Fix bug, add test resources, add TODOs

- A few commits ago, the public headers were added to the header search
  paths (HSP) of clients. This meant Clang clients could import public
  headers. One bug fixed in this commit was that the generated interop header
  needed to be added to the HSP. This was done by adding the generated
  interop header to the Product all-product-headers.yaml overlay file.
- A few tests were added/modified to appropriately test that Clang
  clients could import all public headers (including generated ones) of
  a mixed test target.
- A few TODOs related to detecting C++ files were added to be discussed
  during PR review.
- One TODO was added to track a remaining bug: This bug is a warning
  that comes from the generated bridging header being overlayed within
  the public headers directory. Clang will sometimes complain that the
  target's umbrella header (if one exists) does not include the
  generated bridging header.

Author: ncooke3

Fixtures/MixedTargets/BasicMixedTargets/Package.swift

@@ -66,6 +66,10 @@ let package = Package(
         .target(
             name: "MixedTargetWithCustomModuleMap"
         ),
+        .testTarget(
+            name: "MixedTargetWithCustomModuleMapTests",
+            dependencies: ["MixedTargetWithCustomModuleMap"]
+        ), 
 
         // MARK: - MixedTargetWithInvalidCustomModuleMap
         .target(

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/Driver.m

@@ -4,5 +4,5 @@
 #import "Driver.h"
 #import "include/Driver.h"
 
-@implementation Driver
+@implementation MyDriver
 @end

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/Engine.swift

@@ -1,4 +1,4 @@
 import Foundation
 
 // This type is Objective-C compatible and used in `OldCar`.
-@objc public class Engine: NSObject {}
+@objc public class Engine: MyMachine {}

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/Machine.m

@@ -0,0 +1,8 @@
+#import <Foundation/Foundation.h>
+
+// Both import statements should be supported.
+#import "Machine.h"
+#import "include/Machine.h"
+
+@implementation MyMachine
+@end

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/NewCar.swift

@@ -3,6 +3,8 @@ import Foundation
 public class NewCar {
     // `Engine` is defined in Swift.
     var engine: Engine? = nil
-    // `Driver` is defined in Objective-C.
-    var driver: Driver? = nil
+    // `MyDriver` is defined in Objective-C.
+    var driver: MyDriver? = nil
+
+    public init() {}
 }

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/OldCar.m

@@ -7,5 +7,5 @@
 // Import the Swift part of the module.
 #import "MixedTargetWithCustomModuleMap-Swift.h"
 
-@implementation OldCar
+@implementation MyOldCar
 @end

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/include/Driver.h

@@ -1,6 +1,7 @@
 #import <Foundation/Foundation.h>
 
 // This type is Swift compatible and used in `NewCar`.
-@interface Driver : NSObject
+// `My` prefix is to avoid naming collision in test bundle.
+@interface MyDriver : NSObject
 @property(nonnull) NSString* name;
 @end

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/include/Machine.h

@@ -0,0 +1,6 @@
+#import <Foundation/Foundation.h>
+
+// This type is subclassed by the Swift type `Engine`.
+// `My` prefix is to avoid naming collision in test bundle.
+@interface MyMachine : NSObject
+@end

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/include/MixedTarget.h

@@ -1,2 +1,3 @@
+#import "Machine.h"
 #import "OldCar.h"
 #import "Driver.h"

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMap/include/OldCar.h

@@ -6,9 +6,10 @@
 // must be forward declared in headers.
 @class Engine;
 
-@interface OldCar : NSObject
+// `My` prefix is to avoid naming collision in test bundle.
+@interface MyOldCar : NSObject
 // `Engine` is defined in Swift.
 @property(nullable) Engine *engine;
 // `Driver` is defined in Objective-C.
-@property(nullable) Driver *driver;
+@property(nullable) MyDriver *driver;
 @end

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMapAndResources/include/MixedTarget.h renamed to Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMapAndResources/include/MixedTargetWithCustomModuleMapAndResources.h

