fix: preserve negative sign when editing an expense

src/components/AddExpense/AddExpensePage.tsx

@@ -172,16 +172,14 @@ export const AddOrEditExpensePage: React.FC<{
                   navPromise = async () => router.back();
                 }
 
+                navPromise().catch(console.error);
                 update((session: any) => ({
                   ...session,
                   user: {
                     ...(session?.user ?? {}),
                     currency,
                   },
-                }))
-                  .then(() => navPromise())
-                  .then(() => resetState())
-                  .catch(console.error);
+                })).catch(console.error);
               }
             }
           },
@@ -206,7 +204,6 @@ export const AddOrEditExpensePage: React.FC<{
     expenseDate,
     expenseId,
     router,
-    resetState,
     addExpenseMutation,
     group,
     paidBy,

src/components/Expense/ConvertibleBalance.tsx

@@ -160,8 +160,6 @@ export const ConvertibleBalance: React.FC<ConvertibleBalanceProps> = ({
     return total;
   }, [shouldShowAll, balances, ratesQuery, selectedCurrency, t, setSelectedCurrency]);
 
-  console.log(selectedCurrency, groupDefaultCurrency);
-
   if (0 === balances.length) {
     return <AmountDisplay className={className} amount={0n} currency="USD" />;
   }

src/components/ui/currency-input.tsx

@@ -21,7 +21,7 @@ const CurrencyInput: React.FC<
       className={cn('text-lg placeholder:text-sm', className)}
       inputMode="decimal"
       value={strValue}
-      onFocus={() => onValueChange({ strValue: parseToCleanString(strValue) })}
+      onFocus={() => onValueChange({ strValue: parseToCleanString(strValue, allowNegative) })}
       onBlur={() => {
         const formattedValue = format(strValue, { signed: allowNegative, hideSymbol });
         return onValueChange({ strValue: formattedValue });

src/pages/add.tsx

@@ -44,7 +44,15 @@ const AddPage: NextPageWithUser<{
   const initializedFriendIdRef = useRef<number | null>(null);
   const initializedExpenseIdRef = useRef<string | null>(null);
 
-  useEffect(() => () => resetState(), [resetState]);
+  useEffect(
+    () => () => {
+      resetState();
+      initializedExpenseIdRef.current = null;
+      initializedGroupIdRef.current = null;
+      initializedFriendIdRef.current = null;
+    },
+    [resetState],
+  );
 
   // TODO: Set this globally from env var with app router later
   const { setMaxUploadFileSizeMB } = useAppStore((s) => s.actions);
@@ -195,7 +203,7 @@ const AddPage: NextPageWithUser<{
     setAmountStr(
       getCurrencyHelpersCached(expenseQuery.data.currency).toUIString(
         expenseQuery.data.amount,
-        false,
+        true,
         true,
       ),
     );

src/tests/addStore.test.ts

@@ -6,7 +6,9 @@ import {
   calculateParticipantSplit,
   calculateSplitShareBasedOnAmount,
   initSplitShares,
+  useAddExpenseStore,
 } from '~/store/addStore';
+import { getCurrencyHelpers } from '~/utils/numbers';
 
