remove ineffective invariant usages, fixes #2258 (#2693)

* remove ineffective invariant usages

* fix flow err

* fix tests

* fix tests

* use throw

src/createNavigationContainer.js

@@ -1,7 +1,6 @@
 /* @flow */
 
 import React from 'react';
-import invariant from './utils/invariant';
 import { BackHandler, Linking } from './PlatformHelpers';
 import NavigationActions from './NavigationActions';
 import addNavigationHelpers from './addNavigationHelpers';
@@ -74,8 +73,8 @@ export default function createNavigationContainer<S: *, O>(
 
       const keys = Object.keys(containerProps);
 
-      invariant(
-        keys.length === 0,
+      if (keys.length !== 0) {
+        throw new Error(
           'This navigator has both navigation and container props, so it is ' +
             `unclear if it should own its own state. Remove props: "${keys.join(
               ', '
@@ -84,6 +83,7 @@ export default function createNavigationContainer<S: *, O>(
             'navigator should maintain its own state, do not pass a navigation prop.'
         );
       }
+    }
 
     _urlToPathAndParams(url: string) {
       const params = {};

src/routers/TabRouter.js

@@ -45,11 +45,12 @@ export default (
       tabRouters[routeName] = routeConfig.screen.router;
     }
   });
-  invariant(
-    initialRouteIndex !== -1,
+  if (initialRouteIndex === -1) {
+    throw new Error(
       `Invalid initialRouteName '${initialRouteName}' for TabRouter. ` +
         `Should be one of ${order.map((n: *) => `"${n}"`).join(', ')}`
     );
+  }
   return {
     getStateForAction(
       action: NavigationAction | { action: NavigationAction },

src/routers/createConfigGetter.js

@@ -63,10 +63,11 @@ export default (
   let outputConfig = {};
 
   if (Component.router) {
-    invariant(
-      route && routes && index != null,
+    if (!route || !routes || index == null) {
+      throw new Error(
         `Expect nav state to have routes and index, ${JSON.stringify(route)}`
       );
+    }
     const childRoute = routes[index];
     const childNavigation = addNavigationHelpers({
       state: childRoute,

src/routers/getScreenForRouteName.js

@@ -17,13 +17,14 @@ export default function getScreenForRouteName( // eslint-disable-line consistent
 ): NavigationComponent {
   const routeConfig = routeConfigs[routeName];
 
-  invariant(
-    routeConfig,
+  if (!routeConfig) {
+    throw new Error(
       `There is no route defined for key ${routeName}.\n` +
         `Must be one of: ${Object.keys(routeConfigs)
           .map((a: string) => `'${a}'`)
           .join(',')}`
     );
+  }
 
   if (routeConfig.screen) {
     return routeConfig.screen;
@@ -41,5 +42,5 @@ export default function getScreenForRouteName( // eslint-disable-line consistent
     return screen;
   }
 
-  invariant(false, `Route ${routeName} must define a screen or a getScreen.`);
+  throw new Error(`Route ${routeName} must define a screen or a getScreen.`);
 }

src/routers/validateRouteConfigMap.js

@@ -18,8 +18,8 @@ function validateRouteConfigMap(routeConfigs: NavigationRouteConfigMap) {
   routeNames.forEach((routeName: string) => {
     const routeConfig = routeConfigs[routeName];
 
-    invariant(
-      routeConfig.screen || routeConfig.getScreen,
+    if (!routeConfig.screen && !routeConfig.getScreen) {
+      throw new Error(
         `Route '${routeName}' should declare a screen. ` +
           'For example:\n\n' +
           "import MyScreen from './MyScreen';\n" +
@@ -28,18 +28,15 @@ function validateRouteConfigMap(routeConfigs: NavigationRouteConfigMap) {
           '  screen: MyScreen,\n' +
           '}'
       );
-
-    if (routeConfig.screen && routeConfig.getScreen) {
-      invariant(
-        false,
+    } else if (routeConfig.screen && routeConfig.getScreen) {
+      throw new Error(
         `Route '${routeName}' should declare a screen or ` +
           'a getScreen, not both.'
       );
     }
 
-    if (routeConfig.screen) {
-      invariant(
-        typeof routeConfig.screen === 'function',
+    if (routeConfig.screen && typeof routeConfig.screen !== 'function') {
+      throw new Error(
         `The component for route '${routeName}' must be a ` +
           'React component. For example:\n\n' +
           "import MyScreen from './MyScreen';\n" +

src/routers/validateScreenOptions.js

@@ -1,5 +1,4 @@
 /* @flow */
-import invariant from '../utils/invariant';
 
 import type { NavigationRoute } from '../TypeDefinition';
 
@@ -15,8 +14,7 @@ export default (screenOptions: *, route: NavigationRoute) => {
   const deprecatedKey = keys.find((key: *) => deprecatedKeys.includes(key));
 
   if (typeof screenOptions.title === 'function') {
-    invariant(
-      false,
+    throw new Error(
       [
         `\`title\` cannot be defined as a function in navigation options for \`${route.routeName}\` screen. \n`,
         'Try replacing the following:',
@@ -33,8 +31,7 @@ export default (screenOptions: *, route: NavigationRoute) => {
   }
 
   if (deprecatedKey && typeof screenOptions[deprecatedKey] === 'function') {
-    invariant(
-      false,
+    throw new Error(
       [
         `\`${deprecatedKey}\` cannot be defined as a function in navigation options for \`${route.routeName}\` screen. \n`,
         'Try replacing the following:',
@@ -53,8 +50,7 @@ export default (screenOptions: *, route: NavigationRoute) => {
   }
 
   if (deprecatedKey && typeof screenOptions[deprecatedKey] === 'object') {
-    invariant(
-      false,
+    throw new Error(
       [
         `Invalid key \`${deprecatedKey}\` defined in navigation options for \`${route.routeName}\` screen.`,
         '\n',