GIX-1890: Check transaction fee disburse maturity (#3331)

# Motivation

Users can't disburse maturity if less than transaction fee.

It's just used as a minimum, it's not that a fee is applied to the
amount.

# Changes

* A new prop `disabledText` in NeuronSelectPercentage.
* New prop in DisburseMaturityModal. Check to enable or disable first
screen.
* New neuron util `minimumAmountToDisburseMaturity`.
* Rename `SPAWN_VARIANCE_PERCENTAGE` to
`MATURITY_MODULATION_VARIANCE_PERCENTAGE`.

# Tests

* Add test case in SnsDisburseMaturityModal.spec.
* Add test for new neuron util.

# Todos

- [ ] Add entry to changelog (if necessary).
Already covered by disburse maturity entry.

frontend/src/lib/components/neuron-detail/NeuronSelectPercentage.svelte

@@ -6,11 +6,14 @@
   import TestIdWrapper from "$lib/components/common/TestIdWrapper.svelte";
   import { formatMaturity } from "$lib/utils/neuron.utils";
   import { replacePlaceholders } from "$lib/utils/i18n.utils";
+  import { nonNullish } from "@dfinity/utils";
+  import Tooltip from "../ui/Tooltip.svelte";
 
   export let availableMaturityE8s: bigint;
   export let percentage: number;
   export let buttonText: string;
   export let disabled = false;
+  export let disabledText: string | undefined = undefined;
 
   let selectedMaturityE8s: bigint;
   $: selectedMaturityE8s = (availableMaturityE8s * BigInt(percentage)) / 100n;
@@ -59,14 +62,27 @@
     <button class="secondary" on:click={() => dispatcher("nnsCancel")}>
       {$i18n.core.cancel}
     </button>
-    <button
-      data-tid="select-maturity-percentage-button"
-      class="primary"
-      on:click={selectPercentage}
-      {disabled}
-    >
-      {buttonText}
-    </button>
+    {#if nonNullish(disabledText)}
+      <Tooltip id="disabled-disburse-button-modal" text={disabledText}>
+        <button
+          data-tid="select-maturity-percentage-button"
+          class="primary"
+          on:click={selectPercentage}
+          {disabled}
+        >
+          {buttonText}
+        </button>
+      </Tooltip>
+    {:else}
+      <button
+        data-tid="select-maturity-percentage-button"
+        class="primary"
+        on:click={selectPercentage}
+        {disabled}
+      >
+        {buttonText}
+      </button>
+    {/if}
   </div>
 </TestIdWrapper>
 

frontend/src/lib/components/neuron-detail/actions/SpawnNeuronButton.svelte

@@ -3,7 +3,7 @@
   import { E8S_PER_ICP } from "$lib/constants/icp.constants";
   import {
     MIN_NEURON_STAKE,
-    SPAWN_VARIANCE_PERCENTAGE,
+    MATURITY_MODULATION_VARIANCE_PERCENTAGE,
   } from "$lib/constants/neurons.constants";
   import { i18n } from "$lib/stores/i18n";
   import { formatNumber, formatPercentage } from "$lib/utils/format.utils";
@@ -49,17 +49,22 @@
         $i18n.neuron_detail.spawn_neuron_disabled_tooltip,
         {
           $amount: formatNumber(
-            MIN_NEURON_STAKE / E8S_PER_ICP / SPAWN_VARIANCE_PERCENTAGE,
+            MIN_NEURON_STAKE /
+              E8S_PER_ICP /
+              MATURITY_MODULATION_VARIANCE_PERCENTAGE,
             { minFraction: 4, maxFraction: 4 }
           ),
           $min: formatNumber(MIN_NEURON_STAKE / E8S_PER_ICP, {
             minFraction: 0,
             maxFraction: 0,
           }),
-          $varibility: formatPercentage(SPAWN_VARIANCE_PERCENTAGE, {
-            minFraction: 0,
-            maxFraction: 0,
-          }),
+          $variability: formatPercentage(
+            MATURITY_MODULATION_VARIANCE_PERCENTAGE,
+            {
+              minFraction: 0,
+              maxFraction: 0,
+            }
+          ),
         }
       )}
     >

frontend/src/lib/components/sns-neuron-detail/actions/SnsDisburseMaturityButton.svelte

