BridgeJS: Fix an issue where the skeleton was being treated as a resource

Author: wfltaylor

Plugins/BridgeJS/Sources/BridgeJSBuildPlugin/BridgeJSBuildPlugin.swift

@@ -20,7 +20,6 @@ struct BridgeJSBuildPlugin: BuildToolPlugin {
 
     private func createGenerateCommand(context: PluginContext, target: SwiftSourceModuleTarget) throws -> Command {
         let outputSwiftPath = context.pluginWorkDirectoryURL.appending(path: "BridgeJS.swift")
-        let outputSkeletonPath = context.pluginWorkDirectoryURL.appending(path: "JavaScript/BridgeJS.json")
 
         let inputSwiftFiles = target.sourceFiles.filter {
             !$0.url.path.hasPrefix(context.pluginWorkDirectoryURL.path + "/")
@@ -67,9 +66,14 @@ struct BridgeJSBuildPlugin: BuildToolPlugin {
         for skeleton in dependencySkeletons(context: context, target: target) {
             arguments.append(contentsOf: [
                 "--dependency-skeleton",
-                "\(skeleton.moduleName)=\(skeleton.url.path)",
+                "\(skeleton.moduleName)=\(skeleton.skeletonURL.path)",
             ])
-            inputFiles.append(skeleton.url)
+            // We have to use the Swift file, not the skeleton, as the input file,
+            // since we can’t make the skeleton file an output file without it being
+            // treated as a resource by the build system (and thus included in the
+            // resource bundle). We need to use something as the inputFile to maintain
+            // correct ordering.
+            inputFiles.append(skeleton.bridgeJSSwiftURL)
         }
 
         let allSwiftFiles = inputSwiftFiles + pluginGeneratedSwiftFiles
@@ -80,13 +84,14 @@ struct BridgeJSBuildPlugin: BuildToolPlugin {
             executable: try context.tool(named: "BridgeJSTool").url,
             arguments: arguments,
             inputFiles: inputFiles,
-            outputFiles: [outputSwiftPath, outputSkeletonPath]
+            outputFiles: [outputSwiftPath]
         )
     }
 
     private struct DependencySkeleton {
         let moduleName: String
-        let url: URL
+        let skeletonURL: URL
+        let bridgeJSSwiftURL: URL
     }
 
     /// We only read skeletons from dependencies with a `bridge-js.config.json` file.
@@ -118,7 +123,18 @@ struct BridgeJSBuildPlugin: BuildToolPlugin {
                 packageID: context.package.id,
                 buildPluginWorkDirectoryURL: context.pluginWorkDirectoryURL
             )
-            skeletons.append(DependencySkeleton(moduleName: swiftTarget.name, url: skeletonURL))
+            let bridgeJSSwiftURL = BridgeJSPluginPaths.bridgeJSSwiftURL(
+                targetName: swiftTarget.name,
+                packageID: context.package.id,
+                buildPluginWorkDirectoryURL: context.pluginWorkDirectoryURL
+            )
+            skeletons.append(
+                DependencySkeleton(
+                    moduleName: swiftTarget.name,
+                    skeletonURL: skeletonURL,
+                    bridgeJSSwiftURL: bridgeJSSwiftURL
+                )
+            )
         }
         return skeletons
     }

Plugins/BridgeJS/Sources/BridgeJSPluginUtilities/PluginPaths.swift

@@ -13,11 +13,12 @@ enum BridgeJSPluginPaths {
             .deletingLastPathComponent()
             .deletingLastPathComponent()
             .deletingLastPathComponent()
-        return skeletonURL(
+        return bridgeJSDirectoryURL(
             targetName: targetName,
             packageID: packageID,
             pluginsOutputsRootURL: pluginsOutputsRootURL
         )
+        .appending(path: "JavaScript/BridgeJS.json")
     }
 
     static func skeletonURL(
@@ -32,22 +33,42 @@ enum BridgeJSPluginPaths {
             .deletingLastPathComponent()
             .deletingLastPathComponent()
             .appending(path: "outputs")
-        return skeletonURL(
+        return bridgeJSDirectoryURL(
             targetName: targetName,
             packageID: packageID,
             pluginsOutputsRootURL: pluginsOutputsRootURL
         )
+        .appending(path: "JavaScript/BridgeJS.json")
     }
 
-    private static func skeletonURL(
+    static func bridgeJSSwiftURL(
+        targetName: String,
+        packageID: String,
+        buildPluginWorkDirectoryURL workDirectoryURL: URL
+    ) -> URL {
+        let pluginsOutputsRootURL =
+            workDirectoryURL
+            .deletingLastPathComponent()
+            .deletingLastPathComponent()
+            .deletingLastPathComponent()
+            .deletingLastPathComponent()
+        return bridgeJSDirectoryURL(
+            targetName: targetName,
+            packageID: packageID,
+            pluginsOutputsRootURL: pluginsOutputsRootURL
+        )
+        .appending(path: "BridgeJS.swift")
+    }
+
+    private static func bridgeJSDirectoryURL(
         targetName: String,
         packageID: String,
         pluginsOutputsRootURL: URL
     ) -> URL {
         pluginsOutputsRootURL
             .appending(path: packageID)
             .appending(path: targetName)
-            .appending(path: "destination/BridgeJS/JavaScript/BridgeJS.json")
+            .appending(path: "destination/BridgeJS")
     }
 }
 #endif

Plugins/BridgeJS/Sources/BridgeJSTool/BridgeJSTool.swift

@@ -250,7 +250,13 @@ import BridgeJSUtilities
                 }
             }
 
-            // Write unified skeleton
+            // Write unified skeleton.
+            // Note that for the build system to sequence the BridgeJSBuildPlugin correctly,
+            // the skeleton and the Swift output must form a bijection, i.e. if one changes the
+            // other must also change. This is because we can’t use the BridgeJS.json file
+            // as an outputFile, since it would then be treated as a resource and thus included
+            // in the generated bundle. The invariant currently holds, but if this ever changes the
+            // BridgeJS.swift file could include a hash of the skeleton to maintain it.
             let outputSkeletonURL = outputDirectory.appending(path: "JavaScript/BridgeJS.json")
             try withSpan("Writing output skeleton") {
                 try FileManager.default.createDirectory(