cmTarget: Move sanity checks and computed property access to callers

The GetProperty method is now just accessing contained data, meaning it
can be implemented in cmState.

Remove the cmMakefile context from the signature as a result and remove
the overload with the same signature.

Add a GetComputedProperty to cmTarget so that templates can be properly
instantiated.  Otherwise the Commands would need to be able to reach the
specializations which are currently in cmTarget.cxx.

As a side-effect, the CMP0026 warning now gives a backtrace to the
target when issued from a generator expression.

5 files changed, 45 insertions, 22 deletions

diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 050fcb8..b0ff13e 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -397,6 +397,18 @@ std::string cmGeneratorTarget::GetExportName() const
 
 const char* cmGeneratorTarget::GetProperty(const std::string& prop) const
 {
+  if (!cmTargetPropertyComputer::PassesWhitelist(
+        this->GetType(), prop, this->Makefile->GetMessenger(),
+        this->GetBacktrace())) {
+    return 0;
+  }
+  if (const char* result = cmTargetPropertyComputer::GetProperty(
+        this, prop, this->Makefile->GetMessenger(), this->GetBacktrace())) {
+    return result;
+  }
+  if (cmSystemTools::GetFatalErrorOccured()) {
+    return CM_NULLPTR;
+  }
   return this->Target->GetProperty(prop);
 }
 
diff --git a/Source/cmGetPropertyCommand.cxx b/Source/cmGetPropertyCommand.cxx
index ba03568..39445dd 100644
--- a/Source/cmGetPropertyCommand.cxx
+++ b/Source/cmGetPropertyCommand.cxx
@@ -6,6 +6,7 @@
 #include "cmPropertyDefinition.h"
 #include "cmSourceFile.h"
 #include "cmState.h"
+#include "cmTargetPropertyComputer.h"
 #include "cmTest.h"
 #include "cmake.h"
 
@@ -246,8 +247,18 @@ bool cmGetPropertyCommand::HandleTargetMode()
       }
       return this->StoreResult(CM_NULLPTR);
     }
-    return this->StoreResult(
-      target->GetProperty(this->PropertyName, this->Makefile));
+    const char* prop_cstr = 0;
+    cmListFileBacktrace bt = this->Makefile->GetBacktrace();
+    cmMessenger* messenger = this->Makefile->GetMessenger();
+    if (cmTargetPropertyComputer::PassesWhitelist(
+          target->GetType(), this->PropertyName, messenger, bt)) {
+      prop_cstr =
+        target->GetComputedProperty(this->PropertyName, messenger, bt);
+      if (!prop_cstr) {
+        prop_cstr = target->GetProperty(this->PropertyName);
+      }
+    }
+    return this->StoreResult(prop_cstr);
   }
   std::ostringstream e;
   e << "could not find TARGET " << this->Name
diff --git a/Source/cmGetTargetPropertyCommand.cxx b/Source/cmGetTargetPropertyCommand.cxx
index fe09442..6a816d8 100644
--- a/Source/cmGetTargetPropertyCommand.cxx
+++ b/Source/cmGetTargetPropertyCommand.cxx
@@ -2,6 +2,8 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmGetTargetPropertyCommand.h"
 
+#include "cmTargetPropertyComputer.h"
+
 // cmSetTargetPropertyCommand
 bool cmGetTargetPropertyCommand::InitialPass(
   std::vector<std::string> const& args, cmExecutionStatus&)
@@ -22,7 +24,16 @@ bool cmGetTargetPropertyCommand::InitialPass(
         prop_exists = true;
       }
     } else if (!args[2].empty()) {
-      const char* prop_cstr = tgt->GetProperty(args[2], this->Makefile);
+      const char* prop_cstr = 0;
+      cmListFileBacktrace bt = this->Makefile->GetBacktrace();
+      cmMessenger* messenger = this->Makefile->GetMessenger();
+      if (cmTargetPropertyComputer::PassesWhitelist(tgt->GetType(), args[2],
+                                                    messenger, bt)) {
+        prop_cstr = tgt->GetComputedProperty(args[2], messenger, bt);
+        if (!prop_cstr) {
+          prop_cstr = tgt->GetProperty(args[2]);
+        }
+      }
       if (prop_cstr) {
         prop = prop_cstr;
         prop_exists = true;
diff --git a/Source/cmTarget.cxx b/Source/cmTarget.cxx
index 9b2043c..e80768d 100644
--- a/Source/cmTarget.cxx
+++ b/Source/cmTarget.cxx
@@ -1129,28 +1129,15 @@ void cmTarget::CheckProperty(const std::string& prop,
   }
 }
 
-const char* cmTarget::GetProperty(const std::string& prop) const
+const char* cmTarget::GetComputedProperty(
+  const std::string& prop, cmMessenger* messenger,
+  cmListFileBacktrace const& context) const
 {
-  return this->GetProperty(prop, this->Makefile);
+  return cmTargetPropertyComputer::GetProperty(this, prop, messenger, context);
 }
 
-const char* cmTarget::GetProperty(const std::string& prop,
-                                  cmMakefile* context) const
+const char* cmTarget::GetProperty(const std::string& prop) const
 {
-  if (!cmTargetPropertyComputer::PassesWhitelist(this->GetType(), prop,
-                                                 context->GetMessenger(),
-                                                 context->GetBacktrace())) {
-    return CM_NULLPTR;
-  }
-
-  if (const char* result = cmTargetPropertyComputer::GetProperty(
-        this, prop, context->GetMessenger(), context->GetBacktrace())) {
-    return result;
-  }
-  if (cmSystemTools::GetFatalErrorOccured()) {
-    return CM_NULLPTR;
-  }
-
   static UNORDERED_SET<std::string> specialProps;
 #define MAKE_STATIC_PROP(PROP) static const std::string prop##PROP = #PROP
   MAKE_STATIC_PROP(LINK_LIBRARIES);
diff --git a/Source/cmTarget.h b/Source/cmTarget.h
index 2d259ed..bd00b3d 100644
--- a/Source/cmTarget.h
+++ b/Source/cmTarget.h
@@ -200,9 +200,11 @@ public:
   void AppendProperty(const std::string& prop, const char* value,
                       bool asString = false);
   const char* GetProperty(const std::string& prop) const;
-  const char* GetProperty(const std::string& prop, cmMakefile* context) const;
   bool GetPropertyAsBool(const std::string& prop) const;
   void CheckProperty(const std::string& prop, cmMakefile* context) const;
+  const char* GetComputedProperty(const std::string& prop,
+                                  cmMessenger* messenger,
+                                  cmListFileBacktrace const& context) const;
 
   bool IsImported() const { return this->IsImportedTarget; }
   bool IsImportedGloballyVisible() const