Swift: Build with a package name by default

Add policy CMP0216 to enable use of the `PROJECT_NAME` as the default
package name for Swift.

Issue: #26886

Help/manual/cmake-policies.7.rst

@@ -100,6 +100,7 @@ Policies Introduced by CMake 4.4
 .. toctree::
    :maxdepth: 1
 
+   CMP0216: Swift targets have a default project name. </policy/CMP0216>
    CMP0215: Ninja generators emit Swift modules separately from compilation. </policy/CMP0215>
    CMP0214: Honor CMAKE_EXE_LINKER_FLAGS for Swift executable targets. </policy/CMP0214>
    CMP0213: file(ARCHIVE_{CREATE,EXTRACT}) encode archive paths as UTF-8 by default. </policy/CMP0213>

Help/policy/CMP0216.rst

@@ -0,0 +1,32 @@
+CMP0216
+-------
+
+.. versionadded:: 4.4
+
+Swift targets have a default project name.
+
+CMake 4.3 and below did not compile Swift targets with ``-package-name``.
+The package name is useful because Swift package access control makes types,
+functions, and properties visible to other libraries within the same package,
+but not from sources outside of the package.  CMake 4.4 and above prefer to
+pass ``-package-name`` by default using the :variable:`PROJECT_NAME` variable
+value.  This policy provides compatibility for projects that have not been
+updated to expect a package name.
+
+.. note::
+
+   Package access control was added in Swift 5.8 and Xcode 15. This policy has
+   no effect when using an earlier version of Swift or Xcode.
+
+The ``OLD`` behavior for this policy is to build Swift source files without
+passing a package-name.  The ``NEW`` behavior for this policy is to build
+Swift source files with a default package name from :variable:`PROJECT_NAME`.
+
+Regardless of whether this policy is set, the :prop_tgt:`Swift_PACKAGE_NAME`
+target property may be set to explicitly specify or suppress a package name.
+
+.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 4.4
+.. |WARNS_OR_DOES_NOT_WARN| replace:: does *not* warn
+.. include:: include/STANDARD_ADVICE.rst
+
+.. include:: include/DEPRECATED.rst

Help/prop_tgt/Swift_PACKAGE_NAME.rst

@@ -14,5 +14,8 @@ code.
    Package access control was added in Swift 5.8 and Xcode 15. This target
    property has no effect when using an earlier version of Swift or Xcode.
 
+If the property is not set, the :variable:`PROJECT_NAME` variable is used
+as the default package name.  See policy :policy:`CMP0216`.
+
 Setting this property to the empty string will result in the target being
 compiled without a package name.

Help/release/dev/swift-package-name.rst

@@ -1,5 +1,8 @@
 swift-package-name
 ------------------
 
+* Swift targets now have a package name by default.
+  See policy :policy:`CMP0216`.
+
 * The :prop_tgt:`Swift_PACKAGE_NAME` target property was added to
   specify a Swift package name.

Source/cmGeneratorTarget.cxx

@@ -6204,6 +6204,8 @@ std::string cmGeneratorTarget::GetSwiftPackageName() const
   std::string packageName;
   if (cmValue projectName = this->GetProperty("Swift_PACKAGE_NAME")) {
     packageName = *projectName;
+  } else if (this->GetPolicyStatusCMP0216() == cmPolicies::NEW) {
+    packageName = this->Makefile->GetSafeDefinition("PROJECT_NAME");
   }
   return packageName;
 }

Source/cmPolicies.h

@@ -645,7 +645,9 @@ class cmMakefile;
          0, WARN)                                                             \
   SELECT(POLICY, CMP0215,                                                     \
          "Ninja generators emit Swift modules separately from compilation.",  \
-         4, 4, 0, WARN)
+         4, 4, 0, WARN)                                                       \
+  SELECT(POLICY, CMP0216, "Swift targets have a default project name.", 4, 4, \
+         0, WARN)
 
 #define CM_SELECT_ID(F, A1, A2, A3, A4, A5, A6) F(A1)
 #define CM_FOR_EACH_POLICY_ID(POLICY)                                         \
@@ -703,7 +705,8 @@ class cmMakefile;
   F(CMP0210)                                                                  \
   F(CMP0211)                                                                  \
   F(CMP0214)                                                                  \
-  F(CMP0215)
+  F(CMP0215)                                                                  \
+  F(CMP0216)
 
 #define CM_FOR_EACH_CUSTOM_COMMAND_POLICY(F)                                  \
   F(CMP0116)                                                                  \

