Fix bug that occurs when token metadata decimals is undefined. (#1426)

* Fix bug that occurs when token metadata decimals is undefined.

* move toBigNumberOrNull to utils

packages/pipeline/src/parsers/token_metadata/index.ts

@@ -1,9 +1,8 @@
-import { BigNumber } from '@0x/utils';
 import * as R from 'ramda';
 
 import { MetamaskTrustedTokenMeta, ZeroExTrustedTokenMeta } from '../../data_sources/trusted_tokens';
 import { TokenMetadata } from '../../entities';
-import {} from '../../utils';
+import { toBigNumberOrNull } from '../../utils';
 
 /**
  * Parses Metamask's trusted tokens list.
@@ -26,7 +25,7 @@ function parseMetamaskTrustedToken(resp: MetamaskTrustedTokenMeta, address: stri
     const trustedToken = new TokenMetadata();
 
     trustedToken.address = address;
-    trustedToken.decimals = new BigNumber(resp.decimals);
+    trustedToken.decimals = toBigNumberOrNull(resp.decimals);
     trustedToken.symbol = resp.symbol;
     trustedToken.name = resp.name;
     trustedToken.authority = 'metamask';
@@ -38,7 +37,7 @@ function parseZeroExTrustedToken(resp: ZeroExTrustedTokenMeta): TokenMetadata {
     const trustedToken = new TokenMetadata();
 
     trustedToken.address = resp.address;
-    trustedToken.decimals = resp.decimals ? new BigNumber(resp.decimals) : null;
+    trustedToken.decimals = toBigNumberOrNull(resp.decimals);
     trustedToken.symbol = resp.symbol;
     trustedToken.name = resp.name;
     trustedToken.authority = '0x';

packages/pipeline/src/utils/index.ts

@@ -14,6 +14,21 @@ export function bigNumbertoStringOrNull(n: BigNumber): string | null {
     return n.toString();
 }
 
+/**
+ * If value is null or undefined, returns null. Otherwise converts value to a
+ * BigNumber.
+ * @param value A string or number to be converted to a BigNumber
+ */
+export function toBigNumberOrNull(value: string | number | null): BigNumber | null {
+    switch (value) {
+        case null:
+        case undefined:
+            return null;
+        default:
+            return new BigNumber(value);
+    }
+}
+
 /**
  * Logs an error by intelligently checking for `message` and `stack` properties.
  * Intended for use with top-level immediately invoked asynchronous functions.