fix: Send refuses every amount the confirmation screen would refuse (closes #532)

Send accepted any amount parseFloat() read as above zero, so "1e-3",
"1abc" and an amount with more decimal places than the token has reached
ConfirmTx, which then refused them. isValidAmount() in
src/shared/txValidation.js is now the one check: Review and Max on Send
call it with the token's decimal places, and validateTransfer() calls it
for ConfirmTx, which now also refuses a zero amount and a token amount
with more places than the token has.

Model: opus-5-5

tests/txValidation.test.js

@@ -6,6 +6,7 @@ const {
     FEE_UNAVAILABLE,
     feeReserveWei,
     feeEstimateWei,
+    isValidAmount,
     maxEthAmount,
     maxTokenAmount,
     toFixedPoint,
@@ -33,6 +34,42 @@ describe("toFixedPoint", () => {
     });
 });
 
+// The one amount check the Send screen and the confirmation screen share.
+// The screens themselves are driven in tests/sendAmountRule.test.js.
+describe("isValidAmount", () => {
+    test("accepts a number above zero written as digits and a decimal point", () => {
+        expect(isValidAmount("0.5")).toBe(true);
+        expect(isValidAmount("12")).toBe(true);
+        expect(isValidAmount(".5")).toBe(true);
+        expect(isValidAmount("0.000000000000000001")).toBe(true);
+    });
+
+    test("refuses an exponent, trailing text, zero and a negative amount", () => {
+        expect(isValidAmount("1e-3")).toBe(false);
+        expect(isValidAmount("1abc")).toBe(false);
+        expect(isValidAmount("0")).toBe(false);
+        expect(isValidAmount("0.0")).toBe(false);
+        expect(isValidAmount("-1")).toBe(false);
+        expect(isValidAmount("")).toBe(false);
+        expect(isValidAmount(undefined)).toBe(false);
+    });
+
+    test("refuses more decimal places than the token has", () => {
+        expect(isValidAmount("0.000001", 6)).toBe(true);
+        expect(isValidAmount("0.0000001", 6)).toBe(false);
+        expect(isValidAmount("5", 0)).toBe(true);
+        expect(isValidAmount("0.5", 0)).toBe(false);
+    });
+
+    test("holds ETH, a token of unknown places, and any token to 18 places", () => {
+        const nineteen = "0.0000000000000000001";
+        expect(isValidAmount(nineteen)).toBe(false);
+        expect(isValidAmount(nineteen, null)).toBe(false);
+        expect(isValidAmount(nineteen, 24)).toBe(false);
+        expect(isValidAmount("0.000000000000000001", 24)).toBe(true);
+    });
+});
+
 describe("validateTransfer, native ETH", () => {
     const eth = (over) => ({
         isErc20: false,
@@ -134,6 +171,17 @@ describe("validateTransfer, native ETH", () => {
         ).toEqual({ canSend: false, codes: [CODES.AMOUNT_INVALID] });
     });
 
+    test("rejects a zero amount and an exponent", () => {
+        expect(validateTransfer(eth({ amount: "0" }))).toEqual({
+            canSend: false,
+            codes: [CODES.AMOUNT_INVALID],
+        });
+        expect(validateTransfer(eth({ amount: "1e-3" }))).toEqual({
+            canSend: false,
+            codes: [CODES.AMOUNT_INVALID],
+        });
+    });
+
     test("treats a missing balance as zero, not as unlimited", () => {
         const r = validateTransfer(eth({ ethBalance: undefined }));
         expect(r.codes).toEqual([CODES.INSUFFICIENT_ETH]);
@@ -205,6 +253,16 @@ describe("validateTransfer, ERC-20", () => {
         expect(r).toEqual({ canSend: false, codes: [CODES.AMOUNT_INVALID] });
     });
 
+    test("rejects more decimal places than the token has", () => {
+        const r = validateTransfer(
+            erc20({ amount: "0.0000001", tokenDecimals: 6 }),
+        );
+        expect(r).toEqual({ canSend: false, codes: [CODES.AMOUNT_INVALID] });
+        expect(
+            validateTransfer(erc20({ amount: "0.000001", tokenDecimals: 6 })),
+        ).toEqual({ canSend: true, codes: [] });
+    });
+
     test("treats a missing token balance as zero", () => {
         const r = validateTransfer(erc20({ tokenBalance: undefined }));
         expect(r.codes).toEqual([CODES.INSUFFICIENT_TOKEN]);