.log".replace(':', '.'))
+
+    fs.writeBytes(logFile.toPath, byteStream.toByteArray)
+
+    System.err.println(
+      s"The program has crashed. The crash report can be found in: ${logFile.getAbsolutePath}"
+    )
+}
+
+object MainErrorLogger {
+  def create(saveToFile: Boolean, saveFolder: File): MainErrorLogger =
+    MainErrorLogger(saveToFile, saveFolder, FileSystem.create())
+}

game/src/main/scala/hexacraft/main/MainWindow.scala

@@ -5,7 +5,6 @@ import hexacraft.gui.*
 import hexacraft.gui.comp.GUITransformation
 import hexacraft.infra.fs.FileSystem
 import hexacraft.infra.gpu.OpenGL
-import hexacraft.infra.os.OSUtils
 import hexacraft.infra.window.*
 import hexacraft.renderer.VAO
 import hexacraft.util.{Resource, Result}
@@ -16,9 +15,7 @@ import org.joml.Vector2i
 import java.io.File
 import scala.collection.mutable
 
-class MainWindow(isDebug: Boolean) extends GameWindow:
-  val saveFolder: File = new File(OSUtils.appdataPath, ".hexacraft")
-
+class MainWindow(isDebug: Boolean, saveFolder: File) extends GameWindow:
   private val fs = FileSystem.create()
 
   private val multiplayerEnabled = isDebug
@@ -264,6 +261,6 @@ class MainWindow(isDebug: Boolean) extends GameWindow:
   private def tryQuit(): Unit = window.requestClose()
 
   private def destroy(): Unit =
-    scene.unload()
+    if scene != null then scene.unload()
 
     Resource.freeAllResources()

game/src/test/scala/hexacraft/main/MainErrorLoggerTest.scala

@@ -0,0 +1,99 @@
+package hexacraft.main
+
+import hexacraft.infra.fs.FileSystem
+
+import munit.FunSuite
+
+import java.io.{ByteArrayOutputStream, File, PrintStream}
+import java.nio.file.Path
+
+class MainErrorLoggerTest extends FunSuite {
+  test("does not write log files in debug mode") {
+    val fs = FileSystem.createNull()
+    val tracker = fs.trackWrites()
+
+    val logger = MainErrorLogger(false, null, fs)
+    captureStdErr(logger.log(new Exception("something happened")))
+
+    assertEquals(tracker.events, Seq())
+  }
+
+  test("writes stacktrace to stderr in debug mode") {
+    val fs = FileSystem.createNull()
+    val logger = MainErrorLogger(false, null, fs)
+
+    val output = captureStdErr(logger.log(new Exception("something happened")))
+
+    val lines = output.lines().toList
+    assert(lines.size() > 1)
+    assertEquals(lines.get(0), "java.lang.Exception: something happened")
+  }
+
+  test("write a log file in release mode") {
+    val fs = FileSystem.createNull()
+    val tracker = fs.trackWrites()
+
+    val saveFolder = File("some/path")
+    val logger = MainErrorLogger(true, saveFolder, fs)
+    captureStdErr(logger.log(new Exception("something happened")))
+
+    assertEquals(tracker.events.size, 1)
+    val writeEvent = tracker.events(0)
+
+    val logsFolder = writeEvent.path.getParent
+    assertEquals(logsFolder, Path.of("some/path/logs"))
+
+    val logFileName = writeEvent.path.getFileName.toString
+    assert(logFileName.startsWith("error_"))
+    assert(logFileName.endsWith(".log"))
+
+    val logLines = String(writeEvent.bytes.toArray).lines().toList
+    assert(logLines.size() > 1)
+    assertEquals(logLines.get(0), "java.lang.Exception: something happened")
+  }
+
+  // TODO: the check below should probably live in FileSystem instead
+  // On Windows colons may not be used in file names
+  test("does not use colon in the log file name") {
+    val fs = FileSystem.createNull()
+    val tracker = fs.trackWrites()
+
+    val saveFolder = File("some/path")
+    val logger = MainErrorLogger(true, saveFolder, fs)
+    captureStdErr(logger.log(new Exception("something happened")))
+
+    assertEquals(tracker.events.size, 1)
+
+    val logFile = tracker.events(0).path
+    val logFileName = logFile.getFileName.toString
+    assert(!logFileName.contains(':'), s"'$logFileName' contains a colon")
+  }
+
+  test("writes to stderr to mention the log file in release mode") {
+    val fs = FileSystem.createNull()
+    val tracker = fs.trackWrites()
+
+    val saveFolder = File("some/path")
+    val logger = MainErrorLogger(true, saveFolder, fs)
+
+    val output = captureStdErr(logger.log(new Exception("something happened")))
+
+    assertEquals(tracker.events.size, 1)
+    val writeEvent = tracker.events(0)
+    val logFileAbsolutePath = writeEvent.path.toAbsolutePath.toString
+
+    assert(output.contains(logFileAbsolutePath))
+  }
+
+  def captureStdErr(code: => Unit): String = {
+    val prevErr = System.err
+    try
+      val err = ByteArrayOutputStream()
+      System.setErr(PrintStream(err))
+
+      code
+
+      String(err.toByteArray)
+    finally System.setErr(prevErr)
+  }
+}