 // Mock dependencies
 jest.mock('~/utils/array', () => ({
@@ -1079,3 +1081,51 @@ describe('Function Reversibility Tests', () => {
     });
   });
 });
+
+// Regression test for #658: editing a negative expense must preserve the sign
+describe('useAddExpenseStore sign preservation on edit (#658)', () => {
+  const { toUIString } = getCurrencyHelpers({ locale: 'en-US', currency: 'USD' });
+  const { actions } = useAddExpenseStore.getState();
+
+  beforeEach(() => {
+    actions.resetState();
+  });
+
+  it('loads a negative expense with the minus sign visible in amountStr', () => {
+    actions.setAmount(-20000n);
+    actions.setAmountStr(toUIString(-20000n, true, true));
+
+    const state = useAddExpenseStore.getState();
+    expect(state.amountStr).toBe('-200');
+    expect(state.isNegative).toBe(true);
+    expect(state.amount).toBe(20000n);
+  });
+
+  it('preserves the sign when the user edits digits without removing the minus', () => {
+    actions.setAmount(-20000n);
+    actions.setAmountStr(toUIString(-20000n, true, true));
+
+    // Simulate the user changing -200 to -200.01 via the input
+    actions.setAmountStr('-200.01');
+    actions.setAmount(-20001n);
+
+    const state = useAddExpenseStore.getState();
+    expect(state.amountStr).toBe('-200.01');
+    expect(state.isNegative).toBe(true);
+    expect(state.amount).toBe(20001n);
+  });
+
+  it('flips the sign when the user deletes the minus and edits the value', () => {
+    actions.setAmount(-20000n);
+    actions.setAmountStr(toUIString(-20000n, true, true));
+
+    // Simulate the user deleting the minus and changing the value to 200.01
+    actions.setAmountStr('200.01');
+    actions.setAmount(20001n);
+
+    const state = useAddExpenseStore.getState();
+    expect(state.amountStr).toBe('200.01');
+    expect(state.isNegative).toBe(false);
+    expect(state.amount).toBe(20001n);
+  });
+});

src/tests/number.test.ts

@@ -46,6 +46,15 @@ describe('getCurrencyHelpers', () => {
         ])('should format %p as %p with signed flag', (value, expected) => {
           expect(toUIString(value, true)).toBe(expected);
         });
+
+        it.each([
+          [12345n, '123.45'],
+          [-12345n, '-123.45'],
+          [-50n, '-0.5'],
+          [-0n, '0'],
+        ])('should format %p as %p with signed flag and hideSymbol', (value, expected) => {
+          expect(toUIString(value, true, true)).toBe(expected);
+        });
       });
       describe('JPY (no decimals)', () => {
         const currency = 'JPY';
@@ -173,6 +182,38 @@ describe('getCurrencyHelpers', () => {
       expect(sanitizeInput(input, true)).toBe(expected);
     });
   });
+
+  describe('parseToCleanString', () => {
+    const { parseToCleanString } = getCurrencyHelpers({
+      locale: 'en-US',
+      currency: 'USD',
+    });
+
+    it.each([
+      ['-200', '-200'],
+      ['-200.01', '-200.01'],
+      ['--200', '-200'],
+      ['-$200.00', '-200.00'],
+    ])('should keep the minus sign for %p with signed flag', (input, expected) => {
+      expect(parseToCleanString(input, true)).toBe(expected);
+    });
+
+    it.each([
+      [-20000n, '-200.00'],
+      [-12345n, '-123.45'],
+      [-50n, '-0.50'],
+      [-0n, '0.00'],
+    ])('should keep the minus sign for bigint %p with signed flag', (value, expected) => {
+      expect(parseToCleanString(value, true)).toBe(expected);
+    });
+
+    it.each([
+      ['-200', '200'],
+      ['-123.45', '123.45'],
+    ])('should drop the minus sign for %p without signed flag', (input, expected) => {
+      expect(parseToCleanString(input)).toBe(expected);
+    });
+  });
 });
 
 describe('currencyConversion', () => {

src/utils/numbers.ts

@@ -130,8 +130,8 @@ export const getCurrencyHelpers = ({
     return cleaned;
   };
 
-  const normalizeToMaxLength = (inputString: string) => {
-    const sanitized = sanitizeInput(inputString);
+  const normalizeToMaxLength = (inputString: string, signed = false) => {
+    const sanitized = sanitizeInput(inputString, signed);
     const trimmedExceedingDecimals = trimExceedingDecimals(sanitized);
     return trimmedExceedingDecimals.endsWith(decimalSeparator)
       ? trimmedExceedingDecimals.slice(0, -1)
@@ -173,7 +173,7 @@ export const getCurrencyHelpers = ({
     }
 
     if (typeof value === 'string') {
-      return normalizeToMaxLength(value);
+      return normalizeToMaxLength(value, signed);
     }
 
     return '';
@@ -233,7 +233,6 @@ export const getCurrencyHelpers = ({
   return {
     parseToCleanString,
     toUIString,
-    toUIStringSigned: (value: unknown) => toUIString(value, true),
     format,
     formatter,
     sanitizeInput,