Let EthereumConnection.getAccount return undefined when balance is 0

CHANGELOG.md

@@ -8,6 +8,7 @@
   by transaction ID.
 * @iov/ethereum: Transaction parsing now works for pre-EIP155 signatures
 * @iov/ethereum: Let listenTx/liveTx return signer's pubkey
+* @iov/ethereum: Let `.getAccount` return undefined when balance is 0
 
 ## 0.12.1
 

packages/iov-ethereum/src/ethereumconnection.spec.ts

@@ -194,23 +194,19 @@ describe("EthereumConnection", () => {
     it("can get account from unused address", async () => {
       pendingWithoutEthereum();
       const connection = await EthereumConnection.establish(testConfig.base);
-      const account = await connection.getAccount({ address: testConfig.unusedAddress });
 
-      // At the moment we cannot distinguish between unused account and balance 0
-      expect(account).toBeDefined();
-      expect(account!.balance[0].quantity).toEqual("0");
+      const account = await connection.getAccount({ address: testConfig.unusedAddress });
+      expect(account).toBeUndefined();
 
       connection.disconnect();
     });
 
     it("can get account from unused pubkey", async () => {
       pendingWithoutEthereum();
       const connection = await EthereumConnection.establish(testConfig.base);
-      const account = await connection.getAccount({ pubkey: testConfig.unusedPubkey });
 
-      // At the moment we cannot distinguish between unused account and balance 0
-      expect(account).toBeDefined();
-      expect(account!.balance[0].quantity).toEqual("0");
+      const account = await connection.getAccount({ pubkey: testConfig.unusedPubkey });
+      expect(account).toBeUndefined();
 
       connection.disconnect();
     });
@@ -472,25 +468,22 @@ describe("EthereumConnection", () => {
         const recipient = await randomAddress();
 
         // setup watching
-        const events = new Array<Account>();
+        const events = new Array<Account | undefined>();
         const subscription = connection.watchAccount({ address: recipient }).subscribe({
           next: event => {
-            if (!event) {
-              subscription.unsubscribe();
-              connection.disconnect();
-              done.fail("Received event undefined, which is not expected in Ethereum");
-              return;
-            }
             events.push(event);
 
-            expect(event.address).toEqual(recipient);
-            expect(event.balance.length).toEqual(1);
-            expect(event.balance[0].fractionalDigits).toEqual(18);
-            expect(event.balance[0].tokenTicker).toEqual("ETH");
+            if (event) {
+              expect(event.address).toEqual(recipient);
+              expect(event.balance.length).toEqual(1);
+              expect(event.balance[0].fractionalDigits).toEqual(18);
+              expect(event.balance[0].tokenTicker).toEqual("ETH");
+            }
 
             if (events.length === 2) {
-              expect(events[0].balance[0].quantity).toEqual("0");
-              expect(events[1].balance[0].quantity).toEqual(defaultAmount.quantity);
+              expect(events[0]).toBeUndefined();
+              expect(events[1]).toBeDefined();
+              expect(events[1]!.balance[0].quantity).toEqual(defaultAmount.quantity);
 
               subscription.unsubscribe();
               connection.disconnect();

packages/iov-ethereum/src/ethereumconnection.ts

@@ -212,14 +212,23 @@ export class EthereumConnection implements BcpConnection {
     }
 
     // eth_getBalance always returns one result. Balance is 0x0 if account does not exist.
+    const ethBalance = Parse.ethereumAmount(decodeHexQuantityString(response.result));
+
+    // Assume the account does not exist when balance is 0. This can lead to cases
+    // where undefined is returned even if the account exists. Keep this as a
+    // workaround until we have a clever and fast way to check account existence.
+    // https://github.com/iov-one/iov-core/issues/676
+    if (ethBalance.quantity === "0") {
+      return undefined;
+    }
 
     const account: Account = {
       address: address,
       pubkey: undefined, // TODO: get from a transaction sent by this address
       balance: [
         {
           tokenName: constants.primaryTokenName,
-          ...Parse.ethereumAmount(decodeHexQuantityString(response.result)),
+          ...ethBalance,
         },
       ],
     };