[terminal] IJPL-176473 fix race when cancelling content updates might leave the last output pending/unapplied

The problem is that `TerminalOutputChangesTracker` state is already updated, so `collectChangedOutputOrNull` sees the updated state, and therefore the pending/unapplied output is lost.

`BlockTerminalCommandExecutionTest.commands are executed in order` is fixed now. Previously, it was flacky and the failure could be reproduced when running with "Repeat: Until failure".

GitOrigin-RevId: 2f2431f930e15d5ef54ef62f1b9b13b90df72ae9

plugins/terminal/src/org/jetbrains/plugins/terminal/block/output/TerminalOutputChangesTracker.kt

@@ -63,6 +63,10 @@ internal class TerminalOutputChangesTracker(
 
   private val changeListeners: MutableList<() -> Unit> = CopyOnWriteArrayList()
 
+  @Volatile
+  var pendingOutput: PartialCommandOutput? = null
+    private set
+
   init {
     val listener = object : TextBufferChangesListener {
       override fun linesChanged(fromIndex: Int) = textBuffer.withLock {
@@ -175,7 +179,9 @@ internal class TerminalOutputChangesTracker(
     isAnyLineChanged = false
     isChangesDiscarded = false
 
-    return PartialCommandOutput(output.text, output.styleRanges, logicalLineIndex, textBuffer.width, anyDiscarded)
+    return PartialCommandOutput(output.text, output.styleRanges, logicalLineIndex, textBuffer.width, anyDiscarded).also {
+      pendingOutput = it
+    }
   }
 
   /**
@@ -190,4 +196,8 @@ internal class TerminalOutputChangesTracker(
     }
     return count
   }
+
+  internal fun onOutputApplied() {
+    pendingOutput = null
+  }
 }

plugins/terminal/src/org/jetbrains/plugins/terminal/block/output/TerminalOutputContentUpdatesScheduler.kt

@@ -56,6 +56,7 @@ internal class TerminalOutputContentUpdatesScheduler(
         val partialChange = tracker.collectChangedOutputOrWait()
 
         scheduleChangeApplying(partialChange).join()
+        tracker.onOutputApplied()
       }
     }
 
@@ -73,13 +74,16 @@ internal class TerminalOutputContentUpdatesScheduler(
     }
   }
 
-  fun finishUpdating(): PartialCommandOutput? = textBuffer.withLock {
+  fun finishUpdating(): List<PartialCommandOutput> = textBuffer.withLock {
     val tracker = changesTracker ?: error("Finish updating called before start updating")
     changesTracker = null
     updatingJob?.cancel()
     finished = true
 
-    tracker.collectChangedOutputOrNull()
+    // Not-null `tracker.pendingOutput` means that it was either not applied due to
+    // cancellation or is being applied right now on EDT.
+    // If the latter, it won't hurt to apply it twice.
+    return listOfNotNull(tracker.pendingOutput, tracker.collectChangedOutputOrNull())
   }
 
   private val metricTextInBufferToTextVisible = ActionCoordinator<Unit, TimeMark>(

plugins/terminal/src/org/jetbrains/plugins/terminal/block/output/TerminalOutputController.kt

@@ -145,7 +145,7 @@ internal class TerminalOutputController(
 
   private fun scheduleLastOutputUpdate() {
     val contentUpdatesScheduler = runningCommandInteractivity?.contentUpdatesScheduler
-    val lastOutput: PartialCommandOutput? = if (contentUpdatesScheduler?.finished == false) {
+    val lastOutput: List<PartialCommandOutput> = if (contentUpdatesScheduler?.finished == false) {
       contentUpdatesScheduler.finishUpdating()
     }
     else {
@@ -155,18 +155,19 @@ internal class TerminalOutputController(
       val (output, terminalWidth) = session.model.withContentLock {
         ShellCommandOutputScraperImpl.scrapeOutput(session) to session.model.width
       }
-      PartialCommandOutput(
+      listOf(PartialCommandOutput(
         output.text,
         output.styleRanges,
         logicalLineIndex = 0,
         terminalWidth,
         isChangesDiscarded = false,
-      )
+      ))
     }
-
-    if (lastOutput != null) {
+    if (lastOutput.isNotEmpty()) {
       invokeLater(editor.getDisposed(), ModalityState.any()) {
-        updateCommandOutput(lastOutput)
+        for (output in lastOutput) {
+          updateCommandOutput(output)
+        }
       }
     }
   }

plugins/terminal/tests/org/jetbrains/plugins/terminal/block/BlockTerminalCommandExecutionTest.kt

@@ -64,7 +64,7 @@ internal class BlockTerminalCommandExecutionTest(private val shellPath: Path) {
     expected.forEach {
       session.commandExecutionManager.sendCommandToExecute(it.command)
     }
-    awaitBlocksFinalized(view.outputView.controller.outputModel, count)
+    awaitBlocksFinalized(view.outputView.controller.outputModel, count, 60.seconds)
     val actual = view.outputView.controller.outputModel.collectCommandResults()
     Assert.assertEquals(expected, actual)
   }