@@ -1,5 +1,8 @@
 <script lang="ts">
-  import { hasEnoughMaturityToDisburse } from "$lib/utils/sns-neuron.utils";
+  import {
+    hasEnoughMaturityToDisburse,
+    minimumAmountToDisburseMaturity,
+  } from "$lib/utils/sns-neuron.utils";
   import { openSnsNeuronModal } from "$lib/utils/modals.utils";
   import type { SnsNeuron } from "@dfinity/sns";
   import DisburseMaturityButton from "$lib/components/neuron-detail/actions/DisburseMaturityButton.svelte";
@@ -17,7 +20,11 @@
   $: disabledText = !enoughMaturity
     ? replacePlaceholders(
         $i18n.neuron_detail.disburse_maturity_disabled_tooltip,
-        { $fee: formatToken({ value: feeE8s }) }
+        {
+          $amount: formatToken({
+            value: minimumAmountToDisburseMaturity(feeE8s),
+          }),
+        }
       )
     : undefined;
 

frontend/src/lib/constants/neurons.constants.ts

@@ -6,7 +6,7 @@ import { E8S_PER_ICP } from "./icp.constants";
 export const MAX_NEURONS_MERGED = 2;
 export const MIN_NEURON_STAKE = E8S_PER_ICP;
 export const MAX_CONCURRENCY = 10;
-export const SPAWN_VARIANCE_PERCENTAGE = 0.95;
+export const MATURITY_MODULATION_VARIANCE_PERCENTAGE = 0.95;
 // Neuron ids are random u64. Max digits of a u64 is 20.
 export const MAX_NEURON_ID_DIGITS = 20;
 

frontend/src/lib/i18n/en.json

@@ -611,7 +611,7 @@
     "spawn_neuron": "Spawn Neuron",
     "spawn": "Spawn",
     "stake_maturity_disabled_tooltip": "Currently, you do not have any maturity available to stake into this neuron.",
-    "disburse_maturity_disabled_tooltip": "You do not have enough maturity to disburse. The minimum is: $fee.",
+    "disburse_maturity_disabled_tooltip": "You do not have enough maturity to disburse. The minimum is: $amount.",
     "stake_maturity_tooltip": "Merge Maturity has been replaced by Stake Maturity. <a href=\"https://wiki.internetcomputer.org/wiki/NNS_neuron_operations_related_to_maturity\" rel=\"noopener noreferrer\" aria-label=\"Find more information about the new stake maturity\" target=\"_blank\">Learn more</a>.",
     "start_dissolve_description": "This will cause your neuron to lose its age bonus.\nAre you sure you wish to continue?",
     "stop_dissolve_description": "Are you sure you want to stop the dissolve process?",
@@ -628,7 +628,7 @@
     "disburse_neuron_title": "Disburse Neuron",
     "split_neuron_success": "Your neuron has successfully been split.",
     "split_neuron_disabled_tooltip": "Neuron needs a minimum stake of $amount $token to be splittable.",
-    "spawn_neuron_disabled_tooltip": "You need at least the equivalent of $amount ICP ($min / $varibility) to spawn a new neuron from maturity.",
+    "spawn_neuron_disabled_tooltip": "You need at least the equivalent of $amount ICP ($min / $variability) to spawn a new neuron from maturity.",
     "hotkeys_title": "Hotkeys",
     "add_hotkey": "Add Hotkey",
     "no_notkeys": "No hotkeys",

frontend/src/lib/modals/neurons/DisburseMaturityModal.svelte

@@ -18,6 +18,8 @@
   export let availableMaturityE8s: bigint;
   export let tokenSymbol: string;
 
+  export let minimumAmountE8s: bigint;
+
   const steps: WizardSteps = [
     {
       name: "SelectPercentage",
@@ -33,6 +35,22 @@
   let modal: WizardModal;
 
   let percentageToDisburse = 0;
+  let selectedMaturityE8s: bigint;
+  $: selectedMaturityE8s =
+    (availableMaturityE8s * BigInt(percentageToDisburse)) / 100n;
+
+  let disableDisburse = false;
+  $: disableDisburse = selectedMaturityE8s < minimumAmountE8s;
+
+  // Show the text only if the selected percentage is greater than 0.
+  let disabledText: string | undefined = undefined;
+  $: disabledText =
+    disableDisburse && percentageToDisburse > 0
+      ? replacePlaceholders(
+          $i18n.neuron_detail.disburse_maturity_disabled_tooltip,
+          { $amount: formatToken({ value: minimumAmountE8s }) }
+        )
+      : undefined;
 
   const dispatcher = createEventDispatcher();
   const disburseNeuronMaturity = () =>
@@ -74,7 +92,8 @@
       on:nnsSelectPercentage={goToConfirm}
       on:nnsCancel={close}
       bind:percentage={percentageToDisburse}
-      disabled={percentageToDisburse === 0}
+      disabled={disableDisburse}
+      {disabledText}
     >
       <div class="percentage-container" slot="description">
         <span class="description">

