[NFC] BridgeJS: Avoid emitting empty skeletons

Author: kateinoigakukun

Benchmarks/Sources/Generated/JavaScript/BridgeJS.json

@@ -2737,14 +2737,6 @@
   },
   "imported" : {
     "children" : [
-      {
-        "functions" : [
-
-        ],
-        "types" : [
-
-        ]
-      },
       {
         "functions" : [
           {

Examples/PlayBridgeJS/Sources/PlayBridgeJS/Generated/JavaScript/BridgeJS.json

@@ -197,14 +197,6 @@
             ]
           }
         ]
-      },
-      {
-        "functions" : [
-
-        ],
-        "types" : [
-
-        ]
       }
     ]
   },

Plugins/BridgeJS/Sources/BridgeJSCore/SwiftToSkeleton.swift

@@ -66,13 +66,14 @@ public final class SwiftToSkeleton {
                 )
             }
 
-            importedFiles.append(
-                ImportedFileSkeleton(
-                    functions: importCollector.importedFunctions,
-                    types: importCollector.importedTypes,
-                    globalGetters: importCollector.importedGlobalGetters
-                )
+            let importedFile = ImportedFileSkeleton(
+                functions: importCollector.importedFunctions,
+                types: importCollector.importedTypes,
+                globalGetters: importCollector.importedGlobalGetters
             )
+            if !importedFile.isEmpty {
+                importedFiles.append(importedFile)
+            }
             exportCollector.finalize(&exported)
         }
 
@@ -90,7 +91,8 @@ public final class SwiftToSkeleton {
             return module
         }()
 
-        return BridgeJSSkeleton(moduleName: moduleName, exported: exported, imported: importedSkeleton)
+        let exportedSkeleton: ExportedSkeleton? = exported.isEmpty ? nil : exported
+        return BridgeJSSkeleton(moduleName: moduleName, exported: exportedSkeleton, imported: importedSkeleton)
     }
 
     func lookupType(for type: TypeSyntax, errors: inout [DiagnosticError]) -> BridgeType? {

Plugins/BridgeJS/Sources/BridgeJSSkeleton/BridgeJSSkeleton.swift

@@ -624,6 +624,10 @@ public struct ExportedSkeleton: Codable {
         self.protocols.append(contentsOf: other.protocols)
         assert(self.exposeToGlobal == other.exposeToGlobal)
     }
+
+    public var isEmpty: Bool {
+        functions.isEmpty && classes.isEmpty && enums.isEmpty && structs.isEmpty && protocols.isEmpty
+    }
 }
 
 // MARK: - Imported Skeleton
@@ -854,6 +858,10 @@ public struct ImportedFileSkeleton: Codable {
             try container.encode(globalSetters, forKey: .globalSetters)
         }
     }
+
+    public var isEmpty: Bool {
+        functions.isEmpty && types.isEmpty && globalGetters.isEmpty && globalSetters.isEmpty
+    }
 }
 
 public struct ImportedModuleSkeleton: Codable {

Plugins/BridgeJS/Tests/BridgeJSToolTests/BridgeJSCodegenTests.swift

@@ -166,4 +166,22 @@ import Testing
         let skeleton = try swiftAPI.finalize()
         try snapshotCodegen(skeleton: skeleton, name: "CrossFileFunctionTypes.ReverseOrder")
     }
+
+    @Test
+    func codegenSkipsEmptySkeletons() throws {
+        let swiftAPI = SwiftToSkeleton(progress: .silent, moduleName: "TestModule", exposeToGlobal: false)
+        let importedURL = Self.multifileInputsDirectory.appendingPathComponent("ImportedFunctions.swift")
+        swiftAPI.addSourceFile(
+            Parser.parse(source: try String(contentsOf: importedURL, encoding: .utf8)),
+            inputFilePath: "ImportedFunctions.swift"
+        )
+        let exportedOnlyURL = Self.multifileInputsDirectory.appendingPathComponent("ExportedOnly.swift")
+        swiftAPI.addSourceFile(
+            Parser.parse(source: try String(contentsOf: exportedOnlyURL, encoding: .utf8)),
+            inputFilePath: "ExportedOnly.swift"
+        )
+        let skeleton = try swiftAPI.finalize()
+        #expect(skeleton.exported == nil, "Empty exported skeleton should be omitted")
+        try snapshotCodegen(skeleton: skeleton, name: "CrossFileSkipsEmptySkeletons")
+    }
 }

Plugins/BridgeJS/Tests/BridgeJSToolTests/Inputs/MacroSwift/Multifile/ExportedOnly.swift

@@ -0,0 +1,3 @@
+struct ExportedOnly {
+    let value: Int = 0
+}

Plugins/BridgeJS/Tests/BridgeJSToolTests/Inputs/MacroSwift/Multifile/ImportedFunctions.swift

@@ -0,0 +1 @@
+@JSFunction func fetchNumber() throws(JSException) -> Int

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSCodegenTests/CrossFileSkipsEmptySkeletons.json

@@ -0,0 +1,25 @@
+{
+  "imported" : {
+    "children" : [
+      {
+        "functions" : [
+          {
+            "name" : "fetchNumber",
+            "parameters" : [
+
+            ],
+            "returnType" : {
+              "int" : {
+
+              }
+            }
+          }
+        ],
+        "types" : [
+
+        ]
+      }
+    ]
+  },
+  "moduleName" : "TestModule"
+}

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSCodegenTests/CrossFileSkipsEmptySkeletons.swift

@@ -0,0 +1,16 @@
+#if arch(wasm32)
+@_extern(wasm, module: "TestModule", name: "bjs_fetchNumber")
+fileprivate func bjs_fetchNumber() -> Int32
+#else
+fileprivate func bjs_fetchNumber() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$fetchNumber() throws(JSException) -> Int {
+    let ret = bjs_fetchNumber()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+    return Int.bridgeJSLiftReturn(ret)
+}

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSCodegenTests/GlobalGetter.json

@@ -1,22 +1,4 @@
 {
-  "exported" : {
-    "classes" : [
-
-    ],
-    "enums" : [
-
-    ],
-    "exposeToGlobal" : false,
-    "functions" : [
-
-    ],
-    "protocols" : [
-
-    ],
-    "structs" : [
-
-    ]
-  },
   "imported" : {
     "children" : [
       {