Teach target_* commands to set INTERFACE properties of IMPORTED targets

Now, several `INTERFACE_*` properties can be set on `IMPORTED` targets,
not only via `set_property` and `set_target_properties` but also via
`target_compile_definitions`, `target_compile_features`,
`target_compile_options`, `target_include_directories`, `target_sources`
and `target_link_libraries`.

Fixes: #15689
Issue: #17197

Help/command/target_compile_definitions.rst

@@ -12,14 +12,15 @@ Add compile definitions to a target.
 Specify compile definitions to use when compiling a given ``<target>``.  The
 named ``<target>`` must have been created by a command such as
 :command:`add_executable` or :command:`add_library` and must not be an
-:ref:`Imported Target <Imported Targets>`.
+:ref:`ALIAS target <Alias Targets>`.
 
 The ``INTERFACE``, ``PUBLIC`` and ``PRIVATE`` keywords are required to
 specify the scope of the following arguments.  ``PRIVATE`` and ``PUBLIC``
 items will populate the :prop_tgt:`COMPILE_DEFINITIONS` property of
 ``<target>``. ``PUBLIC`` and ``INTERFACE`` items will populate the
-:prop_tgt:`INTERFACE_COMPILE_DEFINITIONS` property of ``<target>``.  The
-following arguments specify compile definitions.  Repeated calls for the
+:prop_tgt:`INTERFACE_COMPILE_DEFINITIONS` property of ``<target>``.
+(:ref:`IMPORTED targets <Imported Targets>` only support ``INTERFACE`` items.)
+The following arguments specify compile definitions.  Repeated calls for the
 same ``<target>`` append items in the order called.
 
 Arguments to ``target_compile_definitions`` may use "generator expressions"

Help/command/target_compile_features.rst

@@ -18,12 +18,13 @@ The ``INTERFACE``, ``PUBLIC`` and ``PRIVATE`` keywords are required to
 specify the scope of the features.  ``PRIVATE`` and ``PUBLIC`` items will
 populate the :prop_tgt:`COMPILE_FEATURES` property of ``<target>``.
 ``PUBLIC`` and ``INTERFACE`` items will populate the
-:prop_tgt:`INTERFACE_COMPILE_FEATURES` property of ``<target>``.  Repeated
-calls for the same ``<target>`` append items.
+:prop_tgt:`INTERFACE_COMPILE_FEATURES` property of ``<target>``.
+(:ref:`IMPORTED targets <Imported Targets>` only support ``INTERFACE`` items.)
+Repeated calls for the same ``<target>`` append items.
 
 The named ``<target>`` must have been created by a command such as
-:command:`add_executable` or :command:`add_library` and must not be
-an ``IMPORTED`` target.
+:command:`add_executable` or :command:`add_library` and must not be an
+:ref:`ALIAS target <Alias Targets>`.
 
 Arguments to ``target_compile_features`` may use "generator expressions"
 with the syntax ``$<...>``.

Help/command/target_compile_options.rst

@@ -12,8 +12,10 @@ Add compile options to a target.
 Specify compile options to use when compiling a given target.  The
 named ``<target>`` must have been created by a command such as
 :command:`add_executable` or :command:`add_library` and must not be an
-:ref:`IMPORTED Target <Imported Targets>`.  If ``BEFORE`` is specified,
-the content will be prepended to the property instead of being appended.
+:ref:`ALIAS target <Alias Targets>`.
+
+If ``BEFORE`` is specified, the content will be prepended to the property
+instead of being appended.
 
 This command can be used to add any options, but
 alternative commands exist to add preprocessor definitions
@@ -27,8 +29,9 @@ The ``INTERFACE``, ``PUBLIC`` and ``PRIVATE`` keywords are required to
 specify the scope of the following arguments.  ``PRIVATE`` and ``PUBLIC``
 items will populate the :prop_tgt:`COMPILE_OPTIONS` property of
 ``<target>``.  ``PUBLIC`` and ``INTERFACE`` items will populate the
-:prop_tgt:`INTERFACE_COMPILE_OPTIONS` property of ``<target>``.  The
-following arguments specify compile options.  Repeated calls for the same
+:prop_tgt:`INTERFACE_COMPILE_OPTIONS` property of ``<target>``.
+(:ref:`IMPORTED targets <Imported Targets>` only support ``INTERFACE`` items.)
+The following arguments specify compile options.  Repeated calls for the same
 ``<target>`` append items in the order called.
 
