From 69fd7afc56b4c4f793981d6b0cfbeb06cc1ae613 Mon Sep 17 00:00:00 2001
From: Benjamin Pasero <benjpas@microsoft.com>
Date: Thu, 16 Jul 2020 10:50:52 +0200
Subject: [PATCH] throttle save participants in certain cases (#102542)

---
 .../textfile/common/textFileEditorModel.ts    | 40 +++++++++++++++++--
 1 file changed, 37 insertions(+), 3 deletions(-)

diff --git a/src/vs/workbench/services/textfile/common/textFileEditorModel.ts b/src/vs/workbench/services/textfile/common/textFileEditorModel.ts
index b0a885ddd0657..1bb7ac6975d25 100644
--- a/src/vs/workbench/services/textfile/common/textFileEditorModel.ts
+++ b/src/vs/workbench/services/textfile/common/textFileEditorModel.ts
@@ -75,6 +75,9 @@ export class TextFileEditorModel extends BaseTextEditorModel implements ITextFil
 	private bufferSavedVersionId: number | undefined;
 	private ignoreDirtyOnModelContentChange = false;
 
+	private static readonly UNDO_REDO_SAVE_PARTICIPANTS_AUTO_SAVE_THROTTLE_THRESHOLD = 500;
+	private lastModelContentChangeFromUndoRedo: number | undefined = undefined;
+
 	private lastResolvedFileStat: IFileStatWithMetadata | undefined;
 
 	private readonly saveSequentializer = new TaskSequentializer();
@@ -450,16 +453,23 @@ export class TextFileEditorModel extends BaseTextEditorModel implements ITextFil
 		// where `value` was captured in the content change listener closure scope.
 
 		// Content Change
-		this._register(model.onDidChangeContent(() => this.onModelContentChanged(model)));
+		this._register(model.onDidChangeContent(e => this.onModelContentChanged(model, e.isUndoing || e.isRedoing)));
 	}
 
-	private onModelContentChanged(model: ITextModel): void {
+	private onModelContentChanged(model: ITextModel, isUndoingOrRedoing: boolean): void {
 		this.logService.trace(`[text file model] onModelContentChanged() - enter`, this.resource.toString(true));
 
 		// In any case increment the version id because it tracks the textual content state of the model at all times
 		this.versionId++;
 		this.logService.trace(`[text file model] onModelContentChanged() - new versionId ${this.versionId}`, this.resource.toString(true));
 
+		// Remember when the user changed the model through a undo/redo operation.
+		// We need this information to throttle save participants to fix
+		// https://github.com/microsoft/vscode/issues/102542
+		if (isUndoingOrRedoing) {
+			this.lastModelContentChangeFromUndoRedo = Date.now();
+		}
+
 		// We mark check for a dirty-state change upon model content change, unless:
 		// - explicitly instructed to ignore it (e.g. from model.load())
 		// - the model is readonly (in that case we never assume the change was done by the user)
@@ -639,7 +649,31 @@ export class TextFileEditorModel extends BaseTextEditorModel implements ITextFil
 			// Save participants can also be skipped through API.
 			if (this.isResolved() && !options.skipSaveParticipants) {
 				try {
-					await this.textFileService.files.runSaveParticipants(this, { reason: options.reason ?? SaveReason.EXPLICIT }, saveCancellation.token);
+
+					// Measure the time it took from the last undo/redo operation to this save. If this
+					// time is below `UNDO_REDO_SAVE_PARTICIPANTS_THROTTLE_THRESHOLD`, we make sure to
+					// delay the save participant for the remaining time if the reason is auto save.
+					//
+					// This fixes the following issue:
+					// - the user has configured auto save with delay of 100ms or shorter
+					// - the user has a save participant enabled that modifies the file on each save
+					// - the user types into the file and the file gets saved
+					// - the user triggers undo operation
+					// - this will undo the save participant change but trigger the save participant right after
+					// - the user has no chance to undo over the save participant
+					//
+					// Reported as: https://github.com/microsoft/vscode/issues/102542
+					if (options.reason === SaveReason.AUTO && typeof this.lastModelContentChangeFromUndoRedo === 'number') {
+						const timeFromUndoRedoToSave = Date.now() - this.lastModelContentChangeFromUndoRedo;
+						if (timeFromUndoRedoToSave < TextFileEditorModel.UNDO_REDO_SAVE_PARTICIPANTS_AUTO_SAVE_THROTTLE_THRESHOLD) {
+							await timeout(TextFileEditorModel.UNDO_REDO_SAVE_PARTICIPANTS_AUTO_SAVE_THROTTLE_THRESHOLD - timeFromUndoRedoToSave);
+						}
+					}
+
+					// Run save participants unless save was cancelled meanwhile
+					if (!saveCancellation.token.isCancellationRequested) {
+						await this.textFileService.files.runSaveParticipants(this, { reason: options.reason ?? SaveReason.EXPLICIT }, saveCancellation.token);
+					}
 				} catch (error) {
 					this.logService.error(`[text file model] runSaveParticipants(${versionId}) - resulted in an error: ${error.toString()}`, this.resource.toString(true));
 				}