Investigate to cancel a running save participant when saving again

src/vs/workbench/api/browser/mainThreadSaveParticipant.ts

@@ -365,9 +365,9 @@ export class SaveParticipant implements ISaveParticipant {
 		this._saveParticipants.dispose();
 	}
 
-	async participate(model: IResolvedTextFileEditorModel, env: { reason: SaveReason; }): Promise<void> {
+	async participate(model: IResolvedTextFileEditorModel, context: { reason: SaveReason; }, token: CancellationToken): Promise<void> {
 
-		const cts = new CancellationTokenSource();
+		const cts = new CancellationTokenSource(token);
 
 		return this._progressService.withProgress({
 			title: localize('saveParticipants', "Running Save Participants for '{0}'", this._labelService.getUriLabel(model.resource, { relative: true })),
@@ -383,7 +383,7 @@ export class SaveParticipant implements ISaveParticipant {
 					break;
 				}
 				try {
-					const promise = p.participate(model, env, progress, cts.token);
+					const promise = p.participate(model, context, progress, cts.token);
 					await raceCancellation(promise, cts.token);
 				} catch (err) {
 					this._logService.warn(err);

src/vs/workbench/services/textfile/common/saveSequenzializer.ts

@@ -5,6 +5,7 @@
 
 interface IPendingSave {
 	versionId: number;
+	cancel: () => void;
 	promise: Promise<void>;
 }
 
@@ -35,8 +36,12 @@ export class SaveSequentializer {
 		return this._pendingSave ? this._pendingSave.promise : undefined;
 	}
 
-	setPending(versionId: number, promise: Promise<void>): Promise<void> {
-		this._pendingSave = { versionId, promise };
+	cancelPending(): void {
+		this._pendingSave?.cancel();
+	}
+
+	setPending(versionId: number, promise: Promise<void>, onCancel?: () => void, ): Promise<void> {
+		this._pendingSave = { versionId, cancel: () => onCancel?.(), promise };
 
 		promise.then(() => this.donePending(versionId), () => this.donePending(versionId));
 

src/vs/workbench/services/textfile/common/textFileEditorModel.ts

@@ -24,6 +24,7 @@ import { IWorkingCopyService, IWorkingCopyBackup } from 'vs/workbench/services/w
 import { IFilesConfigurationService } from 'vs/workbench/services/filesConfiguration/common/filesConfigurationService';
 import { SaveSequentializer } from 'vs/workbench/services/textfile/common/saveSequenzializer';
 import { ILabelService } from 'vs/platform/label/common/label';
+import { CancellationTokenSource } from 'vs/base/common/cancellation';
 
 interface IBackupMetaData {
 	mtime: number;
@@ -601,6 +602,13 @@ export class TextFileEditorModel extends BaseTextEditorModel implements ITextFil
 		if (this.saveSequentializer.hasPendingSave()) {
 			this.logService.trace(`[text file model] doSave(${versionId}) - exit - because busy saving`, this.resource.toString());
 
+			// Indicate to the save sequentializer that we want to
+			// cancel the pending operation so that ours can run
+			// before the pending one finishes.
+			// Currently this will try to cancel pending save
+			// participants but never a pending save.
+			this.saveSequentializer.cancelPending();
+
 			// Register this as the next upcoming save and return
 			return this.saveSequentializer.setNext(() => this.doSave(options));
 		}
@@ -616,6 +624,7 @@ export class TextFileEditorModel extends BaseTextEditorModel implements ITextFil
 		// In addition we update our version right after in case it changed because of a model change
 		//
 		// Save participants can also be skipped through API.
+		const saveParticipantCancellation = new CancellationTokenSource();
 		let saveParticipantPromise: Promise<number> = Promise.resolve(versionId);
 		if (this.isResolved() && this.textFileService.saveParticipant && !options.skipSaveParticipants) {
 			const onCompleteOrError = () => {
@@ -625,7 +634,7 @@ export class TextFileEditorModel extends BaseTextEditorModel implements ITextFil
 			};
 
 			this.ignoreDirtyOnModelContentChange = true;
-			saveParticipantPromise = this.textFileService.saveParticipant.participate(this, { reason: options.reason }).then(onCompleteOrError, onCompleteOrError);
+			saveParticipantPromise = this.textFileService.saveParticipant.participate(this, { reason: options.reason }, saveParticipantCancellation.token).then(onCompleteOrError, onCompleteOrError);
 		}
 
