[Infra] Only compile core extension headers once

[ncooke3]

A custom module map was too difficult. I couldn't get CocoaPods to respect the custom module map and stopped when I started to spin on things. I switched to guarding the headers against being included twice. It seems promising so far. I also tried with using #pragma once but that didn't work because (my guess) is that the problem is not that the same header is being included twice, it's that two different headers with the same content are both being included (once in FirebaseCore and once in FirebaseCoreExtension).

Test cases and their results below:

1. Below Podfile uses the current state and fails when building docs.

platform :ios, '13.0'

source 'https://github.com/firebase/SpecsDev.git'
source 'https://github.com/firebase/SpecsStaging.git'
source 'https://cdn.cocoapods.org/'

target 'tempDoc' do
  use_frameworks!

  # Pods for tempDoc
  pod 'FirebaseCrashlytics', '11.5.0'
end

2. Below Podfile uses updated FirebaseCore spec but FirebaseCoreExtension @ main. The framework target builds but the docs target does not build because of the FirebaseCoreExtension @ main does not have guarded headers.

platform :ios, '13.0'

source 'https://github.com/firebase/SpecsDev.git'
source 'https://github.com/firebase/SpecsStaging.git'
source 'https://cdn.cocoapods.org/'

target 'tempDoc' do
  use_frameworks!

  # Pods for tempDoc
  pod 'FirebaseCore', :git => 'https://github.com/firebase/firebase-ios-sdk.git', :branch => 'nc/dup-decls' 
  pod 'FirebaseCrashlytics', '11.5.0'
end

3. Below Podfile uses updated FirebaseCore spec AND updated FirebaseCoreExtension spec. The framework target builds AND the docs target builds.

platform :ios, '13.0'

source 'https://github.com/firebase/SpecsDev.git'
source 'https://github.com/firebase/SpecsStaging.git'
source 'https://cdn.cocoapods.org/'

target 'tempDoc' do
  use_frameworks!

  # Pods for tempDoc
  pod 'FirebaseCore', :git => 'https://github.com/firebase/firebase-ios-sdk.git', :branch => 'nc/dup-decls' 
  pod 'FirebaseCoreExtension', :git => 'https://github.com/firebase/firebase-ios-sdk.git', :branch => 'nc/dup-decls' 
  pod 'FirebaseCrashlytics', '11.5.0'
end

4. Below Podfile uses old product pod and floats to pick up updated FirebaseCore (the floating case). The framework target builds but the docs target does not build because of using the FirebaseCoreExtension @ main.

platform :ios, '13.0'

source 'https://github.com/firebase/SpecsDev.git'
source 'https://github.com/firebase/SpecsStaging.git'
source 'https://cdn.cocoapods.org/'

target 'tempDoc' do
  use_frameworks!

  # Pods for tempDoc
  pod 'FirebaseCore', :git => 'https://github.com/firebase/firebase-ios-sdk.git', :branch => 'nc/dup-decls' 
  pod 'FirebaseCrashlytics', '11.4.0' # older pod!
end

5. Below Podfile uses old product pod and floats to pick up updated FirebaseCore (the floating case). In this example, it floats to pick up FirebaseCoreExtension as well. The framework target builds and the docs target builds.

platform :ios, '13.0'

source 'https://github.com/firebase/SpecsDev.git'
source 'https://github.com/firebase/SpecsStaging.git'
source 'https://cdn.cocoapods.org/'

target 'tempDoc' do
  use_frameworks!

  # Pods for tempDoc
  pod 'FirebaseCore', :git => 'https://github.com/firebase/firebase-ios-sdk.git', :branch => 'nc/dup-decls' 
  pod 'FirebaseCoreExtension', :git => 'https://github.com/firebase/firebase-ios-sdk.git', :branch => 'nc/dup-decls' 
  pod 'FirebaseCrashlytics', '11.4.0' # older pod!
end

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[paulb777]

Are the podspecs published at /Users/nickcooke/Developer/firebase-3 so they show up in the Pods folder instead of the Development Pods folder?

[ncooke3]

Are the podspecs published at /Users/nickcooke/Developer/firebase-3 so they show up in the Pods folder instead of the Development Pods folder?

No, is there a way I can do that locally? Or should I stage these to SpecsDev?

[paulb777]

I'm not aware of how to do it locally. Staging to SpecsDev would be a good way to test

[ncooke3]

Hmm, I actually don't think SpecsDev is that helpful because the spec points the same source that staging does.

[paulb777]

Should be fine to move the tags to the tip of your branch temporarily and use SpecsStaging

[paulb777]

Or CocoaPods-11.5.0 should be sufficient

[ncooke3]

I actually went with this:

 pod 'FirebaseCore', :git => 'https://github.com/firebase/firebase-ios-sdk.git', :branch => 'nc/dup-decls'
 pod 'FirebaseCoreExtension', :git => 'https://github.com/firebase/firebase-ios-sdk.git', :branch => 'nc/dup-decls'
 pod 'FirebaseCrashlytics', '11.4.0'

I updated the PR description and the results were the same.

[paulb777]

LGTM

[ncooke3]

Merged and moving tags to get coverage in the nightlies.

[paulb777]

Confirmed the repro in #13756 now successfully builds docs when pointing at SpecsStaging.

[andrewheard]

Nice solution, @ncooke3!