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Skillscapacitor-plugin-spm-support

capacitor-plugin-spm-support

Coding & development

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Updated 10-15 15:50

About this skill

Add Swift Package Manager Support to a Capacitor Plugin

Make a plugin installable in SPM-based Capacitor apps while keeping its podspec for CocoaPods apps.

When to Use

TRIGGER when:

  • A plugin repo has ios/Plugin/*.swift + *.m/*.h with CAP_PLUGIN(...) and no root Package.swift.
  • An app's npx cap sync ios prints <plugin id> does not have a Package.swift for a plugin the user maintains.
  • A plugin works with CocoaPods but JS gets "X" plugin is not implemented on ios in SPM apps.
  • Preparing a plugin for Capacitor 9 / CocoaPods Trunk read-only.

Do not use:

  • App-side CocoaPods removal -> cocoapods-to-spm.
  • Capacitor major bumps of a plugin -> capacitor-plugin-upgrades, capacitor-plugin-upgrade-v8-to-v9.
  • Android-only plugin work, or non-Capacitor (pure Cordova, React Native) plugins.

Rules the CLI Enforces (non-obvious)

  • Package.swift must be at the npm package root (next to package.json), not under ios/. The app CLI only checks <plugin root>/Package.swift.
  • The CLI references the plugin in the app's CapApp-SPM/Package.swift as .package(name: "<Name>", path: ...) and .product(name: "<Name>", package: "<Name>"), where <Name> is derived from the npm name: drop @, turn / and - into word breaks, PascalCase. @capgo/capacitor-updater -> CapgoCapacitorUpdater, @acme/capacitor-foo-bar -> AcmeCapacitorFooBar. The Package(name:) and the .library(name:) product must both equal <Name>, or app builds fail to resolve the product.
  • Runtime registration uses ios/App/App/capacitor.config.json -> packageClassList, filled by scanning the plugin's iOS sources (capacitor.ios.src in package.json, default ios) for @objc(ClassName). Keep @objc(<Class>Plugin) on the class; without it the plugin is never registered.
  • The capacitor-swift-pm dependency must use from: "<major>.0.0". If the major differs from the app's Capacitor, app sync rewrites it in node_modules and warns <id> is built for Capacitor <N>, it might cause issues.
  • Capacitor 9: depend only on .product(name: "Capacitor", package: "capacitor-swift-pm"). Remove the unconditional Cordova product; it is only present in apps that install a Cordova plugin. Keep it on Capacitor 8 only if your code imports Cordova.

Procedure

1. Inspect

Read package.json (name, files, capacitor.ios.src, scripts), the .podspec (s.name, s.ios.deployment_target, s.dependency, s.resources, s.vendored_frameworks), every file in ios/, and the CAP_PLUGIN(...) macro in the .m file.

Record: SPM <Name> (rule above), class name, jsName, every CAP_PLUGIN_METHOD(name, returnType), iOS deployment target, third-party pods, resources, vendored frameworks, ObjC/C sources other than the bridge.

Check each third-party pod has an official SPM package. Report any that do not before editing; ask whether to drop, vendor as .xcframework, or keep the plugin CocoaPods-only.

2. Fast path: converter

If the iOS code is Swift-only apart from the [Name]Plugin.m / .h bridge, the official converter does most of the work (adds CAPBridgedPlugin, creates Package.swift, moves code to ios/Sources and ios/Tests, removes Plugin.xcodeproj/xcworkspace/Podfile, updates podspec source_files, files, and verify:ios): https://github.com/ionic-team/capacitor-plugin-converter. Review its diff against the rules above, especially the package/product name.

3. Manual conversion

  1. Move sources: ios/Plugin/ -> ios/Sources/<ClassName>/, tests -> ios/Tests/<ClassName>Tests/.
  2. Convert the class (keep method names and return types exactly as in the .m macro): 
    import Capacitor

@objc(FooPlugin)
public class FooPlugin: CAPPlugin, CAPBridgedPlugin {
    public let identifier = "FooPlugin"     // first CAP_PLUGIN argument
    public let jsName = "Foo"               // second CAP_PLUGIN argument (registerPlugin name)
    public let pluginMethods: [CAPPluginMethod] = [
        CAPPluginMethod(name: "doThing", returnType: CAPPluginReturnPromise),
        CAPPluginMethod(name: "watch", returnType: CAPPluginReturnCallback),
        CAPPluginMethod(name: "fireAndForget", returnType: CAPPluginReturnNone)
    ]
    @objc func doThing(_ call: CAPPluginCall) { call.resolve() }
}
  3. Delete FooPlugin.m and FooPlugin.h (the CAP_PLUGIN bridge) and stale Plugin.xcodeproj, Plugin.xcworkspace, Podfile, Info.plist files under ios/.
  4. Add root Package.swift. Template and variants (resources, binary targets, third-party packages, mixed ObjC) in references/package-swift-templates.md.
  5. Update the podspec: s.source_files = 'ios/Sources/**/*.{swift,h,m,c,cc,mm,cpp}', keep s.dependency 'Capacitor', and mirror deployment target and resources.
  6. Update package.json:
    • files: add ios/Sources/, Package.swift; keep the .podspec; remove old ios/Plugin/.
    • verify:ios: xcodebuild -scheme <Name> -destination generic/platform=iOS.

Verification

# Package resolves and builds standalone (from plugin root)
swift package describe >/dev/null && echo "manifest ok"
xcodebuild -scheme <Name> -destination generic/platform=iOS build
# Published tarball contains the manifest and sources
npm pack --dry-run 2>&1 | grep -E 'Package.swift|ios/Sources'
# No leftover ObjC bridge
grep -rn "CAP_PLUGIN(" ios/ && echo "LEFTOVER BRIDGE"

Then in an SPM example/test app (directory with capacitor.config.*): install the plugin (npm install ../path or a packed tarball), run npx cap sync ios, confirm no does not have a Package.swift warning, confirm <Name> appears in ios/App/CapApp-SPM/Package.swift and the class appears in ios/App/App/capacitor.config.json packageClassList, build, and call one method from JS. Also run pod lib lint (or a CocoaPods example app) if the podspec is still published.

Error Handling

Error Fix
product '<Name>' required by package 'capapp-spm' target 'CapApp-SPM' not found in package '<Name>' Package(name:) / .library(name:) do not match the CLI-derived <Name>.
"Foo" plugin is not implemented on ios Missing @objc(FooPlugin), wrong jsName, or class not in packageClassList; re-sync after fixing.
"Foo.bar()" is not implemented on ios Method missing from pluginMethods or not marked @objc.
No such module 'Capacitor' building the package Missing capacitor-swift-pm dependency or wrong product name.
public headers ("include") directory path for 'X' is invalid or not contained in the target Mixed ObjC target without publicHeadersPath; split ObjC into its own target (see reference).
<id> is built for Capacitor <N>, it might cause issues (in app) Bump capacitor-swift-pm from: to the app's major.
Cordova product missing (Capacitor 9 app) Remove the Cordova product dependency.
Resource not found at runtime Declare resources: and load via Bundle.module, not Bundle.main.

References

Only load when the topic is in play:

  • references/package-swift-templates.md: base manifest, resources and privacy manifest, third-party SPM dependencies, binary .xcframework, mixed Swift/ObjC targets, Capacitor 8 vs 9 dependency blocks.