@@ -1,4 +1,4 @@
 module MixedTargetWithCustomModuleMapAndResources {
-    umbrella header "MixedTarget.h"
+    umbrella header "MixedTargetWithCustomModuleMapAndResources.h"
     export *
 }

Fixtures/MixedTargets/BasicMixedTargets/Sources/MixedTargetWithCustomModuleMapAndResources/include/module.modulemap

@@ -0,0 +1,24 @@
+#import <XCTest/XCTest.h>
+
+#import "BasicMixedTarget-Swift.h"
+#import "BasicMixedTarget/BasicMixedTarget.h"
+
+@interface ObjcBasicMixedTargetTestsViaBridgingHeader : XCTestCase
+
+@end
+
+@implementation ObjcBasicMixedTargetTestsViaBridgingHeader
+
+- (void)testPublicSwiftAPI {
+    // Check that Objective-C compatible Swift API surface is exposed...
+    Engine *engine = [[Engine alloc] init];
+}
+
+- (void)testPublicObjcAPI {
+    // Check that Objective-C API surface is exposed...
+    OldCar *oldCar = [[OldCar alloc] init];
+    Driver *driver = [[Driver alloc] init];
+    CarPart *carPart = [[CarPart alloc] init];
+}
+
+@end

Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetTests/ObjcBasicMixedTargetTestsViaBridgingHeader.m

@@ -2,11 +2,11 @@
 
 @import BasicMixedTarget;
 
-@interface ObjcBasicMixedTargetTests : XCTestCase
+@interface ObjcBasicMixedTargetTestsViaHeaderImport : XCTestCase
 
 @end
 
-@implementation ObjcBasicMixedTargetTests
+@implementation ObjcBasicMixedTargetTestsViaHeaderImport
 
 - (void)testPublicSwiftAPI {
     // Check that Objective-C compatible Swift API surface is exposed...

Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetTests/ObjcBasicMixedTargetTests.m renamed to Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetTests/ObjcBasicMixedTargetTestsViaHeaderImport.m

@@ -0,0 +1,26 @@
+#import <XCTest/XCTest.h>
+
+#import "CarPart.h"
+#import "Driver.h"
+#import "OldCar.h"
+#import "BasicMixedTarget-Swift.h"
+
+@interface ObjcBasicMixedTargetTestsViaModuleImport : XCTestCase
+
+@end
+
+@implementation ObjcBasicMixedTargetTestsViaModuleImport
+
+- (void)testPublicSwiftAPI {
+    // Check that Objective-C compatible Swift API surface is exposed...
+    Engine *engine = [[Engine alloc] init];
+}
+
+- (void)testPublicObjcAPI {
+    // Check that Objective-C API surface is exposed...
+    OldCar *oldCar = [[OldCar alloc] init];
+    Driver *driver = [[Driver alloc] init];
+    CarPart *carPart = [[CarPart alloc] init];
+}
+
+@end

Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetTests/ObjcBasicMixedTargetTestsViaModuleImport.m

@@ -0,0 +1,27 @@
+#import <XCTest/XCTest.h>
+
+// Import the target via header imports.
+#import <BasicMixedTargetWithManualBridgingHeader/BasicMixedTargetWithManualBridgingHeader.h>
+#import <BasicMixedTargetWithManualBridgingHeader/OldPlane.h>
+#import <BasicMixedTargetWithManualBridgingHeader/Pilot.h>
+#import <BasicMixedTargetWithManualBridgingHeader/PlanePart.h>
+#import <BasicMixedTargetWithManualBridgingHeader-Swift.h>
+
+@interface ObjcBasicMixedTargetWithManualBridgingHeaderTestsViaHeaderImport : XCTestCase
+
+@end
+
+@implementation ObjcBasicMixedTargetWithManualBridgingHeaderTestsViaHeaderImport
+
+- (void)testPublicSwiftAPI {
+    // Check that Objective-C compatible Swift API surface is exposed...
+    Engine *engine = [[Engine alloc] init];
+}
+
+- (void)testPublicObjcAPI {
+    // Check that Objective-C API surface is exposed...
+    OldPlane *oldPlane = [[OldPlane alloc] init];
+    Pilot *pilot = [[Pilot alloc] init];
+}
+
+@end

Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetWithManualBridgingHeaderTests/BasicMixedTargetWithNestedUmbrellaHeaderTests.swift renamed to Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetWithManualBridgingHeaderTests/BasicMixedTargetWithManualBridgingHeaderTests.swift

@@ -1,12 +1,13 @@
 #import <XCTest/XCTest.h>
 
+// Import the target via a module import.
 @import BasicMixedTargetWithManualBridgingHeader;
 
-@interface ObjcBasicMixedTargetWithManualBridgingHeaderTests : XCTestCase
+@interface ObjcBasicMixedTargetWithManualBridgingHeaderTestsViaModuleImport : XCTestCase
 
 @end
 
-@implementation ObjcBasicMixedTargetWithManualBridgingHeaderTests
+@implementation ObjcBasicMixedTargetWithManualBridgingHeaderTestsViaModuleImport
 
 - (void)testPublicSwiftAPI {
     // Check that Objective-C compatible Swift API surface is exposed...

Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetWithManualBridgingHeaderTests/ObjcBasicMixedTargetWithManualBridgingHeaderTestsViaHeaderImport.m

@@ -0,0 +1,27 @@
+import XCTest
+import MixedTargetWithCustomModuleMap
+
+final class MixedTargetWithCustomModuleMapTests: XCTestCase {
+
+    func testPublicSwiftAPI() throws {
+        // Check that Swift API surface is exposed...
+        let _ = NewCar()
+        let _ = Engine()
+    }
+
+    func testPublicObjcAPI() throws {
+        // Check that Objective-C API surface is exposed...
+        let _ = MyOldCar()
+        let _ = MyDriver()
+        let _ = MyMachine()
+    }
+
+    func testModulePrefixingWorks() throws {
+        let _ = MixedTargetWithCustomModuleMap.MyMachine()
+        let _ = MixedTargetWithCustomModuleMap.NewCar()
+        let _ = MixedTargetWithCustomModuleMap.Engine()
+        let _ = MixedTargetWithCustomModuleMap.MyOldCar()
+        let _ = MixedTargetWithCustomModuleMap.MyDriver()
+    }
+
+}

Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetWithManualBridgingHeaderTests/ObjcBasicMixedTargetWithNestedUmbrellaHeaderTests.m renamed to Fixtures/MixedTargets/BasicMixedTargets/Tests/BasicMixedTargetWithManualBridgingHeaderTests/ObjcBasicMixedTargetWithManualBridgingHeaderTestsViaModuleImport.m

@@ -0,0 +1,23 @@
+#import <XCTest/XCTest.h>
+
+#import "MixedTargetWithCustomModuleMap/MixedTargetWithCustomModuleMap.h"
+#import "MixedTargetWithCustomModuleMap-Swift.h"
+
+@interface ObjcMixedTargetWithCustomModuleMapTestsViaGeneratedBridgingHeader : XCTestCase
+@end
+
+@implementation ObjcMixedTargetWithCustomModuleMapTestsViaGeneratedBridgingHeader
+
+- (void)testPublicSwiftAPI {
+    // Check that Objective-C compatible Swift API surface is exposed...
+    Engine *engine = [[Engine alloc] init];
+}
+
+- (void)testPublicObjcAPI {
+    // Check that Objective-C API surface is exposed...
+    MyMachine *machine = [[MyMachine alloc] init];
+    MyOldCar *oldCar = [[MyOldCar alloc] init];
+    MyDriver *driver = [[MyDriver alloc] init];
+}
+
+@end