 Arguments to ``target_compile_options`` may use "generator expressions"

Help/command/target_include_directories.rst

@@ -12,7 +12,7 @@ Add include directories to a target.
 Specify include directories to use when compiling a given target.
 The named ``<target>`` must have been created by a command such
 as :command:`add_executable` or :command:`add_library` and must not be an
-:prop_tgt:`IMPORTED` target.
+:ref:`ALIAS target <Alias Targets>`.
 
 If ``BEFORE`` is specified, the content will be prepended to the property
 instead of being appended.
@@ -21,9 +21,9 @@ The ``INTERFACE``, ``PUBLIC`` and ``PRIVATE`` keywords are required to specify
 the scope of the following arguments.  ``PRIVATE`` and ``PUBLIC`` items will
 populate the :prop_tgt:`INCLUDE_DIRECTORIES` property of ``<target>``.
 ``PUBLIC`` and ``INTERFACE`` items will populate the
-:prop_tgt:`INTERFACE_INCLUDE_DIRECTORIES`
-property of ``<target>``.  The following arguments specify include
-directories.
+:prop_tgt:`INTERFACE_INCLUDE_DIRECTORIES` property of ``<target>``.
+(:ref:`IMPORTED targets <Imported Targets>` only support ``INTERFACE`` items.)
+The following arguments specify include directories.
 
 Specified include directories may be absolute paths or relative paths.
 Repeated calls for the same <target> append items in the order called.  If

Help/command/target_link_libraries.rst

@@ -19,7 +19,8 @@ All of them have the general form::
   target_link_libraries(<target> ... <item>... ...)
 
 The named ``<target>`` must have been created in the current directory by
-a command such as :command:`add_executable` or :command:`add_library`.
+a command such as :command:`add_executable` or :command:`add_library` and
+must not be an :ref:`ALIAS target <Alias Targets>`.
 Repeated calls for the same ``<target>`` append items in the order called.
 Each ``<item>`` may be:
 

Help/command/target_sources.rst

@@ -12,14 +12,15 @@ Add sources to a target.
 Specify sources to use when compiling a given target.  The
 named ``<target>`` must have been created by a command such as
 :command:`add_executable` or :command:`add_library` and must not be an
-:ref:`IMPORTED Target <Imported Targets>`.
+:ref:`ALIAS target <Alias Targets>`.
 
 The ``INTERFACE``, ``PUBLIC`` and ``PRIVATE`` keywords are required to
 specify the scope of the following arguments.  ``PRIVATE`` and ``PUBLIC``
 items will populate the :prop_tgt:`SOURCES` property of
 ``<target>``.  ``PUBLIC`` and ``INTERFACE`` items will populate the
-:prop_tgt:`INTERFACE_SOURCES` property of ``<target>``.  The
-following arguments specify sources.  Repeated calls for the same
+:prop_tgt:`INTERFACE_SOURCES` property of ``<target>``.
+(:ref:`IMPORTED targets <Imported Targets>` only support ``INTERFACE`` items.)
+The following arguments specify sources.  Repeated calls for the same
 ``<target>`` append items in the order called.
 
 Arguments to ``target_sources`` may use "generator expressions"

Source/cmTargetCompileDefinitionsCommand.cxx

@@ -17,15 +17,6 @@ bool cmTargetCompileDefinitionsCommand::InitialPass(
   return this->HandleArguments(args, "COMPILE_DEFINITIONS");
 }
 
-void cmTargetCompileDefinitionsCommand::HandleImportedTarget(
-  const std::string& tgt)
-{
-  std::ostringstream e;
-  e << "Cannot specify compile definitions for imported target \"" << tgt
-    << "\".";
-  this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
-}
-
 void cmTargetCompileDefinitionsCommand::HandleMissingTarget(
   const std::string& name)
 {
@@ -56,5 +47,5 @@ bool cmTargetCompileDefinitionsCommand::HandleDirectContent(
   cmTarget* tgt, const std::vector<std::string>& content, bool, bool)
 {
   tgt->AppendProperty("COMPILE_DEFINITIONS", this->Join(content).c_str());
-  return true;
+  return true; // Successfully handled.
 }

Source/cmTargetCompileDefinitionsCommand.h

@@ -30,7 +30,6 @@ public:
                    cmExecutionStatus& status) override;
 
 private:
-  void HandleImportedTarget(const std::string& tgt) override;
   void HandleMissingTarget(const std::string& name) override;
 
   bool HandleDirectContent(cmTarget* tgt,

Source/cmTargetCompileFeaturesCommand.cxx

@@ -17,15 +17,6 @@ bool cmTargetCompileFeaturesCommand::InitialPass(
   return this->HandleArguments(args, "COMPILE_FEATURES", NO_FLAGS);
 }
 
