Refactor toBaseUnitAmount so that it throws if user supplies unitAmount with too many decimals

2 files changed, 10 insertions, 0 deletions

diff --git a/packages/0x.js/src/0x.ts b/packages/0x.js/src/0x.ts
index 596d6ffba..a18f1fc55 100644
--- a/packages/0x.js/src/0x.ts
+++ b/packages/0x.js/src/0x.ts
@@ -149,6 +149,10 @@ export class ZeroEx {
 
         const unit = new BigNumber(10).pow(decimals);
         const baseUnitAmount = amount.times(unit);
+        const hasDecimals = baseUnitAmount.decimalPlaces() !== 0;
+        if (hasDecimals) {
+            throw new Error(`Invalid unit amount: ${amount.toString()} - Too many decimal places`);
+        }
         return baseUnitAmount;
     }
     /**
diff --git a/packages/0x.js/test/0x.js_test.ts b/packages/0x.js/test/0x.js_test.ts
index 9bf504909..245946a89 100644
--- a/packages/0x.js/test/0x.js_test.ts
+++ b/packages/0x.js/test/0x.js_test.ts
@@ -136,6 +136,12 @@ describe('ZeroEx library', () => {
             const expectedUnitAmount = new BigNumber(1000000000);
             expect(baseUnitAmount).to.be.bignumber.equal(expectedUnitAmount);
         });
+        it('should throw if unitAmount has more decimals then specified as the max decimal precision', () => {
+            const unitAmount = new BigNumber(0.823091);
+            const decimals = 5;
+            expect(() => ZeroEx.toBaseUnitAmount(unitAmount, decimals))
+                .to.throw('Invalid unit amount: 0.823091 - Too many decimal places');
+        });
     });
     describe('#getOrderHashHex', () => {
         const expectedOrderHash = '0x39da987067a3c9e5f1617694f1301326ba8c8b0498ebef5df4863bed394e3c83';