Export: Expand CPS default targets

CPS provides "default targets" as a user convenience which can be linked
by specifying only the package name. CMake implements this via a utility
`INTERFACE` target. However, because it is not namespaced, this is not a
valid requirement, which prevents exporting anything linking to this
target to CPS.

Work around this by introducing a new (internal) target property which
replaces a target with its link interface targets at export time.

Source/cmExportFileGenerator.cxx

@@ -398,6 +398,21 @@ bool cmExportFileGenerator::AddTargetNamespace(std::string& input,
     return false;
   }
 
+  std::vector<std::string> replace = tgt->Target->GetExportTargets();
+  if (!replace.empty()) {
+    std::vector<std::string> out;
+    out.reserve(replace.size());
+
+    bool result = true;
+    for (std::string& t : replace) {
+      result = this->AddTargetNamespace(t, target, lg) && result;
+      out.emplace_back(std::move(t));
+    }
+
+    input = cmJoin(out, ";"_s);
+    return result;
+  }
+
   cmFindPackageStack const& pkgStack = tgt->Target->GetFindPackageStack();
   if (!pkgStack.Empty() ||
       tgt->Target->GetProperty("EXPORT_FIND_PACKAGE_NAME")) {

Source/cmPackageInfoReader.cxx

@@ -1005,6 +1005,7 @@ bool cmPackageInfoReader::ImportTargets(cmMakefile* makefile,
       std::string const& fullName = cmStrCat(package, "::"_s, name);
       AppendProperty(makefile, target, "LINK_LIBRARIES"_s, {}, fullName);
     }
+    target->SetExportPassthrough(true);
   }
 
   return true;

Source/cmTarget.cxx

@@ -631,6 +631,7 @@ public:
   bool PerConfig = false;
   bool IsSymbolic = false;
   bool IsForTryCompile = false;
+  bool IsExportPassthrough = false;
   cmTarget::Visibility TargetVisibility;
   std::set<BT<std::pair<std::string, bool>>> Utilities;
   std::set<std::string> CodegenDependencies;
@@ -2150,6 +2151,12 @@ void cmTarget::SetSymbolic(bool const value)
   this->impl->IsSymbolic = value;
 }
 
+void cmTarget::SetExportPassthrough(bool value)
+{
+  assert(this->impl->TargetType == cm::TargetType::INTERFACE_LIBRARY);
+  this->impl->IsExportPassthrough = value;
+}
+
 void cmTarget::SetProperty(std::string const& prop, cmValue value)
 {
   if (!IsSettableProperty(this->impl->Makefile, this, prop)) {
@@ -3007,6 +3014,14 @@ bool cmTarget::IsForTryCompile() const
   return this->impl->IsForTryCompile;
 }
 
+std::vector<std::string> cmTarget::GetExportTargets() const
+{
+  if (this->impl->IsExportPassthrough) {
+    return cm::remove_BT(this->impl->InterfaceLinkLibraries.Entries);
+  }
+  return {};
+}
+
 char const* cmTarget::GetSuffixVariableInternal(
   cmStateEnums::ArtifactType artifact) const
 {

Source/cmTarget.h

@@ -210,6 +210,8 @@ public:
 
   void SetSymbolic(bool value);
 
+  void SetExportPassthrough(bool value);
+
   //! Set/Get a property of this target file
   void SetProperty(std::string const& prop, cmValue value);
   void SetProperty(std::string const& prop, std::nullptr_t)
@@ -254,6 +256,13 @@ public:
   void SetIsForTryCompile();
   bool IsForTryCompile() const;
 
+  /**
+   * Get the list of targets which should replace this target on export. This
+   * equals the target's interface link libraries iff the target is an export
+   * passthrough target. For all other targets, this returns an empty list.
+   */
+  std::vector<std::string> GetExportTargets() const;
+
   bool GetMappedConfig(std::string const& desiredConfig, cmValue& loc,
                        cmValue& imp, std::string& suffix) const;
 