-void cmTargetCompileFeaturesCommand::HandleImportedTarget(
-  const std::string& tgt)
-{
-  std::ostringstream e;
-  e << "Cannot specify compile features for imported target \"" << tgt
-    << "\".";
-  this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
-}
-
 void cmTargetCompileFeaturesCommand::HandleMissingTarget(
   const std::string& name)
 {
@@ -49,8 +40,8 @@ bool cmTargetCompileFeaturesCommand::HandleDirectContent(
     std::string error;
     if (!this->Makefile->AddRequiredTargetFeature(tgt, it, &error)) {
       this->SetError(error);
-      return false;
+      return false; // Not (successfully) handled.
     }
   }
-  return true;
+  return true; // Successfully handled.
 }

Source/cmTargetCompileFeaturesCommand.h

@@ -22,7 +22,6 @@ class cmTargetCompileFeaturesCommand : public cmTargetPropCommandBase
                    cmExecutionStatus& status) override;
 
 private:
-  void HandleImportedTarget(const std::string& tgt) override;
   void HandleMissingTarget(const std::string& name) override;
 
   bool HandleDirectContent(cmTarget* tgt,

Source/cmTargetCompileOptionsCommand.cxx

@@ -18,21 +18,12 @@ bool cmTargetCompileOptionsCommand::InitialPass(
   return this->HandleArguments(args, "COMPILE_OPTIONS", PROCESS_BEFORE);
 }
 
-void cmTargetCompileOptionsCommand::HandleImportedTarget(
-  const std::string& tgt)
-{
-  std::ostringstream e;
-  e << "Cannot specify compile options for imported target \"" << tgt << "\".";
-  this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
-}
-
 void cmTargetCompileOptionsCommand::HandleMissingTarget(
   const std::string& name)
 {
   std::ostringstream e;
   e << "Cannot specify compile options for target \"" << name
-    << "\" "
-       "which is not built by this project.";
+    << "\" which is not built by this project.";
   this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
 }
 
@@ -47,5 +38,5 @@ bool cmTargetCompileOptionsCommand::HandleDirectContent(
 {
   cmListFileBacktrace lfbt = this->Makefile->GetBacktrace();
   tgt->InsertCompileOption(this->Join(content), lfbt);
-  return true;
+  return true; // Successfully handled.
 }

Source/cmTargetCompileOptionsCommand.h

@@ -30,7 +30,6 @@ public:
                    cmExecutionStatus& status) override;
 
 private:
-  void HandleImportedTarget(const std::string& tgt) override;
   void HandleMissingTarget(const std::string& name) override;
 
   bool HandleDirectContent(cmTarget* tgt,

Source/cmTargetIncludeDirectoriesCommand.cxx

@@ -21,22 +21,12 @@ bool cmTargetIncludeDirectoriesCommand::InitialPass(
                                ArgumentFlags(PROCESS_BEFORE | PROCESS_SYSTEM));
 }
 
-void cmTargetIncludeDirectoriesCommand::HandleImportedTarget(
-  const std::string& tgt)
-{
-  std::ostringstream e;
-  e << "Cannot specify include directories for imported target \"" << tgt
-    << "\".";
-  this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
-}
-
 void cmTargetIncludeDirectoriesCommand::HandleMissingTarget(
   const std::string& name)
 {
   std::ostringstream e;
   e << "Cannot specify include directories for target \"" << name
-    << "\" "
-       "which is not built by this project.";
+    << "\" which is not built by this project.";
   this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
 }
 
