Try splitting modules

Package.swift

@@ -3,6 +3,8 @@
 
 import PackageDescription
 
+let dependencyOfWebIDLToSwift: [Target.Dependency] = ["ECMAScript", "JavaScriptKit", .product(name: "JavaScriptEventLoop", package: "JavaScriptKit")]
+
 let package = Package(
     name: "DOMKit",
     products: [
@@ -13,7 +15,7 @@ let package = Package(
             name: "DOMKit",
             targets: ["DOMKit"]),
         .library(name: "WebIDL", targets: ["WebIDL"]),
-        .executable(name: "WebIDLToSwift", targets: ["WebIDLToSwift"]),
+        .executable(name: "idl2swift", targets: ["idl2swift"]),
     ],
     dependencies: [
         .package(
@@ -26,13 +28,22 @@ let package = Package(
             dependencies: ["DOMKit"]),
         .target(
             name: "DOMKit",
-            dependencies: ["JavaScriptKit", .product(name: "JavaScriptEventLoop", package: "JavaScriptKit")]),
+            dependencies: dependencyOfWebIDLToSwift),
+        // This support library should be moved to JavaScriptKit
+        .target(name: "ECMAScript", dependencies: [
+            "JavaScriptKit",
+            .product(name: "JavaScriptEventLoop", package: "JavaScriptKit")]),
         .target(name: "WebIDL"),
         .target(
             name: "WebIDLToSwift",
             dependencies: ["WebIDL"]),
+        .target(
+            name: "idl2swift",
+            dependencies: ["WebIDLToSwift"]),
         .testTarget(
             name: "DOMKitTests",
             dependencies: ["DOMKit"]),
+        .testTarget(
+            name: "WebIDLToSwiftTests", dependencies: ["WebIDLToSwift"]),
     ]
 )

Sources/DOMKit/CanvasImageSource.swift

@@ -0,0 +1 @@
+