feat(battery_plus): Add Swift Package Manager support

[koji-1009]

Description

Add SPM support.

https://docs.flutter.dev/packages-and-plugins/swift-package-manager/for-plugin-authors

I also noticed an error in the documentation.
Since we need to refer to the documentation when reviewing PRs, it will be draft until the next PR is reviewed.

flutter/website#11020

---

As a working test, I have confirmed that it can be built with flutter 3.24 + CocoaPods, and that it can be built with flutter main channel + SPM.
Note that if you try building with main channel + SPM, you will need to remove some steps from your iOS project, as the script to add Pods is no longer needed.

Related Issues

• Related [Request]: Support Swift Package Manager #3152

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I titled the PR using Conventional Commits.
• I did not modify the CHANGELOG.md nor the plugin version in pubspec.yaml files.
• All existing and new tests are passing.
• The analyzer (flutter analyze) does not report any problems on my PR.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate that with a ! in the title as explained in Conventional Commits).
• No, this is not a breaking change.

[koji-1009]

I would be happy to include flutter/website PR and feel free to review it. There is no need to rush and we would like to discuss how it should be implemented.

[charafau]

hi @koji-1009 ! thanks for contribution. I ran pod lint on macos projects and get few warnings:

➜  battery_plus pod lib lint macos/battery_plus.podspec  --configuration=Debug --skip-tests --use-modular-headers

 -> battery_plus (0.0.1)
    - WARN  | license: Missing license type.
    - WARN  | [OSX] keys: Missing primary key for `source` attribute. The acceptable ones are: `git, hg, http, svn`.
    - NOTE  | xcodebuild:  note: Using codesigning identity override:
    - NOTE  | [OSX] xcodebuild:  note: Building targets in dependency order
    - NOTE  | [OSX] xcodebuild:  note: Target dependency graph (4 targets)
    - NOTE  | [OSX] xcodebuild:  note: Metadata extraction skipped. No AppIntents.framework dependency found. (in target 'battery_plus' from project 'Pods')
    - NOTE  | [OSX] xcodebuild:  note: Metadata extraction skipped. No AppIntents.framework dependency found. (in target 'App' from project 'App')

[!] battery_plus did not pass validation, due to 2 warnings (but you can use `--allow-warnings` to ignore them).
You can use the `--no-clean` option to inspect any issue.
➜  battery_plus pod lib lint macos/battery_plus.podspec  --configuration=Debug --skip-tests --use-modular-headers --use-libraries


 -> battery_plus (0.0.1)
    - WARN  | license: Missing license type.
    - WARN  | [OSX] keys: Missing primary key for `source` attribute. The acceptable ones are: `git, hg, http, svn`.
    - NOTE  | xcodebuild:  note: Using codesigning identity override:
    - NOTE  | [OSX] xcodebuild:  note: Building targets in dependency order
    - NOTE  | [OSX] xcodebuild:  note: Target dependency graph (4 targets)
    - NOTE  | [OSX] xcodebuild:  note: Metadata extraction skipped. No AppIntents.framework dependency found. (in target 'App' from project 'App')

[!] battery_plus did not pass validation, due to 2 warnings (but you can use `--allow-warnings` to ignore them).
You can use the `--no-clean` option to inspect any issue.

not sure if they were there before but it would be nice to fix it

[charafau]

sorry, I think that warning were there before, so let's leave it as it is. Probably fix for different PR.

lgtm

[koji-1009]

The contents of the ios/ directory will not be uploaded to https://cocoapods.org/. So pod spec lint shows multiple problems, but I don't see any major issues.
I'm sure time will solve the problem in the future once the migration from CocoaPods to SPM is complete.

[miquelbeltran]

LGTM, I still want to test this on my devices before merge.

[loic-sharma]

Nit: add new line here

[loic-sharma]

Should batery be battery here?

[vbuberen]

Did some testing on iOS and MacOS and can confirm that everything works as it should in both SPM enabled and disabled modes.

Thanks a lot for your contribution. We are good to merge this PR!