Error launching React Native app from command line - react-native

Question

I have a React Native app and recently upgraded to React Native 0.55. I previously could run the command react-native run-ios --simulator="iPhone X" to launch the app in the Simulator. Now I cannot, but I can still run the app in Xcode using build and run.
Here is the error from the react-native run-ios --simulator="iPhone X" output:
▸ Compiling RCTBundleURLProvider.m
❌ /dev/node_modules/react-native/React/Base/RCTBundleURLProvider.m:15:53: use of undeclared identifier 'undefined'; did you mean 'underline'?
const NSUInteger kRCTBundleURLProviderDefaultPort = RCT_METRO_PORT;
^~~~~~~~~~~~~~
▸ Compiling RCTLayoutAnimationGroup.m
▸ Compiling RCTNavigator.m
▸ Compiling RCTTabBar.m
** BUILD FAILED **
The following build commands failed:
CompileC /dev/ios/build/Build/Intermediates.noindex/React.build/Debug-iphonesimulator/React.build/Objects-normal/x86_64/RCTBundleURLProvider.o Base/RCTBundleURLProvider.m normal x86_64 objective-c com.apple.compilers.llvm.clang.1_0.compiler
(1 failure)
Installing Build/Products/Debug-iphonesimulator/MyApp.app
An error was encountered processing the command (domain=NSPOSIXErrorDomain, code=2):
Failed to install the requested application
An application bundle was not found at the provided path.
Provide a valid path to the desired application bundle.
Print: Entry, ":CFBundleIdentifier", Does Not Exist
Command failed: /usr/libexec/PlistBuddy -c Print:CFBundleIdentifier Build/Products/Debug-iphonesimulator/MyApp.app/Info.plist
Print: Entry, ":CFBundleIdentifier", Does Not Exist
In case it helps, here's the output of react-native info:
Environment:
OS: macOS High Sierra 10.13.3
Node: 9.5.0
Yarn: 1.3.2
npm: 5.6.0
Watchman: 4.9.0
Xcode: Xcode 9.2 Build version 9C40b
Android Studio: 3.0 AI-171.4443003
Packages: (wanted => installed)
react: ^16.3.0-alpha.1 => 16.3.0-alpha.3
react-native: 0.55.0 => 0.55.0
What's wrong with my setup and how should I fix it?

Answer 1

As a workaround you should try
react-native run-ios --port 8088 or RCT_METRO_PORT=8081 react-native run-ios but unsure if that works.
RCT_METRO_PORT var was added in commit 33d710e8c58ef1dc69816a59ac1cf390894e7cb9 and looks like it breaks versions 0.54/0.55 to run ios apps from the cli.
In the meantime I continue using xcode to run my react-native apps.
Hopefully it can be patched or cherry picked or ultimately be fixed on the next major release.
There is an open GitHub issue about it.