Let calculateFee handle fee amounts that exceed the safe integer range

CHANGELOG.md

@@ -10,6 +10,11 @@ and this project adheres to
 
 - @cosmjs/math: Add `Decimal.floor` and `Decimal.ceil`.
 
+### Changed
+
+- @cosmjs/stargate: Let `calculateFee` handle fee amounts that exceed the safe
+  integer range.
+
 ## [0.28.4] - 2022-04-15
 
 ### Added

packages/stargate/src/fee.spec.ts

@@ -93,4 +93,15 @@ describe("calculateFee", () => {
       gas: "80000",
     });
   });
+
+  it("works with large gas price", () => {
+    // "The default gas price is 5000000000000 (5e^12), as the native coin has 18 decimals it is exceeding the max safe integer"
+    // https://github.com/cosmos/cosmjs/issues/1134
+    const gasPrice = GasPrice.fromString("5000000000000tiny");
+    const fee = calculateFee(500_000, gasPrice);
+    expect(fee).toEqual({
+      amount: [{ amount: "2500000000000000000", denom: "tiny" }],
+      gas: "500000",
+    });
+  });
 });

packages/stargate/src/fee.ts

@@ -60,7 +60,9 @@ export class GasPrice {
 export function calculateFee(gasLimit: number, gasPrice: GasPrice | string): StdFee {
   const processedGasPrice = typeof gasPrice === "string" ? GasPrice.fromString(gasPrice) : gasPrice;
   const { denom, amount: gasPriceAmount } = processedGasPrice;
-  const amount = Math.ceil(gasPriceAmount.multiply(new Uint53(gasLimit)).toFloatApproximation());
+  // Note: Amount can exceed the safe integer range (https://github.com/cosmos/cosmjs/issues/1134),
+  // which we handle by converting from Decimal to string without going through number.
+  const amount = gasPriceAmount.multiply(new Uint53(gasLimit)).ceil().toString();
   return {
     amount: coins(amount, denom),
     gas: gasLimit.toString(),