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.

Source/cmGeneratorTarget.h

@@ -544,6 +544,12 @@ public:
       the given configuration.  */
   std::string GetSwiftModulePath(std::string const& config) const;
 
+  /** Return the directory containing Swift module interface
+      descriptions for this target (including its `.swiftmodule`,
+      `.abi.json`, and `.swiftdoc`) in the given configuration.  */
+  std::string GetSwiftModuleDirectory(std::string const& config) const;
+
+private:
   /** Return the given property of this target if it exists; otherwise
       return defaultValue. */
   std::string GetPropertyOrDefault(std::string const& property,
@@ -552,12 +558,6 @@ public:
   /** Return the name of the `.swiftmodule` file for this target. */
   std::string GetSwiftModuleFileName() const;
 
-private:
-  /** Return the directory containing Swift module interface
-      descriptions for this target (including its `.swiftmodule`,
-      `.abi.json`, and `.swiftdoc`) in the given configuration.  */
-  std::string GetSwiftModuleDirectory(std::string const& config) const;
-
   using ConfigAndLanguage = std::pair<std::string, std::string>;
   using ConfigAndLanguageToBTStrings =
     std::map<ConfigAndLanguage, std::vector<BT<std::string>>>;

Source/cmGeneratorTarget_IncludeDirectories.cxx

@@ -114,7 +114,10 @@ void AddLangSpecificImplicitIncludeDirectories(
           auto* lg = dependency->GetLocalGenerator();
           EvaluatedTargetPropertyEntry entry{ library, library.Backtrace };
 
-          if (cmValue val = dependency->GetProperty(propertyName)) {
+          if (lang == "Swift") {
+            entry.Values.emplace_back(
+              dependency->GetSwiftModuleDirectory(config));
+          } else if (cmValue val = dependency->GetProperty(propertyName)) {
             entry.Values.emplace_back(*val);
           } else {
             if (mode == IncludeDirectoryFallBack::BINARY) {

Source/cmNinjaNormalTargetGenerator.cxx

@@ -1078,19 +1078,6 @@ void cmNinjaNormalTargetGenerator::WriteNvidiaDeviceLinkStatement(
   this->WriteNvidiaDeviceLinkRule(usedResponseFile, config);
 }
 
-/// Compute the swift module path for the target, sans any config-specific
-/// subdirectory.
-/// The returned path will need to be converted to the generator path
-static std::string GetSwiftModulePathTree(cmGeneratorTarget const* target)
-{
-  std::string moduleName = target->GetSwiftModuleName();
-  std::string moduleDirectory = target->GetPropertyOrDefault(
-    "Swift_MODULE_DIRECTORY",
-    target->LocalGenerator->GetCurrentBinaryDirectory());
-  std::string moduleFileName = target->GetSwiftModuleFileName();
-  return moduleDirectory + "/" + moduleFileName;
-}
-
 void cmNinjaNormalTargetGenerator::WriteLinkStatement(
   const std::string& config, const std::string& fileConfig,
   bool firstForConfig)
@@ -1205,7 +1192,7 @@ void cmNinjaNormalTargetGenerator::WriteLinkStatement(
 
     vars["SWIFT_MODULE_NAME"] = gt->GetSwiftModuleName();
     vars["SWIFT_MODULE"] = this->GetLocalGenerator()->ConvertToOutputFormat(
-      this->ConvertToNinjaPath(GetSwiftModulePathTree(gt)),
+      this->ConvertToNinjaPath(gt->GetSwiftModulePath(config)),
       cmOutputConverter::SHELL);
 
     vars["SWIFT_SOURCES"] = [this, config]() -> std::string {
@@ -1538,7 +1525,7 @@ void cmNinjaNormalTargetGenerator::WriteLinkStatement(
         if (dependency.Target &&
             dependency.Target->GetLinkerLanguage(config) == "Swift") {
           std::string swiftmodule = this->ConvertToNinjaPath(
-            GetSwiftModulePathTree(dependency.Target));
+            dependency.Target->GetSwiftModulePath(config));
           linkBuild.ImplicitDeps.emplace_back(swiftmodule);
         }
       }

Source/cmNinjaTargetGenerator.cxx

@@ -1961,15 +1961,9 @@ void cmNinjaTargetGenerator::WriteSwiftObjectBuildStatement(
   // changes to input files (e.g. addition of a comment).
   vars.emplace("restat", "1");
 
-  std::string const moduleName =
-    target.GetPropertyOrDefault("Swift_MODULE_NAME", target.GetName());
-  std::string const moduleDirectory = target.GetPropertyOrDefault(
-    "Swift_MODULE_DIRECTORY",
-    target.LocalGenerator->GetCurrentBinaryDirectory());
-  std::string const moduleFilename = target.GetPropertyOrDefault(
-    "Swift_MODULE", cmStrCat(moduleName, ".swiftmodule"));
+  std::string const moduleName = target.GetSwiftModuleName();
   std::string const moduleFilepath =
-    this->ConvertToNinjaPath(cmStrCat(moduleDirectory, '/', moduleFilename));
+    this->ConvertToNinjaPath(target.GetSwiftModulePath(config));
 
   vars.emplace("description",
                cmStrCat("Building Swift Module '", moduleName, "' with ",
@@ -2087,15 +2081,8 @@ void cmNinjaTargetGenerator::WriteSwiftObjectBuildStatement(
     // If the dependency emits a swiftmodule, add a dependency edge on that
     // swiftmodule to the ninja build graph.
     if (isImportableTarget(*dep)) {
-      std::string const depModuleName =
-        dep->GetPropertyOrDefault("Swift_MODULE_NAME", dep->GetName());
-      std::string const depModuleDir = dep->GetPropertyOrDefault(
-        "Swift_MODULE_DIRECTORY",
-        dep->LocalGenerator->GetCurrentBinaryDirectory());
-      std::string const depModuleFilename = dep->GetPropertyOrDefault(
-        "Swift_MODULE", cmStrCat(depModuleName, ".swiftmodule"));
-      std::string const depModuleFilepath = this->ConvertToNinjaPath(
-        cmStrCat(depModuleDir, '/', depModuleFilename));
+      std::string const depModuleFilepath =
+        this->ConvertToNinjaPath(dep->GetSwiftModulePath(config));
       objBuild.ImplicitDeps.push_back(depModuleFilepath);
     }
   }