pod install fails with Xcodeproj unknown attributes and FrozenStringError in Flutter iOS project

[0xDEVAN]

Environment:

• macOS Sonoma
• Xcode 14.5
• CocoaPods 1.15.2
• Flutter 3.0 (if applicable)

Issue Description: Encountered multiple errors while running pod install in the iOS directory of my Flutter project that integrates Firebase. I am using Visual Studio Code as my IDE.

Steps to Reproduce:

1. Open terminal in Visual Studio Code.
2. Navigate to the iOS directory of the project.
3. Execute pod install --repo-update.

Expected Behavior: Pods should install without errors, updating the project dependencies accordingly.

Actual Behavior: Received errors related to unknown attributes in Xcodeproj and a FrozenError when CocoaPods attempted to report the error. The detailed error messages are:

• [!] Xcodeproj doesn't know about the following attributes {"minimizedProjectReferenceProxies"=>"1"} for the 'PBXProject' isa.
• FrozenError: can't modify frozen String

Error Messages: [!] Xcodeproj doesn't know about the following attributes {"minimizedProjectReferenceProxies"=>"1"} for the 'PBXProject' isa. /Library/Ruby/Gems/2.6.0/gems/cocoapods-1.15.2/lib/cocoapods/user_interface/error_report.rb:34 `force_encoding': can't modify frozen String (FrozenError)

Attempts to Resolve:

• Updated CocoaPods to the latest version.
• Checked Xcode compatibility, no issues found on CocoaPods and Xcode release notes.

Please advise on a resolution or workaround

[khoinguyen]

I got similar issue when using xcodeproj 1.25.0,

try to add following to your Gemfile

gem "xcodeproj", "1.24.0"

run bundle install then bundle exec pod install. This solve my issue