keep old setting as it and add dependent setting

src/vs/workbench/contrib/codeEditor/browser/saveParticipants.ts

@@ -239,19 +239,23 @@ class FormatOnSaveParticipant implements ITextFileSaveParticipant {
 				)
 			});
 		});
-		const editorOrModel = findEditor(textEditorModel, this.codeEditorService) || textEditorModel;
-		const config = this.configurationService.getValue<boolean | string>('editor.formatOnSave', overrides);
 
-		if (config === true || config === 'file') {
-			// format the whole file
-			await this.instantiationService.invokeFunction(formatDocumentWithSelectedProvider, editorOrModel, FormattingMode.Silent, nestedProgress, token);
+		const enabled = this.configurationService.getValue<boolean>('editor.formatOnSave', overrides);
+		if (!enabled) {
+			return undefined;
+		}
 
-		} else if (config === 'modifications') {
+		const editorOrModel = findEditor(textEditorModel, this.codeEditorService) || textEditorModel;
+		const mode = this.configurationService.getValue<'file' | 'modifications'>('editor.formatOnSaveMode', overrides);
+		if (mode === 'modifications') {
 			// format modifications
 			const ranges = await this.instantiationService.invokeFunction(getModifiedRanges, isCodeEditor(editorOrModel) ? editorOrModel.getModel() : editorOrModel);
 			if (ranges) {
 				await this.instantiationService.invokeFunction(formatDocumentRangesWithSelectedProvider, editorOrModel, ranges, FormattingMode.Silent, nestedProgress, token);
 			}
+		} else {
+			// format the whole file
+			await this.instantiationService.invokeFunction(formatDocumentWithSelectedProvider, editorOrModel, FormattingMode.Silent, nestedProgress, token);
 		}
 	}
 }

src/vs/workbench/contrib/files/browser/files.contribution.ts

@@ -360,21 +360,24 @@ configurationRegistry.registerConfiguration({
 	...editorConfigurationBaseNode,
 	properties: {
 		'editor.formatOnSave': {
+			'type': 'boolean',
+			'description': nls.localize('formatOnSave', "Format a file on save. A formatter must be available, the file must not be saved after delay, and the editor must not be shutting down."),
+			'scope': ConfigurationScope.LANGUAGE_OVERRIDABLE,
+		},
+		'editor.formatOnSaveMode': {
 			'type': 'string',
-			'default': 'off',
+			'default': 'file',
 			'enum': [
-				'off',
 				'file',
 				'modifications'
 			],
 			'enumDescriptions': [
-				nls.localize('off', "Disable format on save."),
-				nls.localize('everything', "Format the whole."),
+				nls.localize('everything', "Format the whole file."),
 				nls.localize('modification', "Format modifications (requires source control)."),
 			],
-			'description': nls.localize('formatOnSave', "Format a file on save. A formatter must be available, the file must not be saved after delay, and the editor must not be shutting down."),
-			scope: ConfigurationScope.LANGUAGE_OVERRIDABLE,
-		}
+			'markdownDescription': nls.localize('formatOnSaveMode', "Controls if format on save formats the whole file or only modifications. Only applies when `#editor.formatOnSave#` is `true`."),
+			'scope': ConfigurationScope.LANGUAGE_OVERRIDABLE,
+		},
 	}
 });