frontend/src/lib/modals/sns/neurons/SnsDisburseMaturityModal.svelte

@@ -5,12 +5,15 @@
   import type { SnsNeuron, SnsNeuronId } from "@dfinity/sns";
   import type { Principal } from "@dfinity/principal";
   import { disburseMaturity as disburseMaturityService } from "$lib/services/sns-neurons.services";
-  import { formattedMaturity } from "$lib/utils/sns-neuron.utils";
+  import {
+    formattedMaturity,
+    minimumAmountToDisburseMaturity,
+  } from "$lib/utils/sns-neuron.utils";
   import DisburseMaturityModal from "$lib/modals/neurons/DisburseMaturityModal.svelte";
   import { snsProjectMainAccountStore } from "$lib/derived/sns/sns-project-accounts.derived";
   import { shortenWithMiddleEllipsis } from "$lib/utils/format.utils";
   import { tokensStore } from "$lib/stores/tokens.store";
-  import type { Token } from "@dfinity/utils";
+  import type { IcrcTokenMetadata } from "$lib/types/icrc";
 
   export let neuron: SnsNeuron;
   export let neuronId: SnsNeuronId;
@@ -25,9 +28,14 @@
     $snsProjectMainAccountStore?.identifier ?? ""
   );
 
-  let token: Token | undefined;
+  let token: IcrcTokenMetadata | undefined;
   $: token = $tokensStore[rootCanisterId.toText()]?.token;
 
+  let minimumAmountE8s: bigint;
+  // Token is loaded with all the projects from the aggregator.
+  // Therefore, if the user made it here, it's present.
+  $: minimumAmountE8s = minimumAmountToDisburseMaturity(token?.fee ?? 0n);
+
   const dispatcher = createEventDispatcher();
   const close = () => dispatcher("nnsClose");
 
@@ -57,6 +65,7 @@
 
 <DisburseMaturityModal
   availableMaturityE8s={neuron.maturity_e8s_equivalent}
+  {minimumAmountE8s}
   tokenSymbol={token?.symbol ?? ""}
   on:nnsDisburseMaturity={disburseMaturity}
   on:nnsClose

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

@@ -12,9 +12,9 @@ import {
 import {
   AGE_MULTIPLIER,
   DISSOLVE_DELAY_MULTIPLIER,
+  MATURITY_MODULATION_VARIANCE_PERCENTAGE,
   MAX_NEURONS_MERGED,
   MIN_NEURON_STAKE,
-  SPAWN_VARIANCE_PERCENTAGE,
   TOPICS_TO_FOLLOW_NNS,
 } from "$lib/constants/neurons.constants";
 import { DEPRECATED_TOPICS } from "$lib/constants/proposals.constants";
@@ -499,7 +499,10 @@ export const isEnoughMaturityToSpawn = ({
   const maturitySelected = Math.floor(
     (Number(fullNeuron.maturityE8sEquivalent) * percentage) / 100
   );
-  return maturitySelected >= MIN_NEURON_STAKE / SPAWN_VARIANCE_PERCENTAGE;
+  return (
+    maturitySelected >=
+    MIN_NEURON_STAKE / MATURITY_MODULATION_VARIANCE_PERCENTAGE
+  );
 };
 
 export const isSpawning = (neuron: NeuronInfo): boolean =>

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

@@ -1,3 +1,4 @@
+import { MATURITY_MODULATION_VARIANCE_PERCENTAGE } from "$lib/constants/neurons.constants";
 import {
   HOTKEY_PERMISSIONS,
   MANAGE_HOTKEY_PERMISSIONS,
@@ -505,7 +506,7 @@ export const hasEnoughMaturityToStake = (
 ): boolean => (neuron?.maturity_e8s_equivalent ?? BigInt(0)) > BigInt(0);
 
 /**
- * Is the maturity of the neuron bigger than the transaction fee?
+ * Is the maturity of the neuron bigger than the minimum amount to disburse?
  * @param {SnsNeuron} neuron
  * @param {bigint} feeE8s
  */
@@ -515,7 +516,8 @@ export const hasEnoughMaturityToDisburse = ({
 }: {
   feeE8s: bigint;
   neuron: SnsNeuron;
-}): boolean => maturity_e8s_equivalent >= feeE8s;
+}): boolean =>
+  maturity_e8s_equivalent >= minimumAmountToDisburseMaturity(feeE8s);
 