Tests/RunCMake/CMakeLists.txt

@@ -1515,6 +1515,7 @@ add_RunCMake_test(AutoExportDll
   )
 
 add_RunCMake_test(AndroidMK)
+add_RunCMake_test(ExportCpsDefaultComponents)
 add_RunCMake_test(ExportPackageInfo)
 add_RunCMake_test(ExportSbom)
 add_RunCMake_test(EnvSbom)

Tests/RunCMake/ExportCpsDefaultComponents/Assertions.cmake

@@ -0,0 +1,39 @@
+macro(_expect entity op actual expected)
+  if(NOT "${actual}" ${op} "${expected}")
+    list(JOIN ARGN "." name)
+    set(RunCMake_TEST_FAILED
+      "Attribute '${name}' ${entity} '${actual}' does not match expected ${entity} '${expected}'" PARENT_SCOPE)
+    return()
+  endif()
+endmacro()
+
+function(expect_value content expected_value)
+  string(JSON actual_value GET "${content}" ${ARGN})
+  _expect("value" STREQUAL "${actual_value}" "${expected_value}" ${ARGN})
+endfunction()
+
+function(expect_array content expected_length)
+  string(JSON actual_type TYPE "${content}" ${ARGN})
+  _expect("type" STREQUAL "${actual_type}" "ARRAY" ${ARGN})
+
+  string(JSON actual_length LENGTH "${content}" ${ARGN})
+  _expect("length" EQUAL "${actual_length}" "${expected_length}" ${ARGN})
+endfunction()
+
+function(expect_object content)
+  string(JSON actual_type TYPE "${content}" ${ARGN})
+  _expect("type" STREQUAL "${actual_type}" "OBJECT" ${ARGN})
+endfunction()
+
+function(expect_null content)
+  string(JSON actual_type TYPE "${content}" ${ARGN})
+  _expect("type" STREQUAL "${actual_type}" "NULL" ${ARGN})
+endfunction()
+
+function(expect_missing content)
+  string(JSON value ERROR_VARIABLE error GET "${content}" ${ARGN})
+  if(NOT value MATCHES "^(.*-)?NOTFOUND$")
+    set(RunCMake_TEST_FAILED
+      "Attribute '${ARGN}' is unexpectedly present" PARENT_SCOPE)
+  endif()
+endfunction()

Tests/RunCMake/ExportCpsDefaultComponents/CMakeLists.txt

@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 4.4.0)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)

Tests/RunCMake/ExportCpsDefaultComponents/GenExExportCMake-check.cmake

@@ -0,0 +1,13 @@
+include(${CMAKE_CURRENT_LIST_DIR}/Assertions.cmake)
+
+set(out_dir "${RunCMake_BINARY_DIR}/GenExExportCMake-build")
+
+file(READ "${out_dir}/bar.cmake" bar_cmake)
+if(NOT "${bar_cmake}" MATCHES "add_library\\(bar INTERFACE IMPORTED\\)")
+  string(APPEND RunCMake_TEST_FAILED
+    "Interface library 'bar' was not exported\n")
+endif()
+if(NOT "${bar_cmake}" MATCHES "set_target_properties\\(bar PROPERTIES[ \n]+INTERFACE_LINK_LIBRARIES \"[\\][\$]<1:foo>\"[ \n]*\\)")
+  string(APPEND RunCMake_TEST_FAILED
+    "Interface library 'bar' has wrong link libraries\n")
+endif()

Tests/RunCMake/ExportCpsDefaultComponents/GenExExportCMake.cmake

@@ -0,0 +1,11 @@
+find_package(
+  foo REQUIRED CONFIG
+  NO_DEFAULT_PATH
+  PATHS ${CMAKE_CURRENT_LIST_DIR}
+  )
+
+add_library(bar INTERFACE)
+target_link_libraries(bar INTERFACE $<1:foo>)
+
+install(TARGETS bar EXPORT bar)
+export(EXPORT bar)

Tests/RunCMake/ExportCpsDefaultComponents/GenExExportCps-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/ExportCpsDefaultComponents/GenExExportCps-stderr.txt

@@ -0,0 +1,5 @@
+CMake Error in CMakeLists\.txt:
+  Property "INTERFACE_LINK_LIBRARIES" of target "bar" contains a generator
+  expression\.  This is not allowed\.[
+]+
+CMake Generate step failed\.  Build files cannot be regenerated correctly\.

