Use case

To support both CocoaPods and Swift Package Manager, dynamic and static linking, two different modulemaps are needed.

CocoaPods modulemap

CocoaPods seems to require the modulemap be a framework module and doesn't use relative paths.

For example,

framework module plugin_name_ios {
  umbrella header "plugin_name_ios-umbrella.h"

  export *
  module * { export * }

  explicit module Test {
    header "PublicHeader_Test.h"
    header "OtherPublicHeader_Test.h"
  }
}

SwiftPM modulemap

SwiftPM requires the modulemap to be named module.modulemap and be located within the include directory. It also doesn't seem to work if defined as a framework module and uses relative paths.

For example,

- framework module plugin_name_ios {
+ module plugin_name_ios {

explicit module Test {
-    header "PublicHeader_Test.h"
+    header "plugin_name_ios/OtherPublicHeader_Test.h"

The problem

The problem is that when you have two modulemaps (most likely also because one is named module.modulemap, which is the implicit modulemap file), this can cause issues:

• Lexical or Preprocessor Issue (Xcode): Redefinition of module 'image_picker_ios' #148307
• https://gist.github.com/loic-sharma/27bd8e3ea0d9ab16cd4b8de03918ec4d

Proposal

It's been pretty difficult to figure out a way to support both CocoaPods and SwiftPM modulemaps. As a result, we're leaning towards eliminating modulemaps in SwiftPM.

Instead of using a modulemap and umbrella header for the SwiftPM integration of plugins, we simply allow all public headers to be available via @import plugin_name_ios.

@import plugin_name_ios;
- @import plugin_name_ios.Test;

The headers are already public and could be imported individually (like #import <plugin_name_ios/PublicHeader_Test.h>), so making them available through the module isn't much worse.

Modulemap and umbrella header should be excluded from SwiftPM target:

        .target(
            name: "plugin_name_ios",
            dependencies: [],
+           exclude: ["cocoapods_plugin_name_ios.modulemap", "plugin_name_ios-umbrella.h"],

Unit tests can also be kept compatible with both CocoaPods and SwiftPM with something like:

#if __has_include(<plugin_name_ios/plugin_name_ios-umbrella.h>)
  @import plugin_name_ios.Test;
#endif

Prototype

flutter/packages@main...vashworth:packages:camera_avfoundation_remove_swiftpm_modulemap

Re-adding SwiftPM .modulemaps

Once the ecosystem has migrated to SwiftPM, we will remove support for CocoaPods. At this point, we should consider re-adding module.modulemaps to the plugins' SwiftPM integration. This step might not be necessary as we plan to rewrite plugins in Swift.