 /**
  * Does the neuron has staked maturity?
@@ -981,3 +983,11 @@ export const totalDisbursingMaturity = ({
     (acc, disbursement) => acc + disbursement.amount_e8s,
     BigInt(0)
   );
+
+/**
+ * The governance canister checks that the amount to disburse in the worst case (of the maturity modulation) is bigger than the transaction fee.
+ *
+ * Source: https://sourcegraph.com/github.com/dfinity/ic/-/blob/rs/sns/governance/src/governance.rs?L1651
+ */
+export const minimumAmountToDisburseMaturity = (fee: bigint): bigint =>
+  BigInt(Math.ceil(Number(fee) / MATURITY_MODULATION_VARIANCE_PERCENTAGE));

frontend/src/tests/lib/components/sns-neuron-detail/actions/SnsDisburseMaturityButton.spec.ts

@@ -29,7 +29,7 @@ describe("SnsDisburseMaturityButton", () => {
     const po = renderComponent(
       {
         ...mockSnsNeuron,
-        maturity_e8s_equivalent: fee + 10n,
+        maturity_e8s_equivalent: fee * 2n,
         staked_maturity_e8s_equivalent: [],
       },
       fee
@@ -50,7 +50,7 @@ describe("SnsDisburseMaturityButton", () => {
 
     expect(await po.isDisabled()).toBe(true);
     expect(await po.getTooltipText()).toBe(
-      "You do not have enough maturity to disburse. The minimum is: 0.0001."
+      "You do not have enough maturity to disburse. The minimum is: 0.00010527."
     );
   });
 

frontend/src/tests/lib/modals/sns/SnsDisburseMaturityModal.spec.ts

@@ -65,6 +65,26 @@ describe("SnsDisburseMaturityModal", () => {
     expect(await po.isNextButtonDisabled()).toBe(false);
   });
 
+  it("should disable next button if amount of maturity is less than transaction fee", async () => {
+    const fee = 100_000_000n;
+    const neuron = createMockSnsNeuron({
+      id: [1],
+      maturity: fee * 2n,
+    });
+    tokensStore.setToken({
+      canisterId: rootCanisterId,
+      token: {
+        fee,
+        ...mockSnsToken,
+      },
+    });
+    // Maturity is 2x the fee, so 10% of maturity is not enough to cover the fee
+    const percentage = 10;
+    const po = await renderSnsDisburseMaturityModal(neuron);
+    await po.setPercentage(percentage);
+    expect(await po.isNextButtonDisabled()).toBe(false);
+  });
+
   it("should display selected percentage and total maturity", async () => {
     const neuron = createMockSnsNeuron({
       id: [1],

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

@@ -47,6 +47,7 @@ import {
   isUserHotkey,
   isVesting,
   minNeuronSplittable,
+  minimumAmountToDisburseMaturity,
   needsRefresh,
   neuronAge,
   nextMemo,
@@ -1391,10 +1392,10 @@ describe("sns-neuron utils", () => {
 
   describe("hasEnoughMaturityToDisburse", () => {
     const feeE8s = 10_000n;
-    it("should return true if maturity is more than fee", () => {
+    it("should return true if maturity is more than fee in worst modulation scenario", () => {
       const neuron = {
         ...mockSnsNeuron,
-        maturity_e8s_equivalent: feeE8s + 1n,
+        maturity_e8s_equivalent: 10526n + 1n,
       };
       expect(hasEnoughMaturityToDisburse({ neuron, feeE8s })).toBe(true);
     });
@@ -1407,12 +1408,12 @@ describe("sns-neuron utils", () => {
       expect(hasEnoughMaturityToDisburse({ neuron, feeE8s })).toBe(false);
     });
 
-    it("should return true if maturity is same as fee", () => {
+    it("should return false if maturity is same as fee", () => {
       const neuron = {
         ...mockSnsNeuron,
         maturity_e8s_equivalent: feeE8s,
       };
-      expect(hasEnoughMaturityToDisburse({ neuron, feeE8s })).toBe(true);
+      expect(hasEnoughMaturityToDisburse({ neuron, feeE8s })).toBe(false);
     });
   });
 
@@ -2492,4 +2493,14 @@ describe("sns-neuron utils", () => {
       expect(totalDisbursingMaturity(neuron)).toBe(0n);
     });
   });
+
+  describe("minimumAmountToDisburseMaturity", () => {
+    it("returns worst case of maturity modulation", () => {
+      expect(minimumAmountToDisburseMaturity(10_000n)).toBe(10527n);
+    });
+
+    it("returns 0 if fee is 0", () => {
+      expect(minimumAmountToDisburseMaturity(0n)).toBe(0n);
+    });
+  });
 });