Merge pull request #46227 from AiryShift/bug46075

Fixes #46075

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

@@ -166,7 +166,7 @@ export class TrimFinalNewLinesParticipant implements ISaveParticipantParticipant
 			currentLineIsEmptyOrWhitespace = strings.lastNonWhitespaceIndex(currentLine) === -1;
 		}
 
-		const deletionRange = new Range(currentLineNumber + 1, 1, lineCount + 1, 1);
+		const deletionRange = model.validateRange(new Range(currentLineNumber + 1, 1, lineCount + 1, 1));
 		if (!deletionRange.isEmpty()) {
 			model.pushEditOperations(prevSelection, [EditOperation.delete(deletionRange)], edits => prevSelection);
 		}

src/vs/workbench/test/electron-browser/api/mainThreadSaveParticipant.test.ts

@@ -139,4 +139,31 @@ suite('MainThreadSaveParticipant', function () {
 		});
 	});
 
+	test('trim final new lines bug#46075', function () {
+		const model: TextFileEditorModel = instantiationService.createInstance(TextFileEditorModel, toResource.call(this, '/path/trim_final_new_line.txt'), 'utf8');
+
+		return model.load().then(() => {
+			const configService = new TestConfigurationService();
+			configService.setUserConfiguration('files', { 'trimFinalNewlines': true });
+
+			const participant = new TrimFinalNewLinesParticipant(configService, undefined);
+
+			const textContent = 'Test';
+			const eol = `${model.textEditorModel.getEOL()}`;
+
+			let content = `${textContent}${eol}${eol}`;
+			model.textEditorModel.setValue(content);
+			// save many times
+			for (let i = 0; i < 10; i++) {
+				participant.participate(model, { reason: SaveReason.EXPLICIT });
+			}
+			// confirm trimming
+			assert.equal(snapshotToString(model.createSnapshot()), `${textContent}${eol}`);
+			// undo should go back to previous content immediately
+			model.textEditorModel.undo();
+			assert.equal(snapshotToString(model.createSnapshot()), `${textContent}${eol}${eol}`);
+			model.textEditorModel.redo();
+			assert.equal(snapshotToString(model.createSnapshot()), `${textContent}${eol}`);
+		});
+	});
 });