Return 0 from sortFunc when values are equal

web/src/utils/common.test.ts

@@ -0,0 +1,67 @@
+import { sortFunc, sortDateFunc } from "./common";
+
+test("sortFunc orders values in the requested direction", () => {
+  expect(sortFunc("a", "b")).toBe(-1);
+  expect(sortFunc("b", "a")).toBe(1);
+  expect(sortFunc(1, 2)).toBe(-1);
+  expect(sortFunc(2, 1)).toBe(1);
+
+  expect(sortFunc("a", "b", "DESC")).toBe(1);
+  expect(sortFunc("b", "a", "DESC")).toBe(-1);
+});
+
+test("sortFunc returns 0 for equal values", () => {
+  expect(sortFunc("a", "a")).toBe(0);
+  expect(sortFunc(1, 1)).toBe(0);
+  expect(sortFunc("a", "a", "DESC")).toBe(0);
+  expect(sortFunc(1, 1, "DESC")).toBe(0);
+});
+
+test("sortFunc keeps equal elements in their original order", () => {
+  // Array.prototype.sort is only stable when the comparator returns 0 for
+  // equal elements. Applications and pipeds can share a name, so this is the
+  // ordering users actually see in the application forms.
+  const items = [
+    { name: "api", id: 1 },
+    { name: "api", id: 2 },
+    { name: "api", id: 3 },
+    { name: "api", id: 4 },
+    { name: "api", id: 5 },
+    { name: "api", id: 6 },
+    { name: "web", id: 7 },
+    { name: "api", id: 8 },
+    { name: "api", id: 9 },
+    { name: "api", id: 10 },
+    { name: "api", id: 11 },
+    { name: "api", id: 12 },
+  ];
+
+  const sorted = [...items].sort((a, b) => sortFunc(a.name, b.name));
+
+  expect(sorted.map((item) => item.id)).toEqual([
+    1,
+    2,
+    3,
+    4,
+    5,
+    6,
+    8,
+    9,
+    10,
+    11,
+    12,
+    7,
+  ]);
+});
+
+test("sortDateFunc orders dates in the requested direction", () => {
+  expect(sortDateFunc("2024-01-01", "2024-01-02")).toBe(-1);
+  expect(sortDateFunc("2024-01-02", "2024-01-01")).toBe(1);
+  expect(sortDateFunc("2024-01-01", "2024-01-02", "DESC")).toBe(1);
+  expect(sortDateFunc("2024-01-02", "2024-01-01", "DESC")).toBe(-1);
+});
+
+test("sortDateFunc returns 0 for equal dates", () => {
+  expect(sortDateFunc("2024/01/01", "2024/01/01")).toBe(0);
+  expect(sortDateFunc("2024/01/01", "2024/01/01", "DESC")).toBe(0);
+});

web/src/utils/common.ts

@@ -7,6 +7,7 @@ export const sortFunc = (
   b: string | number,
   direction: "ASC" | "DESC" = "ASC"
 ): number => {
+  if (a === b) return 0;
   if (direction === "ASC") return a > b ? 1 : -1;
   return a > b ? -1 : 1;
 };