Add API to extract target names from a genex string.

The TARGET_NAME expression, which requires a literal, provides
target names. $<TARGET_PROPERTY:tgt,prop> also provides target
names in the cases where tgt is a literal, so that TARGET_NAME is
not needed then in addition.

Source/cmExportFileGenerator.cxx

@@ -124,6 +124,142 @@ void cmExportFileGenerator::GenerateImportConfig(std::ostream& os,
   this->GenerateImportTargetsConfig(os, config, suffix);
 }
 
+//----------------------------------------------------------------------------
+void
+cmExportFileGenerator::ResolveTargetsInGeneratorExpressions(
+                                    std::string &input,
+                                    cmTarget* target,
+                                    std::vector<std::string> &missingTargets)
+{
+  std::string::size_type pos = 0;
+  std::string::size_type lastPos = pos;
+
+  cmMakefile *mf = target->GetMakefile();
+  std::string errorString;
+
+  while((pos = input.find("$<TARGET_PROPERTY:", lastPos)) != input.npos)
+    {
+    std::string::size_type nameStartPos = pos +
+                                            sizeof("$<TARGET_PROPERTY:") - 1;
+    std::string::size_type closePos = input.find(">", nameStartPos);
+    std::string::size_type commaPos = input.find(",", nameStartPos);
+    std::string::size_type nextOpenPos = input.find("$<", nameStartPos);
+    if (commaPos == input.npos // Implied 'this' target
+        || closePos == input.npos // Imcomplete expression.
+        || closePos < commaPos // Implied 'this' target
+        || nextOpenPos < commaPos) // Non-literal
+      {
+      lastPos = nameStartPos;
+      continue;
+      }
+
+    const std::string targetName = input.substr(nameStartPos,
+                                                commaPos - nameStartPos);
+
+    pos = nameStartPos; // We're not going to replace the entire expression,
+                        // but only the target parameter.
+    if (cmTarget *tgt = mf->FindTargetToUse(targetName.c_str()))
+      {
+      if(tgt->IsImported())
+        {
+        pos += targetName.size();
+        }
+      else if(this->ExportedTargets.find(tgt) != this->ExportedTargets.end())
+        {
+        input.replace(pos, targetName.size(),
+                      this->Namespace + targetName);
+        pos += this->Namespace.size() + targetName.size();
+        }
+      else
+        {
+        std::string namespacedTarget;
+        this->HandleMissingTarget(namespacedTarget, missingTargets,
+                                  mf, target, tgt);
+        if (!namespacedTarget.empty())
+          {
+          input.replace(pos, targetName.size(), namespacedTarget);
+          pos += namespacedTarget.size();
+          }
+        }
+      }
+    else
+      {
+      errorString = "$<TARGET_PROPERTY:" + targetName + ",prop> requires "
+                    "its first parameter to be a reachable target.";
+      }
+    lastPos = pos;
+    if (!errorString.empty())
+      {
+      break;
+      }
+    }
+  if (!errorString.empty())
+    {
+    mf->IssueMessage(cmake::FATAL_ERROR, errorString);
+    return;
+    }
+
+  pos = 0;
+  lastPos = pos;
+  while((pos = input.find("$<TARGET_NAME:", lastPos)) != input.npos)
+    {
+    std::string::size_type nameStartPos = pos + sizeof("$<TARGET_NAME:") - 1;
+    std::string::size_type endPos = input.find(">", nameStartPos);
+    if (endPos == input.npos)
+      {
+      errorString = "$<TARGET_NAME:...> expression incomplete";
+      }
+    const std::string targetName = input.substr(nameStartPos,
+                                                endPos - nameStartPos);
+    if(targetName.find("$<", lastPos) != input.npos)
+      {
+      errorString = "$<TARGET_NAME:...> requires its parameter to be a "
+                    "literal.";
+      }
+    if (cmTarget *tgt = mf->FindTargetToUse(targetName.c_str()))
+      {
+      if(tgt->IsImported())
+        {
+        input.replace(pos, sizeof("$<TARGET_NAME:") + targetName.size(),
+                      targetName);
+        pos += sizeof("$<TARGET_NAME:") + targetName.size();
+        }
+      else if(this->ExportedTargets.find(tgt) != this->ExportedTargets.end())
+        {
+        input.replace(pos, sizeof("$<TARGET_NAME:") + targetName.size(),
+                      this->Namespace + targetName);
+        pos += sizeof("$<TARGET_NAME:") + targetName.size();
+        }
+      else
+        {
+        std::string namespacedTarget;
+        this->HandleMissingTarget(namespacedTarget, missingTargets,
+                                  mf, target, tgt);
+        if (!namespacedTarget.empty())
+          {
+          input.replace(pos, sizeof("$<TARGET_NAME:") + targetName.size(),
+                        namespacedTarget);
+          pos += sizeof("$<TARGET_NAME:") + targetName.size();
+          }
+        }
+      }
+    else
+      {
+      errorString = "$<TARGET_NAME:...> requires its parameter to be a "
+                    "reachable target.";
+      }
+    lastPos = pos;
+    if (!errorString.empty())
+      {
+      break;
+      }
+    }
+  if (!errorString.empty())
+    {
+    mf->IssueMessage(cmake::FATAL_ERROR, errorString);
+    }
+}
+
 //----------------------------------------------------------------------------
 void
 cmExportFileGenerator

Source/cmExportFileGenerator.h

@@ -94,6 +94,10 @@ protected:
                                    cmTarget* depender,
                                    cmTarget* dependee) = 0;
 
+  void ResolveTargetsInGeneratorExpressions(std::string &input,
+                                    cmTarget* target,
+                                    std::vector<std::string> &missingTargets);
+
   // The namespace in which the exports are placed in the generated file.
   std::string Namespace;