How to set FIRAnalyticsDebugEnabled WITHOUT launch arguments

firebaseDebug.swift

UserDefaults.standard.set("1", forKey: "/google/measurement/debug_mode")

This is an implementation detail which may change by google at any point. Launch Argument values are converted to preferences in user default at runtime. (Read more here)

In addition to that it seems like google maps from FIRAnalyticsDebugEnabled to /google/measurement/debug_mode at some point in the build process. I figured that out by dumping the user defaults with and without the launch argument with the following code:

        for (key, value) in UserDefaults.standard.dictionaryRepresentation() {
            print("\(key) = \(value) \n")
        }

Why go through all this? Because most CI/deploy build systems don't support passing runtime argument values and the alternative is to figure out how to do it in the command line for xcodebuild command. Instead, by adding this to you track code conditionalized on the way you use to determine the environment of your liking.