Add a test and improve our redirects

src/pages/App.tsx

@@ -98,6 +98,34 @@ function GoogleAnalyticsReporter({ location: { pathname, search } }: RouteCompon
   return null
 }
 
+// Redirects to swap but only replace the pathname
+function RedirectPathToSwapOnly({ location }: RouteComponentProps) {
+  return <Redirect to={{ ...location, pathname: '/swap' }} />
+}
+
+// Redirects from the /swap/:outputCurrency path to the /swap?outputCurrency=:outputCurrency format
+function RedirectToSwap(props: RouteComponentProps<{ outputCurrency: string }>) {
+  const {
+    location: { search },
+    match: {
+      params: { outputCurrency }
+    }
+  } = props
+
+  return (
+    <Redirect
+      to={{
+        ...props.location,
+        pathname: '/swap',
+        search:
+          search && search.length > 1
+            ? `${search}&outputCurrency=${outputCurrency}`
+            : `?outputCurrency=${outputCurrency}`
+      }}
+    />
+  )
+}
+
 export default function App() {
   return (
     <>
@@ -115,6 +143,7 @@ export default function App() {
                   <NavigationTabs />
                   <Switch>
                     <Route exact strict path="/swap" component={Swap} />
+                    <Route exact strict path="/swap/:outputCurrency" component={RedirectToSwap} />
                     <Route exact strict path="/send" component={Send} />
                     <Route exact strict path="/find" component={Find} />
                     <Route exact strict path="/create" component={Create} />
@@ -153,7 +182,7 @@ export default function App() {
                         }
                       }}
                     />
-                    <Redirect to="/swap" />
+                    <Route component={RedirectPathToSwapOnly} />
                   </Switch>
                 </Body>
               </Web3ReactManager>

src/state/swap/reducer.test.ts

@@ -33,6 +33,22 @@ describe('swap reducer', () => {
       })
     })
 
+    test('does not duplicate eth for invalid output token', () => {
+      store.dispatch(
+        setDefaultsFromURL({
+          chainId: ChainId.MAINNET,
+          queryString: '?outputCurrency=invalid'
+        })
+      )
+
+      expect(store.getState()).toEqual({
+        [Field.INPUT]: { address: '' },
+        [Field.OUTPUT]: { address: WETH[ChainId.MAINNET].address },
+        typedValue: '',
+        independentField: Field.INPUT
+      })
+    })
+
     test('output ETH only', () => {
       store.dispatch(
         setDefaultsFromURL({

src/state/swap/reducer.ts

@@ -54,10 +54,10 @@ export default createReducer<SwapState>(initialState, builder =>
         let inputCurrency = parseCurrencyFromURLParameter(parsedQs.inputCurrency, chainId)
         let outputCurrency = parseCurrencyFromURLParameter(parsedQs.outputCurrency, chainId)
         if (inputCurrency === outputCurrency) {
-          if (typeof parsedQs.inputCurrency === 'string') {
-            outputCurrency = ''
-          } else if (typeof parsedQs.outputCurrency === 'string') {
+          if (typeof parsedQs.outputCurrency === 'string') {
             inputCurrency = ''
+          } else {
+            outputCurrency = ''
           }
         }