@@ -79,7 +69,7 @@ bool cmTargetIncludeDirectoriesCommand::HandleDirectContent(
     }
     tgt->AddSystemIncludeDirectories(sdirs);
   }
-  return true;
+  return true; // Successfully handled.
 }
 
 void cmTargetIncludeDirectoriesCommand::HandleInterfaceContent(

Source/cmTargetIncludeDirectoriesCommand.h

@@ -30,7 +30,6 @@ public:
                    cmExecutionStatus& status) override;
 
 private:
-  void HandleImportedTarget(const std::string& tgt) override;
   void HandleMissingTarget(const std::string& name) override;
 
   bool HandleDirectContent(cmTarget* tgt,

Source/cmTargetLinkLibrariesCommand.cxx

@@ -39,6 +39,16 @@ bool cmTargetLinkLibrariesCommand::InitialPass(
   this->Target =
     this->Makefile->GetCMakeInstance()->GetGlobalGenerator()->FindTarget(
       args[0]);
+  if (!this->Target) {
+    const std::vector<cmTarget*>& importedTargets =
+      this->Makefile->GetOwnedImportedTargets();
+    for (cmTarget* importedTarget : importedTargets) {
+      if (importedTarget->GetName() == args[0]) {
+        this->Target = importedTarget;
+        break;
+      }
+    }
+  }
   if (!this->Target) {
     cmake::MessageType t = cmake::FATAL_ERROR; // fail by default
     std::ostringstream e;
@@ -228,7 +238,7 @@ bool cmTargetLinkLibrariesCommand::InitialPass(
     } else {
       // Lookup old-style cache entry if type is unspecified.  So if you
       // do a target_link_libraries(foo optimized bar) it will stay optimized
-      // and not use the lookup.  As there maybe the case where someone has
+      // and not use the lookup.  As there may be the case where someone has
       // specifed that a library is both debug and optimized.  (this check is
       // only there for backwards compatibility when mixing projects built
       // with old versions of CMake and new)
@@ -299,6 +309,14 @@ bool cmTargetLinkLibrariesCommand::HandleLibrary(const std::string& lib,
       "target_link_libraries");
     return false;
   }
+  if (this->Target->IsImported() &&
+      this->CurrentProcessingState != ProcessingKeywordLinkInterface) {
+    this->Makefile->IssueMessage(
+      cmake::FATAL_ERROR,
+      "IMPORTED library can only be used with the INTERFACE keyword of "
+      "target_link_libraries");
+    return false;
+  }
 
   cmTarget::TLLSignature sig =
     (this->CurrentProcessingState == ProcessingPlainPrivateInterface ||
@@ -354,6 +372,16 @@ bool cmTargetLinkLibrariesCommand::HandleLibrary(const std::string& lib,
 
     cmTarget* t =
       this->Makefile->FindLocalNonAliasTarget(this->Target->GetName());
+    if (!t) {
+      const std::vector<cmTarget*>& importedTargets =
+        this->Makefile->GetOwnedImportedTargets();
+      for (cmTarget* importedTarget : importedTargets) {
+        if (importedTarget->GetName() == this->Target->GetName()) {
+          t = importedTarget;
+          break;
+        }
+      }
+    }
     if (!t) {
       std::ostringstream e;
       e << "Attempt to add link library \"" << lib << "\" to target \""

Source/cmTargetPropCommandBase.cxx

@@ -84,17 +84,15 @@ bool cmTargetPropCommandBase::ProcessContentArgs(
     this->SetError("called with invalid arguments");
     return false;
   }
-
-  if (this->Target->IsImported()) {
-    this->HandleImportedTarget(args[0]);
-    return false;
-  }
-
   if (this->Target->GetType() == cmStateEnums::INTERFACE_LIBRARY &&
       scope != "INTERFACE") {
     this->SetError("may only set INTERFACE properties on INTERFACE targets");
     return false;
   }
+  if (this->Target->IsImported() && scope != "INTERFACE") {
+    this->SetError("may only set INTERFACE properties on IMPORTED targets");
+    return false;
+  }
 
   ++argIndex;
 

Source/cmTargetPropCommandBase.h

@@ -35,7 +35,6 @@ protected:
                                       bool prepend, bool system);
 
 private:
-  virtual void HandleImportedTarget(const std::string& tgt) = 0;
   virtual void HandleMissingTarget(const std::string& name) = 0;
 
   virtual bool HandleDirectContent(cmTarget* tgt,

Source/cmTargetSourcesCommand.cxx

@@ -17,13 +17,6 @@ bool cmTargetSourcesCommand::InitialPass(std::vector<std::string> const& args,
   return this->HandleArguments(args, "SOURCES");
 }
 
-void cmTargetSourcesCommand::HandleImportedTarget(const std::string& tgt)
-{
-  std::ostringstream e;
-  e << "Cannot specify sources for imported target \"" << tgt << "\".";
-  this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
-}
-
 void cmTargetSourcesCommand::HandleMissingTarget(const std::string& name)
 {
   std::ostringstream e;
@@ -43,5 +36,5 @@ bool cmTargetSourcesCommand::HandleDirectContent(
   cmTarget* tgt, const std::vector<std::string>& content, bool, bool)
 {
   tgt->AppendProperty("SOURCES", this->Join(content).c_str());
-  return true;
+  return true; // Successfully handled.
 }