Fixtures/MixedTargets/BasicMixedTargets/Tests/MixedTargetWithCustomModuleMapTests/MixedTargetWithCustomModuleMapTests.swift

@@ -0,0 +1,26 @@
+#import <XCTest/XCTest.h>
+
+#import "Machine.h"
+#import "MixedTarget.h"
+#import "Driver.h"
+#import "OldCar.h"
+#import "MixedTargetWithCustomModuleMap-Swift.h"
+
+@interface ObjcMixedTargetWithCustomModuleMapTestsViaHeaderImport : XCTestCase
+@end
+
+@implementation ObjcMixedTargetWithCustomModuleMapTestsViaHeaderImport
+
+- (void)testPublicSwiftAPI {
+    // Check that Objective-C compatible Swift API surface is exposed...
+    Engine *engine = [[Engine alloc] init];
+}
+
+- (void)testPublicObjcAPI {
+    // Check that Objective-C API surface is exposed...
+    MyMachine *machine = [[MyMachine alloc] init];
+    MyOldCar *oldCar = [[MyOldCar alloc] init];
+    MyDriver *driver = [[MyDriver alloc] init];
+}
+
+@end

Fixtures/MixedTargets/BasicMixedTargets/Tests/MixedTargetWithCustomModuleMapTests/ObjcMixedTargetWithCustomModuleMapTestsViaGeneratedBridgingHeader.m

@@ -0,0 +1,22 @@
+#import <XCTest/XCTest.h>
+
+@import MixedTargetWithCustomModuleMap;
+
+@interface ObjcMixedTargetWithCustomModuleMapTestsViaModuleImport : XCTestCase
+@end
+
+@implementation ObjcMixedTargetWithCustomModuleMapTestsViaModuleImport
+
+- (void)testPublicSwiftAPI {
+    // Check that Objective-C compatible Swift API surface is exposed...
+    Engine *engine = [[Engine alloc] init];
+}
+
+- (void)testPublicObjcAPI {
+    // Check that Objective-C API surface is exposed...
+    MyMachine *machine = [[MyMachine alloc] init];
+    MyOldCar *oldCar = [[MyOldCar alloc] init];
+    MyDriver *driver = [[MyDriver alloc] init];
+}
+
+@end

Fixtures/MixedTargets/BasicMixedTargets/Tests/MixedTargetWithCustomModuleMapTests/ObjcMixedTargetWithCustomModuleMapTestsViaHeaderImport.m

@@ -4,10 +4,10 @@
 #import "ObjcCalculator.h"
 #import "MixedTargetWithPublicCXXAPI-Swift.h"
 
-@interface ObjcMixedTargetWithPublicCXXAPIViaModuleImportTests : XCTestCase
+@interface ObjcMixedTargetWithPublicCXXAPITestsViaHeaderImport : XCTestCase
 @end
 
-@implementation ObjcMixedTargetWithPublicCXXAPIViaModuleImportTests
+@implementation ObjcMixedTargetWithPublicCXXAPITestsViaHeaderImport
 
 - (void)testPublicObjcAPI {
     XCTAssertEqual([ObjcCalculator factorialForInt:5], 120);

Fixtures/MixedTargets/BasicMixedTargets/Tests/MixedTargetWithCustomModuleMapTests/ObjcMixedTargetWithCustomModuleMapTestsViaModuleImport.m

@@ -2,10 +2,10 @@
 
 @import MixedTargetWithPublicCXXAPI;
 
-@interface ObjcMixedTargetWithPublicCXXAPIViaModuleImportTests : XCTestCase
+@interface ObjcMixedTargetWithPublicCXXAPITestsViaModuleImport : XCTestCase
 @end
 
-@implementation ObjcMixedTargetWithPublicCXXAPIViaModuleImportTests
+@implementation ObjcMixedTargetWithPublicCXXAPITestsViaModuleImport
 
 - (void)testPublicObjcAPI {
     XCTAssertEqual([ObjcCalculator factorialForInt:5], 120);