Tests/RunCMake/Swift/CMP0216-NEW-check.cmake

@@ -0,0 +1,21 @@
+if(RunCMake_GENERATOR MATCHES "Ninja")
+  if(RunCMake_GENERATOR_IS_MULTI_CONFIG)
+    set(path "${RunCMake_TEST_BINARY_DIR}/CMakeFiles/impl-Debug.ninja")
+  else()
+    set(path "${RunCMake_TEST_BINARY_DIR}/build.ninja")
+  endif()
+  file(READ "${path}" build_ninja)
+
+  if(NOT build_ninja MATCHES "-package-name")
+    set(RunCMake_TEST_FAILED
+      "Expected -package-name in generated Ninja build files when CMP0216 is NEW")
+  endif()
+elseif(RunCMake_GENERATOR MATCHES "Xcode")
+  file(READ
+    "${RunCMake_TEST_BINARY_DIR}/CMP0216-NEW.xcodeproj/project.pbxproj"
+    pbxproj)
+  if(NOT pbxproj MATCHES "SWIFT_PACKAGE_NAME")
+    set(RunCMake_TEST_FAILED
+      "Expected SWIFT_PACKAGE_NAME in generated Xcode project when CMP0216 is NEW")
+  endif()
+endif()

Tests/RunCMake/Swift/CMP0216-NEW.cmake

@@ -0,0 +1,4 @@
+cmake_minimum_required(VERSION 4.0)
+
+cmake_policy(SET CMP0216 NEW)
+include(CMP0216-common.cmake)

Tests/RunCMake/Swift/CMP0216-OLD-check.cmake

@@ -0,0 +1,20 @@
+if(RunCMake_GENERATOR MATCHES "Ninja")
+  if(RunCMake_GENERATOR_IS_MULTI_CONFIG)
+    set(path "${RunCMake_TEST_BINARY_DIR}/CMakeFiles/impl-Debug.ninja")
+  else()
+    set(path "${RunCMake_TEST_BINARY_DIR}/build.ninja")
+  endif()
+  file(READ "${path}" build_ninja)
+  if(_content MATCHES "-package-name")
+    set(RunCMake_TEST_FAILED
+      "Unexpected -package-name in generated Ninja build files when CMP0216 is OLD")
+  endif()
+elseif(RunCMake_GENERATOR MATCHES "Xcode")
+  file(READ
+    "${RunCMake_TEST_BINARY_DIR}/CMP0216-OLD.xcodeproj/project.pbxproj"
+    pbxproj)
+  if(pbxproj MATCHES "SWIFT_PACKAGE_NAME")
+    set(RunCMake_TEST_FAILED
+      "Unexpected SWIFT_PACKAGE_NAME in generated Xcode project when CMP0216 is OLD")
+  endif()
+endif()

Tests/RunCMake/Swift/CMP0216-OLD.cmake

@@ -0,0 +1,4 @@
+cmake_minimum_required(VERSION 4.0)
+
+cmake_policy(SET CMP0216 OLD)
+include(CMP0216-common.cmake)

Tests/RunCMake/Swift/CMP0216-common.cmake

@@ -0,0 +1,3 @@
+enable_language(Swift)
+
+add_library(L STATIC L.swift)

Tests/RunCMake/Swift/CompileCommands.cmake

@@ -4,6 +4,7 @@ endif()
 if(POLICY CMP0195)
   cmake_policy(SET CMP0195 NEW)
 endif()
+cmake_policy(SET CMP0216 NEW)
 
 set(CMAKE_Swift_COMPILATION_MODE "singlefile")
 

Tests/RunCMake/Swift/MultiLangChain.cmake

@@ -1,5 +1,6 @@
 cmake_policy(SET CMP0157 NEW)
 cmake_policy(SET CMP0195 NEW)
+cmake_policy(SET CMP0216 NEW)
 
 enable_language(Swift C)
 

Tests/RunCMake/Swift/RunCMakeTest.cmake

@@ -186,4 +186,6 @@ endif()
 if(NOT RunCMake_GENERATOR STREQUAL "Xcode" OR
     (RunCMake_GENERATOR STREQUAL "Xcode" AND XCODE_VERSION VERSION_GREATER_EQUAL 15.0))
   run_cmake(PackageName)
+  run_cmake(CMP0216-OLD)
+  run_cmake(CMP0216-NEW)
 endif()

Tests/RunCMake/TargetPolicies/PolicyList-stderr.txt

@@ -57,6 +57,7 @@
    \* CMP0211
    \* CMP0214
    \* CMP0215
+   \* CMP0216
 
 Call Stack \(most recent call first\):
   CMakeLists\.txt:3 \(include\)