Swift: Use per-config module file locations in multi-config generators

Place `.swiftmodule` files a subdirectory named after the configuration.

Fixes: #25864
Fixes: #25997

- Swift/RunCMakeTest.cmake:
  - CMP0157-OLD was enabled for Xcode, where it works.
  - A test was added that verifies .swiftmodule's are generated into
    separate directories with multi-config generators.

- Tests/SwiftOnly/CMakeLists.txt: tests were added that validate that
  cross-subdirectory module dependencies (via target_link_libraries)
  work.

8 files changed, 30 insertions, 4 deletions

diff --git a/Tests/RunCMake/Swift/RunCMakeTest.cmake b/Tests/RunCMake/Swift/RunCMakeTest.cmake
index 39f754c..716075e 100644
--- a/Tests/RunCMake/Swift/RunCMakeTest.cmake
+++ b/Tests/RunCMake/Swift/RunCMakeTest.cmake
@@ -19,9 +19,7 @@ block()
   run_cmake(CMP0157-NEW)
   run_cmake(CMP0157-WARN)
 
-  if(RunCMake_GENERATOR MATCHES "Ninja.*")
-    set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/CMP0157-OLD-build)
-  endif()
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/CMP0157-OLD-build)
 
   run_cmake(CMP0157-OLD)
 
@@ -32,9 +30,25 @@ block()
   endif()
 endblock()
 
-if(RunCMake_GENERATOR MATCHES "Ninja")
+block()
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/SwiftSimple-build)
   run_cmake(SwiftSimple)
+  if(RunCMake_GENERATOR_IS_MULTI_CONFIG AND
+      # Older Xcode versions didn't support Swift static libraries.
+      NOT (RunCMake_GENERATOR STREQUAL "Xcode" AND XCODE_VERSION VERSION_LESS 9.0))
+    # Check that .swiftmodule files get their own directories
+    set(RunCMake_TEST_NO_CLEAN 1)
+    run_cmake_command(SwiftSimple-build-Debug ${CMAKE_COMMAND} --build . --config Debug)
+    run_cmake_command(SwiftSimple-build-Release ${CMAKE_COMMAND} --build . --config Release)
 
+    # Will fail if either path doesn't exist. Passing -r because Xcode
+    # generates .swiftmodule directories.
+    run_cmake_command(SwiftSimple-verify ${CMAKE_COMMAND} -E
+      rm -r Debug/L.swiftmodule Release/L.swiftmodule)
+  endif()
+endblock()
+
+if(RunCMake_GENERATOR MATCHES "Ninja")
   block()
     if (CMAKE_SYSTEM_NAME MATCHES "Windows")
       run_cmake_with_options(Win32ExecutableDisallowed)
diff --git a/Tests/SwiftOnly/CMakeLists.txt b/Tests/SwiftOnly/CMakeLists.txt
index 25892f1..e933ea1 100644
--- a/Tests/SwiftOnly/CMakeLists.txt
+++ b/Tests/SwiftOnly/CMakeLists.txt
@@ -28,6 +28,10 @@ endif()
 add_subdirectory(SubA)
 add_subdirectory(SubB)
 
+add_subdirectory(SubC)
+add_subdirectory(SubD)
+add_subdirectory(SubE)
+
 set(CMAKE_Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/swift)
 
 add_executable(SwiftOnly main.swift)
diff --git a/Tests/SwiftOnly/SubC/CMakeLists.txt b/Tests/SwiftOnly/SubC/CMakeLists.txt
new file mode 100644
index 0000000..4fdb3d3
--- /dev/null
+++ b/Tests/SwiftOnly/SubC/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_library(SubC SubC.swift)
+target_link_libraries(SubC PUBLIC SubD)
diff --git a/Tests/SwiftOnly/SubC/SubC.swift b/Tests/SwiftOnly/SubC/SubC.swift
new file mode 100644
index 0000000..1ca44f4
--- /dev/null
+++ b/Tests/SwiftOnly/SubC/SubC.swift
@@ -0,0 +1 @@
+import SubD
diff --git a/Tests/SwiftOnly/SubD/CMakeLists.txt b/Tests/SwiftOnly/SubD/CMakeLists.txt
new file mode 100644
index 0000000..01b38d3
--- /dev/null
+++ b/Tests/SwiftOnly/SubD/CMakeLists.txt
@@ -0,0 +1 @@
+add_library(SubD SubD.swift)
diff --git a/Tests/SwiftOnly/SubD/SubD.swift b/Tests/SwiftOnly/SubD/SubD.swift
new file mode 100644
index 0000000..857d3f4
--- /dev/null
+++ b/Tests/SwiftOnly/SubD/SubD.swift
@@ -0,0 +1 @@
+public let x = 42
diff --git a/Tests/SwiftOnly/SubE/CMakeLists.txt b/Tests/SwiftOnly/SubE/CMakeLists.txt
new file mode 100644
index 0000000..099a81c
--- /dev/null
+++ b/Tests/SwiftOnly/SubE/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_executable(SubE main.swift)
+target_link_libraries(SubE PUBLIC SubD)
diff --git a/Tests/SwiftOnly/SubE/main.swift b/Tests/SwiftOnly/SubE/main.swift
new file mode 100644
index 0000000..1ca44f4
--- /dev/null
+++ b/Tests/SwiftOnly/SubE/main.swift
@@ -0,0 +1 @@
+import SubD