Fixes #8690: Do not attempt to sort already sorted lines

src/vs/editor/contrib/linesOperations/common/linesOperations.ts

@@ -111,6 +111,10 @@ class SortLinesAction extends EditorAction {
 
 	public run():TPromise<boolean> {
 
+		if (!SortLinesCommand.canRun(this.editor.getModel(), this.editor.getSelection(), this.descending)) {
+			return TPromise.as(false);
+		}
+
 		var command = new SortLinesCommand(this.editor.getSelection(), this.descending);
 
 		this.editor.executeCommands(this.id, [command]);

src/vs/editor/contrib/linesOperations/common/sortLinesCommand.ts

@@ -32,12 +32,25 @@ export class SortLinesCommand implements editorCommon.ICommand {
 	public computeCursorState(model:editorCommon.ITokenizedModel, helper: editorCommon.ICursorStateComputerData):Selection {
 		return helper.getTrackedSelection(this.selectionId);
 	}
+
+	public static canRun(model:editorCommon.ITextModel, selection:Selection, descending:boolean): boolean {
+		let data = getSortData(model, selection, descending);
+
+		if (!data) {
+			return false;
+		}
+
+		for (let i = 0, len = data.before.length; i < len; i++) {
+			if (data.before[i] !== data.after[i]) {
+				return true;
+			}
+		}
+
+		return false;
+	}
 }
 
-/**
- * Generate commands for sorting lines on a model.
- */
-export function sortLines(model:editorCommon.ITextModel, selection:Selection, descending:boolean): editorCommon.IIdentifiedSingleEditOperation {
+function getSortData(model:editorCommon.ITextModel, selection:Selection, descending:boolean) {
 	let startLineNumber = selection.startLineNumber;
 	let endLineNumber = selection.endLineNumber;
 
@@ -57,7 +70,8 @@ export function sortLines(model:editorCommon.ITextModel, selection:Selection, de
 		linesToSort.push(model.getLineContent(lineNumber));
 	}
 
-	let sorted = linesToSort.sort((a, b) => {
+	let sorted = linesToSort.slice(0);
+	sorted.sort((a, b) => {
 		return a.toLowerCase().localeCompare(b.toLowerCase());
 	});
 
@@ -66,8 +80,26 @@ export function sortLines(model:editorCommon.ITextModel, selection:Selection, de
 		sorted = sorted.reverse();
 	}
 
+	return {
+		startLineNumber: startLineNumber,
+		endLineNumber: endLineNumber,
+		before: linesToSort,
+		after: sorted
+	};
+}
+
+/**
+ * Generate commands for sorting lines on a model.
+ */
+function sortLines(model:editorCommon.ITextModel, selection:Selection, descending:boolean): editorCommon.IIdentifiedSingleEditOperation {
+	let data = getSortData(model, selection, descending);
+
+	if (!data) {
+		return null;
+	}
+
 	return EditOperation.replace(
-		new Range(startLineNumber, 1, endLineNumber, model.getLineMaxColumn(endLineNumber)),
-		sorted.join('\n')
+		new Range(data.startLineNumber, 1, data.endLineNumber, model.getLineMaxColumn(data.endLineNumber)),
+		data.after.join('\n')
 	);
 }