Add a generator expression for target properties.

There are two overloads, so that it can use the operational
target when a target property is being evaluated, and a target
can alternatively be specified by name.

At this point, the generators don't chain. That comes later.

Source/cmAddTestCommand.h

@@ -81,7 +81,7 @@ public:
       "\n"
       "Arguments after COMMAND may use \"generator expressions\" with the "
       "syntax \"$<...>\".  "
-      CM_DOCUMENT_COMMAND_GENERATOR_EXPRESSIONS
+      CM_DOCUMENT_ADD_TEST_GENERATOR_EXPRESSIONS
       "Example usage:\n"
       "  add_test(NAME mytest\n"
       "           COMMAND testDriver --config $<CONFIGURATION>\n"

Source/cmDocumentGeneratorExpressions.h

@@ -12,7 +12,7 @@
 #ifndef cmDocumentGeneratorExpressions_h
 #define cmDocumentGeneratorExpressions_h
 
-#define CM_DOCUMENT_COMMAND_GENERATOR_EXPRESSIONS                       \
+#define CM_DOCUMENT_ADD_TEST_GENERATOR_EXPRESSIONS                      \
   "Generator expressions are evaluted during build system generation "  \
   "to produce information specific to each build configuration.  "      \
   "Valid expressions are:\n"                                            \
@@ -35,11 +35,20 @@
   "  $<TARGET_FILE_DIR:tgt>/$<TARGET_FILE_NAME:tgt>\n"                  \
   "  $<TARGET_LINKER_FILE_DIR:tgt>/$<TARGET_LINKER_FILE_NAME:tgt>\n"    \
   "  $<TARGET_SONAME_FILE_DIR:tgt>/$<TARGET_SONAME_FILE_NAME:tgt>\n"    \
+  "  $<TARGET_PROPERTY:tgt,prop>   = The value of the property prop\n"  \
+  "the target tgt. Note that tgt is not added as a dependency of the "  \
+  "target this expression is evaluated on.\n" \
   "Boolean expressions:\n"                                              \
   "  $<AND:?[,?]...>           = '1' if all '?' are '1', else '0'\n"    \
   "  $<OR:?[,?]...>            = '0' if all '?' are '0', else '1'\n"    \
   "  $<NOT:?>                  = '0' if '?' is '1', else '1'\n"         \
   "where '?' is always either '0' or '1'.\n"                            \
+
+#define CM_DOCUMENT_COMMAND_GENERATOR_EXPRESSIONS                       \
+  CM_DOCUMENT_ADD_TEST_GENERATOR_EXPRESSIONS \
+  "Expressions with an implicit 'this' target:"                         \
+  "  $<TARGET_PROPERTY:prop>   = The value of the property prop on\n"   \
+  "the target on which the generator expression is evaluated.\n"        \
   ""
 
 #endif

Source/cmGeneratorExpression.cxx

@@ -65,7 +65,8 @@ cmGeneratorExpression::~cmGeneratorExpression()
 
 //----------------------------------------------------------------------------
 const char *cmCompiledGeneratorExpression::Evaluate(
-  cmMakefile* mf, const char* config, bool quiet) const
+  cmMakefile* mf, const char* config, bool quiet,
+  cmGeneratorTarget *target) const
 {
   if (!this->NeedsParsing)
     {
@@ -84,6 +85,7 @@ const char *cmCompiledGeneratorExpression::Evaluate(
   context.Config = config;
   context.Quiet = quiet;
   context.HadError = false;
+  context.Target = target;
   context.Backtrace = this->Backtrace;
 
   for ( ; it != end; ++it)

Source/cmGeneratorExpression.h

@@ -20,6 +20,7 @@
 #include <cmsys/RegularExpression.hxx>
 
 class cmTarget;
+class cmGeneratorTarget;
 class cmMakefile;
 class cmListFileBacktrace;
 
@@ -58,7 +59,8 @@ class cmCompiledGeneratorExpression
 {
 public:
   const char* Evaluate(cmMakefile* mf, const char* config,
-                        bool quiet = false) const;
+                       bool quiet = false,
+                       cmGeneratorTarget *target = 0) const;
 
   /** Get set of targets found during evaluations.  */
   std::set<cmTarget*> const& GetTargets() const

Source/cmGeneratorExpressionEvaluator.cxx

@@ -239,6 +239,46 @@ static const struct ConfigurationTestNode : public cmGeneratorExpressionNode
   }
 } configurationTestNode;
 
+//----------------------------------------------------------------------------
+static const struct TargetPropertyNode: public cmGeneratorExpressionNode
+{
+  TargetPropertyNode() {}
+
+  // This node handles errors on parameter count itself.
+  virtual int NumExpectedParameters() const { return -1; }
+
+  std::string Evaluate(const std::vector<std::string> &parameters,
+                       cmGeneratorExpressionContext *context,
+                       const GeneratorExpressionContent *content) const
+  {
+    if (parameters.size() != 1 && parameters.size() != 2)
+      {
+      reportError(context, content->GetOriginalExpression(),
+          "$<TARGET_PROPERTY:...> expression requires one or two parameters");
+      return std::string();
+      }
+    cmGeneratorTarget* target = context->Target;
+    std::string propertyName = *parameters.begin();
+    if (parameters.size() == 2)
+      {
+      target = context->Makefile->FindGeneratorTargetToUse(
+                                                parameters.begin()->c_str());
+
+      if (!target)
+        {
+        cmOStringStream e;
+        e << "Target \""
+          << target
+          << "\" not found.";
+        reportError(context, content->GetOriginalExpression(), e.str());
+        }
+      propertyName = parameters.at(1);
+      }
+    const char *prop = target->GetProperty(propertyName.c_str());
+    return prop ? prop : "";
+  }
+} targetPropertyNode;
+
 //----------------------------------------------------------------------------
 template<bool linker, bool soname>
 struct TargetFilesystemArtifactResultCreator
@@ -460,7 +500,10 @@ cmGeneratorExpressionNode* GetNode(const std::string &identifier)
     return &angle_rNode;
   else if (identifier == "COMMA")
     return &commaNode;
+  else if (identifier == "TARGET_PROPERTY")
+    return &targetPropertyNode;
   return 0;
+
 }
 
 //----------------------------------------------------------------------------

Source/cmGeneratorExpressionEvaluator.h

@@ -15,6 +15,11 @@
 #include <vector>
 #include <string>
 
+#include "cmListFileCache.h"
+
+class cmTarget;
+class cmGeneratorTarget;
+
 //----------------------------------------------------------------------------
 struct cmGeneratorExpressionContext
 {
@@ -22,7 +27,7 @@ struct cmGeneratorExpressionContext
   std::set<cmTarget*> Targets;
   cmMakefile *Makefile;
   const char *Config;
-  cmTarget *Target;
+  cmGeneratorTarget *Target;
   bool Quiet;
   bool HadError;
 };