Warn when a native View is marked as @NoBridge (#252)

Author: marcprux

Sources/SkipBuild/SkipProject.swift

@@ -1048,10 +1048,11 @@ public class \(moduleName)Module {
 
             // only create tests if we have specified to do so, and we are not a dependent native module
             let createTestModule = createModuleTests && !isDependentNativeModule && !isNativeAppModule
+            let testsModuleName = moduleName + "Tests"
 
             if createTestModule {
                 let testsURL = try projectFolderURL.append(path: "Tests", create: true)
-                let testDir = try testsURL.append(path: moduleName + "Tests", create: true)
+                let testDir = try testsURL.append(path: testsModuleName, create: true)
                 let testSkipDir = try testDir.append(path: "Skip", create: true)
                 let testSwiftFile = testDir.appending(path: "\(moduleName)Tests.swift")
 
@@ -1301,20 +1302,30 @@ struct TestData : Codable, Hashable {
 
                 try testCaseCode.write(to: testSwiftFile, atomically: false, encoding: .utf8)
 
-                let skipYamlAppTests = """
-                # # Skip configuration for \(moduleName) module
-                #build:
-                #  contents:
-                """
+                var testSkipYaml = """
+                # Skip configuration for \(testsModuleName) module
 
-                let skipYamlModuleTests = """
-                # # Skip configuration for \(moduleName) module
                 #build:
                 #  contents:
+
                 """
 
+                if moduleMode.isNative {
+                    // The test target for a natively-compiled Skip Fuse module must itself be transpiled: its
+                    // XCTest cases are transpiled to JUnit tests so the test harness can collect the results.
+                    // A native test target would have its test classes dropped during bridging, leaving no
+                    // tests to run, so it must explicitly opt into transpiled mode.
+                    testSkipYaml += """
+
+                    skip:
+                      mode: 'transpiled'
+
+                    """
+
+                }
+
                 let testSkipYamlFile = testSkipDir.appending(path: "skip.yml")
-                try (isAppModule ? skipYamlAppTests : skipYamlModuleTests).write(to: testSkipYamlFile, atomically: false, encoding: .utf8)
+                try testSkipYaml.write(to: testSkipYamlFile, atomically: false, encoding: .utf8)
 
                 if let resourceFolder = resourceFolder, !resourceFolder.isEmpty {
                     let testResourcesDir = try testDir.append(path: resourceFolder, create: true)
@@ -1438,7 +1449,7 @@ struct TestData : Codable, Hashable {
                 let skipTestDependency = ",\n            \(skipTestProduct)\n        ]"
 
                 targets += """
-                        .testTarget(name: "\(moduleName)Tests", dependencies: [
+                        .testTarget(name: "\(testsModuleName)", dependencies: [
                             "\(moduleName)"\(skipTestDependency)\(resourcesAttribute), plugins: \(skipPluginArray)),
 
                 """

Sources/SkipSyntax/Message.swift

@@ -147,6 +147,11 @@ extension Message {
         return Message(kind: .warning, message: "Skip does not understand complex preprocessor directives. When using Skip-related preprocessor symbols, use only SYMBOL, !SYMBOL, or a list where all symbols are combined by either && or || (but not a combination of the two)", source: source, sourceRange: range)
     }
 
+    static func noBridgeView(_ syntax: SyntaxProtocol, source: Source) -> Message {
+        let range = syntax.range(in: source)
+        return Message(kind: .warning, message: "A SwiftUI View must be bridged in order to render as a native view, but `// SKIP @nobridge` prevents bridging, so this view will not appear on Android. Remove the `// SKIP @nobridge` directive to allow this view to render.", source: source, sourceRange: range)
+    }
+
     // Idea: translate subscripts to Kotlin get/set operator functions
     static func subscriptNotSupported(_ syntax: SyntaxProtocol, source: Source) -> Message {
         let range = syntax.range(in: source)

Sources/SkipSyntax/StatementTypes.swift

@@ -1574,6 +1574,11 @@ class TypeDeclaration: Statement {
                 // We don't care about other protocols
                 inherits = [inheritsView]
             } else {
+                // A native SwiftUI view renders only via its generated bridge, so `// SKIP @nobridge` keeps it
+                // from ever appearing. Warn instead of silently producing a view that never renders.
+                if attributes.isNoBridge, syntaxTree.isBridgeFile, syntaxTree.autoBridge != .none, inherits.contains(where: { isSwiftUIType($0) }) {
+                    syntaxTree.root.messages.append(.noBridgeView(structDecl, source: syntaxTree.source))
+                }
                 return nil
             }
         }
@@ -1628,6 +1633,11 @@ class TypeDeclaration: Statement {
                 // We don't care about other protocols
                 inherits = [inheritsView]
             } else {
+                // A native SwiftUI view renders only via its generated bridge, so `// SKIP @nobridge` keeps it
+                // from ever appearing. Warn instead of silently producing a view that never renders.
+                if attributes.isNoBridge, syntaxTree.isBridgeFile, syntaxTree.autoBridge != .none, inherits.contains(where: { isSwiftUIType($0) }) {
+                    syntaxTree.root.messages.append(.noBridgeView(enumDecl, source: syntaxTree.source))
+                }
                 return nil
             }
         }

Tests/SkipBuildTests/SkipCommandTests.swift

@@ -784,6 +784,20 @@ final class SkipCommandTests: XCTestCase {
 
         """)
 
+        // the test target for a native module must explicitly opt into transpiled mode so its
+        // XCTest cases become JUnit tests (a native test target would have its test classes dropped)
+        let TestsSkipYML = try load("Tests/SomeModuleTests/Skip/skip.yml")
+        XCTAssertEqual(TestsSkipYML, """
+        # Skip configuration for SomeModuleTests module
+
+        #build:
+        #  contents:
+
+        skip:
+          mode: 'transpiled'
+
+        """)
+
         let PackageSwift = try load("Package.swift")
         XCTAssertEqual(PackageSwift, """
         // swift-tools-version: 6.1

Tests/SkipSyntaxTests/BridgeToKotlinTests.swift

@@ -7513,7 +7513,10 @@ final class BridgeToKotlinTests: XCTestCase {
     }
 
     func testNoBridgeView() async throws {
-        try await check(swiftBridge: """
+        // A `// SKIP @nobridge` SwiftUI View renders only via its bridge, so suppressing the bridge would leave
+        // it blank. The view is therefore not bridged (no output), and the transpiler emits a warning
+        // explaining that the view must be bridged in order to render as a native view.
+        try await check(expectMessages: true, swiftBridge: """
         import SkipFuseUI
         // SKIP @nobridge
         struct V: View {
@@ -7527,6 +7530,20 @@ final class BridgeToKotlinTests: XCTestCase {
         """, transformers: transformers)
     }
 
+    func testNoBridgeNonView() async throws {
+        // @nobridge still fully suppresses bridging for non-view types, and (unlike a @nobridge View) must
+        // NOT produce the "must be bridged in order to render" warning, which is scoped to SwiftUI views.
+        try await check(swiftBridge: """
+        import SkipFuseUI
+        // SKIP @nobridge
+        public struct Helper {
+            public var count = 1
+        }
+        """, kotlin: """
+        """, swiftBridgeSupport: """
+        """, transformers: transformers)
+    }
+
     func testNoBridgeInFuseModeBlock() async throws {
         try await check(swiftBridge: """
         import SkipFuseUI