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

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,