Source/cmTargetSourcesCommand.h

@@ -30,7 +30,6 @@ public:
                    cmExecutionStatus& status) override;
 
 private:
-  void HandleImportedTarget(const std::string& tgt) override;
   void HandleMissingTarget(const std::string& name) override;
 
   bool HandleDirectContent(cmTarget* tgt,

Tests/RunCMake/add_library/UNKNOWNwithNoSourcesButLinkObjects-stderr.txt

@@ -1,5 +0,0 @@
-^CMake Error at UNKNOWNwithNoSourcesButLinkObjects.cmake:[0-9]+ \(target_link_libraries\):
-  Cannot specify link libraries for target \"TestUnknownLibWithoutSources\"
-  which is not built by this project.
-Call Stack \(most recent call first\):
-  CMakeLists.txt:[0-9]+ \(include\)$

Tests/RunCMake/add_library/UNKNOWNwithNoSourcesButLinkObjects.cmake

@@ -2,4 +2,4 @@ enable_language(CXX)
 add_library(ObjectLibDependency OBJECT test.cpp)
 
 add_library(TestUnknownLibWithoutSources UNKNOWN IMPORTED)
-target_link_libraries(TestUnknownLibWithoutSources PUBLIC $<TARGET_OBJECTS:ObjectLibDependency>)
+target_link_libraries(TestUnknownLibWithoutSources INTERFACE $<TARGET_OBJECTS:ObjectLibDependency>)

Tests/RunCMake/target_compile_features/imported_target-stderr.txt

@@ -1,4 +1,5 @@
-CMake Error at imported_target.cmake:[0-9]+ \(target_compile_features\):
-  Cannot specify compile features for imported target "main".
+^CMake Error at imported_target.cmake:[0-9]+ \(target_compile_features\):
+  target_compile_features may only set INTERFACE properties on INTERFACE
+  targets
 Call Stack \(most recent call first\):
-  CMakeLists.txt:3 \(include\)
+  CMakeLists.txt:3 \(include\)$

Tests/RunCMake/target_compile_features/imported_target.cmake

@@ -1,4 +1,10 @@
 enable_language(CXX)
 
-add_library(main INTERFACE IMPORTED)
-target_compile_features(main INTERFACE cxx_delegating_constructors)
+add_library(lib1-interface INTERFACE IMPORTED)
+target_compile_features(lib1-interface INTERFACE cxx_delegating_constructors)
+
+add_library(lib2-interface INTERFACE IMPORTED)
+target_compile_features(lib2-interface PUBLIC cxx_delegating_constructors)
+
+add_library(lib-shared SHARED IMPORTED)
+target_compile_features(lib-shared INTERFACE cxx_delegating_constructors)

Tests/RunCMake/target_link_libraries/ImportedTarget.cmake

@@ -0,0 +1,2 @@
+add_library(UnknownImportedGlobal UNKNOWN IMPORTED GLOBAL)
+target_link_libraries(UnknownImportedGlobal INTERFACE z)

Tests/RunCMake/target_link_libraries/ImportedTargetFailure-stderr.txt

@@ -0,0 +1,5 @@
+^CMake Error at ImportedTargetFailure.cmake:[0-9]+ \(target_link_libraries\):
+  IMPORTED library can only be used with the INTERFACE keyword of
+  target_link_libraries
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:[0-9]+ \(include\)$

Tests/RunCMake/target_link_libraries/ImportedTargetFailure.cmake

@@ -0,0 +1,2 @@
+add_library(UnknownImportedGlobal UNKNOWN IMPORTED GLOBAL)
+target_link_libraries(UnknownImportedGlobal PRIVATE z)

Tests/RunCMake/target_link_libraries/RunCMakeTest.cmake

@@ -4,6 +4,8 @@ run_cmake(CMP0023-WARN)
 run_cmake(CMP0023-NEW)
 run_cmake(CMP0023-WARN-2)
 run_cmake(CMP0023-NEW-2)
+run_cmake(ImportedTarget)
+run_cmake(ImportedTargetFailure)
 run_cmake(MixedSignature)
 run_cmake(Separate-PRIVATE-LINK_PRIVATE-uses)
 run_cmake(SubDirTarget)