Setting up library with CocoaPods and Swift Package Manager - ios

Question

I have created a swift (iOS/MacOS) library on CocoaPods (BillboardSwiftLibrary). Generally, it has its assets and Classes folders which contain the source files.
I want my library to support Swift Package Manager, so I moved the source files from the Classes folder into a Sources folder outside the pod. However, they are still accessible from the Development pods.
Now my library won't build for Cocoapods launch but compiles for Swift Package Manager, I get the error below when I run pod lib lint BillboardSwiftLibrary.podspec
ERROR | file patterns: The source_files pattern did not match any
file.

Answer 1

I wrote a long series from scratch about "Creating iOS framework with CocoaPods, Carthage, SPM support and Travis for running test and Fastlane for release automation" on Medium. I hope it helps.
Creating Swift framework is easy but adding CocoaPods, Carthage and Swift Package Manager support at the same time can sounds like scary in the first place. In addition to that adding Travis to run test for all commits and adding Fastlane to automate release processes for all dependency managers looks like a horror movie. But don’t be afraid. After you finished this series, you can easily create your own Swift frameworks that uses all these tools to make it perfect!
Part 1 — Create CocoaPod and release it.: You will create your own CocoaPod and release it.
Part 2 — Add Carthage support: Your CocoaPod that is created and released at Part 1 will be installed via Carthage.
Part 3 — Add Swift Package Manager support: Your CocoaPod that is created and released at Part 1 will be installed via Swift Package Manager.
Part 4 — Integrate Travis to build example project and run tests for framework: Your framework that can be installed via CocoaPods, Carthage and Swift Package Manager runs tests automatically on Travis for every push on GitHub.
Part 5 — Integrate Fastlane to automate release processes by running just one line of command.:
Every time you want to release new version of your framework via CocoaPods, Carthage and Swift Package Manager, you have to go through following steps:
1- Implement changes for new version
2- Run tests to be sure they are working
3- Commit and push changes for new version.
4- Tag new version to git
git tag 0.1.1
git push origin 0.1.1
Carthage and Swift Package Manager installs your framework from GitHub. If you configure your framework correctly, it can be installed via Carthage or Swift Package Manager after this step. However, CocoaPods has 4 more steps to complete release processes.
5- Increment podspec version => i.e. s.version = '0.1.1'
6- Validate local podspec:
pod lib lint ODCustomFramework.podspec
7- Validate pod for release
pod spec lint ODCustomFramework.podspec
8- Release
pod trunk push ODCustomFramework.podspec
After Travis and Fastlane integration, steps 2, 4, 5, 6, 7 and 8 are automated and those steps are no longer needed to repeat every time you want to release new version.
1- Implement changes for new version
2- Commit and push changes for new version.
3- Travis runs tests automatically after every push.
4- Run following fastlane command to automate all release processes. (step 4, 5, 6, 7, 8)
exec fastlane major | minor | patch

Answer 2

From #Larme's comment, I found the answer.
In your podspec file, change the location of your classes to the sources folder.
So changed my s.source_files from to BillboardSwiftLibrary/Classes/**/* to Sources/**/* and pod lib lint BillboardSwiftLibrary.podspec worked fine.