Tests/RunCMake/ExportCpsDefaultComponents/GenExExportCps.cmake

@@ -0,0 +1,11 @@
+find_package(
+  foo REQUIRED CONFIG
+  NO_DEFAULT_PATH
+  PATHS ${CMAKE_CURRENT_LIST_DIR}
+  )
+
+add_library(bar INTERFACE)
+target_link_libraries(bar INTERFACE $<1:foo>)
+
+install(TARGETS bar EXPORT bar)
+export(PACKAGE_INFO bar EXPORT bar)

Tests/RunCMake/ExportCpsDefaultComponents/NormalExport-check.cmake

@@ -0,0 +1,27 @@
+include(${CMAKE_CURRENT_LIST_DIR}/Assertions.cmake)
+
+set(out_dir "${RunCMake_BINARY_DIR}/NormalExport-build")
+
+file(READ "${out_dir}/cps/bar/bar.cps" content)
+expect_value("${content}" "bar" "name")
+expect_value("${content}" "interface" "components" "bar" "type")
+
+expect_value("${content}" "bar" "name")
+expect_array("${content}"      2 "requires"  "foo" "components")
+expect_value("${content}" "foo1" "requires"  "foo" "components" 0)
+expect_value("${content}" "foo2" "requires"  "foo" "components" 1)
+
+string(JSON component GET "${content}" "components" "bar")
+expect_array("${component}" 2 "requires")
+expect_value("${component}" "foo:foo1" "requires" 0)
+expect_value("${component}" "foo:foo2" "requires" 1)
+
+file(READ "${out_dir}/bar.cmake" bar_cmake)
+if(NOT "${bar_cmake}" MATCHES "add_library\\(bar INTERFACE IMPORTED\\)")
+  string(APPEND RunCMake_TEST_FAILED
+    "Interface library 'bar' was not exported\n")
+endif()
+if(NOT "${bar_cmake}" MATCHES "set_target_properties\\(bar PROPERTIES[ \n]+INTERFACE_LINK_LIBRARIES \"foo::foo1;foo::foo2\"[ \n]*\\)")
+  string(APPEND RunCMake_TEST_FAILED
+    "Interface library 'bar' has wrong link libraries\n")
+endif()

Tests/RunCMake/ExportCpsDefaultComponents/NormalExport.cmake

@@ -0,0 +1,12 @@
+find_package(
+  foo REQUIRED CONFIG
+  NO_DEFAULT_PATH
+  PATHS ${CMAKE_CURRENT_LIST_DIR}
+  )
+
+add_library(bar INTERFACE)
+target_link_libraries(bar INTERFACE foo)
+
+install(TARGETS bar EXPORT bar)
+export(EXPORT bar)
+export(PACKAGE_INFO bar EXPORT bar)

Tests/RunCMake/ExportCpsDefaultComponents/RunCMakeTest.cmake

@@ -0,0 +1,8 @@
+include(RunCMake)
+
+# Test normal usage
+run_cmake(NormalExport)
+
+# Test usage via generator expression
+run_cmake(GenExExportCMake)
+run_cmake(GenExExportCps)

Tests/RunCMake/ExportCpsDefaultComponents/cps/foo.cps

@@ -0,0 +1,17 @@
+{
+  "cps_version" : "0.13.0",
+  "name" : "foo",
+  "cps_path" : "@prefix@/cps",
+  "default_components" : [ "foo1", "foo2" ],
+  "components" :
+  {
+    "foo1" :
+    {
+      "type" : "interface"
+    },
+    "foo2" :
+    {
+      "type" : "interface"
+    }
+  }
+}