feat(cli): Experimental config for swift-tools-version in SPM apps

cli/src/declarations.ts

@@ -509,6 +509,42 @@ export interface CapacitorConfig {
     };
   };
 
+  experimental?: {
+    /**
+     * Experimental iOS-specific configuration.
+     *
+     * These options may change or be removed in future versions.
+     *
+     * @since 8.2.0
+     */
+    ios?: {
+      /**
+       * Swift Package Manager (SPM) specific configuration.
+       *
+       * @since 8.2.0
+       */
+      spm?: {
+        /**
+         * Swift tools version to use in Package.swift header.
+         *
+         * Defines the minimum version of the Swift compiler version required to build your app.
+         * For more information check the [swift documentation](https://docs.swift.org/swiftpm/documentation/packagemanagerdocs/settingswifttoolsversion/)
+         *
+         * Warning: Capacitor does not officially support Swift 6 yet.
+         * Setting this property to 6.0 or higher may cause issues.
+         * If you need to set this property to 6.0 or higher, make sure to throughrouly test your iOS app.
+         *
+         * This setting may graduate to `ios.spm.swiftToolsVersion` in a future major release.
+         *
+         * @since 8.2.0
+         * @default '5.9'
+         * @example '6.1'
+         */
+        swiftToolsVersion?: string;
+      };
+    };
+  };
+
   server?: {
     /**
      * Configure the local hostname of the device.

cli/src/ios/common.ts

@@ -11,6 +11,7 @@ import type { Config } from '../definitions';
 import { logger } from '../log';
 import { PluginType, getPluginPlatform } from '../plugin';
 import type { Plugin } from '../plugin';
+import { checkSwiftToolsVersion } from '../util/spm';
 import { isInstalled, runCommand } from '../util/subprocess';
 
 export async function checkIOSPackage(config: Config): Promise<string | null> {
@@ -32,6 +33,11 @@ export async function getCommonChecks(config: Config): Promise<CheckFunction[]>
     checks.push(() => checkBundler(config));
   } else if ((await config.ios.packageManager) === 'Cocoapods') {
     checks.push(() => checkCocoaPods(config));
+  } else if ((await config.ios.packageManager) === 'SPM') {
+    const swiftToolsVersion = config.app.extConfig.experimental?.ios?.spm?.swiftToolsVersion;
+    if (swiftToolsVersion) {
+      checks.push(() => checkSwiftToolsVersion(config, swiftToolsVersion));
+    }
   }
   return checks;
 }

cli/src/util/spm.ts

@@ -98,8 +98,9 @@ export async function removeCocoapodsFiles(config: Config): Promise<void> {
 export async function generatePackageText(config: Config, plugins: Plugin[]): Promise<string> {
   const iosPlatformVersion = await getCapacitorPackageVersion(config, config.ios.name);
   const iosVersion = getMajoriOSVersion(config);
+  const swiftToolsVersion = config.app.extConfig.experimental?.ios?.spm?.swiftToolsVersion ?? '5.9';
 
-  let packageSwiftText = `// swift-tools-version: 5.9
+  let packageSwiftText = `// swift-tools-version: ${swiftToolsVersion}
 import PackageDescription
 
 // DO NOT MODIFY THIS FILE - managed by Capacitor CLI commands
@@ -188,6 +189,23 @@ export async function addInfoPlistDebugIfNeeded(config: Config): Promise<void> {
   }
 }
 
+export async function checkSwiftToolsVersion(config: Config, version: string | undefined): Promise<string | null> {
+  if (!version) {
+    return null;
+  }
+
+  const swiftToolsVersionRegex = /^[0-9]+\.[0-9]+(\.[0-9]+)?$/;
+
+  if (!swiftToolsVersionRegex.test(version)) {
+    return (
+      `Invalid Swift tools version: "${version}".\n` +
+      `The Swift tools version must be in major.minor or major.minor.patch format (e.g., "5.9", "6.0", "5.9.2").`
+    );
+  }
+
+  return null;
+}
+
 // Private Functions
 
 async function pluginsWithPackageSwift(plugins: Plugin[]): Promise<Plugin[]> {