Fix nns neuron sorting (#4804)

# Motivation

Fix inconsistency in nns neuron sorting when there are neurons with the
same stake and dissolve delay.

# Changes

- Additionally compare neurons by createdTimestamp.

# Tests

- Tested manually.
- Unit tests extended.

# Todos

- [x] Add entry to changelog (if necessary).

CHANGELOG-Nns-Dapp-unreleased.md

@@ -35,6 +35,7 @@ proposal is successful, the changes it released will be moved from this file to
 
 #### Fixed
 
+* Inconsistency in similar NNS neuron sorting.
 * Adjust Metrics block visibility for certain screen widths.
 
 #### Security

frontend/src/lib/utils/neuron.utils.ts

@@ -299,7 +299,8 @@ export const formatMaturity = (value?: bigint): string =>
 
 // Used to sort neurons by:
 // * decreasing stake, or when stake is equal by
-// * decreasing dissolve delay
+// * decreasing dissolve delay, or when dissolve delay is equal by
+// * decreasing created timestamp
 const compareNeurons = (a: NeuronInfo, b: NeuronInfo): number => {
   const stakeA = neuronStake(a);
   const stakeB = neuronStake(b);
@@ -317,6 +318,14 @@ const compareNeurons = (a: NeuronInfo, b: NeuronInfo): number => {
   if (dissolveDelayA < dissolveDelayB) {
     return 1;
   }
+  const createdTimestampA = a.createdTimestampSeconds;
+  const createdTimestampB = b.createdTimestampSeconds;
+  if (createdTimestampA > createdTimestampB) {
+    return -1;
+  }
+  if (createdTimestampA < createdTimestampB) {
+    return 1;
+  }
   return 0;
 };
 

frontend/src/tests/lib/utils/neuron.utils.spec.ts

@@ -751,6 +751,36 @@ describe("neuron-utils", () => {
         neuron1,
       ]);
     });
+
+    it("should sort neurons by createdTimestamp when stake and dissolve delay are equal", () => {
+      const neuronA = {
+        ...mockNeuron,
+        dissolveDelaySeconds: 200_000_000n,
+        createdTimestampSeconds: 1n,
+      };
+      const neuronB = {
+        ...mockNeuron,
+        dissolveDelaySeconds: 100_000_000n,
+        createdTimestampSeconds: 3n,
+      };
+      const neuronC = {
+        ...mockNeuron,
+        dissolveDelaySeconds: 100_000_000n,
+        createdTimestampSeconds: 2n,
+      };
+      expect(sortNeuronsByStake([])).toEqual([]);
+      expect(sortNeuronsByStake([neuronA])).toEqual([neuronA]);
+      expect(sortNeuronsByStake([neuronB, neuronC, neuronA])).toEqual([
+        neuronA,
+        neuronB,
+        neuronC,
+      ]);
+      expect(sortNeuronsByStake([neuronA, neuronB, neuronC])).toEqual([
+        neuronA,
+        neuronB,
+        neuronC,
+      ]);
+    });
   });
 
   describe("isNeuronControllable", () => {