Fallback to simple copy if wasm-opt is not installed

Author: kateinoigakukun

Diff for: Plugins/PackageToJS/Sources/PackageToJS.swift

@@ -117,12 +117,28 @@ extension PackagingSystem {
 }
 
 final class DefaultPackagingSystem: PackagingSystem {
+
+    private let printWarning: (String) -> Void
+
+    init(printWarning: @escaping (String) -> Void) {
+        self.printWarning = printWarning
+    }
+
     func npmInstall(packageDir: String) throws {
         try runCommand(try which("npm"), ["-C", packageDir, "install"])
     }
 
+    lazy var warnMissingWasmOpt: () = {
+        self.printWarning("Warning: wasm-opt is not installed, optimizations will not be applied")
+    }()
+
     func wasmOpt(_ arguments: [String], input: String, output: String) throws {
-        try runCommand(try which("wasm-opt"), arguments + ["-o", output, input])
+        guard let wasmOpt = try? which("wasm-opt") else {
+            _ = warnMissingWasmOpt
+            try FileManager.default.copyItem(atPath: input, toPath: output)
+            return
+        }
+        try runCommand(wasmOpt, arguments + ["-o", output, input])
     }
 
     private func runCommand(_ command: URL, _ arguments: [String]) throws {
@@ -190,7 +206,7 @@ struct PackagingPlanner {
         configuration: String,
         triple: String,
         selfPath: BuildPath = BuildPath(absolute: #filePath),
-        system: any PackagingSystem = DefaultPackagingSystem()
+        system: any PackagingSystem
     ) {
         self.options = options
         self.packageId = packageId

Diff for: Plugins/PackageToJS/Sources/PackageToJSPlugin.swift

@@ -446,6 +446,7 @@ extension PackagingPlanner {
     ) {
         let outputBaseName = outputDir.lastPathComponent
         let (configuration, triple) = PackageToJS.deriveBuildConfiguration(wasmProductArtifact: wasmProductArtifact)
+        let system = DefaultPackagingSystem(printWarning: printStderr)
         self.init(
             options: options,
             packageId: context.package.id,
@@ -454,7 +455,8 @@ extension PackagingPlanner {
             outputDir: BuildPath(absolute: outputDir.path),
             wasmProductArtifact: BuildPath(absolute: wasmProductArtifact.path),
             configuration: configuration,
-            triple: triple
+            triple: triple,
+            system: system
         )
     }
 }