 		// mark the save participant as current pending save operation
@@ -678,7 +687,7 @@ export class TextFileEditorModel extends BaseTextEditorModel implements ITextFil
 				etag: (options.ignoreModifiedSince || !this.filesConfigurationService.preventSaveConflicts(lastResolvedFileStat.resource, this.getMode())) ? ETAG_DISABLED : lastResolvedFileStat.etag,
 				writeElevated: options.writeElevated
 			}).then(stat => this.handleSaveSuccess(stat, versionId, options), error => this.handleSaveError(error, versionId, options)));
-		}));
+		}), () => saveParticipantCancellation.cancel());
 	}
 
 	private handleSaveSuccess(stat: IFileStatWithMetadata, versionId: number, options: ITextFileSaveOptions): void {

src/vs/workbench/services/textfile/common/textfiles.ts

@@ -16,6 +16,7 @@ import { isUndefinedOrNull } from 'vs/base/common/types';
 import { isNative } from 'vs/base/common/platform';
 import { IWorkingCopy } from 'vs/workbench/services/workingCopy/common/workingCopyService';
 import { IUntitledTextEditorModelManager } from 'vs/workbench/services/untitled/common/untitledTextEditorService';
+import { CancellationToken } from 'vs/base/common/cancellation';
 
 export const ITextFileService = createDecorator<ITextFileService>('textFileService');
 
@@ -230,7 +231,7 @@ export interface ISaveParticipant {
 	/**
 	 * Participate in a save of a model. Allows to change the model before it is being saved to disk.
 	 */
-	participate(model: IResolvedTextFileEditorModel, env: { reason: SaveReason }): Promise<void>;
+	participate(model: IResolvedTextFileEditorModel, context: { reason: SaveReason }, token: CancellationToken): Promise<void>;
 }
 
 /**

src/vs/workbench/services/textfile/test/browser/textFileEditorModel.test.ts

@@ -556,4 +556,34 @@ suite('Files - TextFileEditorModel', () => {
 		await model.save();
 		model.dispose();
 	});
+
+	test('Save Participant, participant cancelled when saved again', async function () {
+		const model: TextFileEditorModel = instantiationService.createInstance(TextFileEditorModel, toResource.call(this, '/path/index_async.txt'), 'utf8', undefined);
+
+		let participations: boolean[] = [];
+
+		accessor.textFileService.saveParticipant = {
+			participate: (model) => {
+				return timeout(10).then(() => {
+					participations.push(true);
+				});
+			}
+		};
+
+		await model.load();
+
+		model.textEditorModel!.setValue('foo');
+		const p1 = model.save();
+
+		model.textEditorModel!.setValue('foo 1');
+		const p2 = model.save();
+
+		model.textEditorModel!.setValue('foo 2');
+		await model.save();
+
+		await p1;
+		await p2;
+		assert.equal(participations.length, 1);
+		model.dispose();
+	});
 });

src/vs/workbench/services/textfile/test/common/saveSequenzializer.test.ts

@@ -87,4 +87,14 @@ suite('Files - SaveSequentializer', () => {
 		assert.ok(!secondDone);
 		assert.ok(thirdDone);
 	});
+
+	test('SaveSequentializer - cancel pending', async function () {
+		const sequentializer = new SaveSequentializer();
+
+		let pendingCancelled = false;
+		sequentializer.setPending(1, timeout(1), () => pendingCancelled = true);
+		sequentializer.cancelPending();
+
+		assert.ok(pendingCancelled);
+	});
 });