exports: accept a missing target if it is exported exactly once

If a target is exported, and a library it depends on is not part
of the same export set, before this patch cmake errored out.
With this patch, it now checks whether the missing target
is exported somewhere else exactly once, and accepts in this
case (because then it can determine the namespace for the
missing target and use this).

Alex

Source/cmExportBuildFileGenerator.cxx

@@ -135,7 +135,8 @@ cmExportBuildFileGenerator
 void
 cmExportBuildFileGenerator
 ::ComplainAboutMissingTarget(cmTarget* depender,
-                             cmTarget* dependee)
+                             cmTarget* dependee,
+                             int occurrences)
 {
   if(!this->ExportCommand || !this->ExportCommand->ErrorMessage.empty())
     {
@@ -143,10 +144,20 @@ cmExportBuildFileGenerator
     }
 
   cmOStringStream e;
-  e << "called with target \"" << depender->GetName()
-    << "\" which requires target \"" << dependee->GetName()
-    << "\" that is not in the export list.\n"
-    << "If the required target is not easy to reference in this call, "
-    << "consider using the APPEND option with multiple separate calls.";
+  if (occurrences == 0)
+    {
+    e << "called with target \"" << depender->GetName()
+      << "\" which requires target \"" << dependee->GetName()
+      << "\" that is not in the export list.\n"
+      << "If the required target is not easy to reference in this call, "
+      << "consider using the APPEND option with multiple separate calls.";
+    }
+  else
+    {
+    e << "called with target \"" << depender->GetName()
+      << "\" which requires target \"" << dependee->GetName()
+      << "\" that is exported " << occurrences << " times in other "
+      << "export ""lists.\n";
+    }
   this->ExportCommand->ErrorMessage = e.str();
 }

Source/cmExportBuildFileGenerator.h

@@ -46,7 +46,8 @@ protected:
                                            const char* config,
                                            std::string const& suffix);
   virtual void ComplainAboutMissingTarget(cmTarget* depender,
-                                          cmTarget* dependee);
+                                          cmTarget* dependee,
+                                          int occurrences);
 
   /** Fill in properties indicating built file locations.  */
   void SetImportLocationProperty(const char* config,

Source/cmExportFileGenerator.cxx

@@ -11,10 +11,15 @@
 ============================================================================*/
 #include "cmExportFileGenerator.h"
 
+#include "cmExportSet.h"
 #include "cmGeneratedFileStream.h"
+#include "cmGlobalGenerator.h"
+#include "cmInstallExportGenerator.h"
+#include "cmLocalGenerator.h"
 #include "cmMakefile.h"
 #include "cmSystemTools.h"
 #include "cmTarget.h"
+#include "cmTargetExport.h"
 #include "cmVersion.h"
 
 #include <cmsys/auto_ptr.hxx>
@@ -224,17 +229,28 @@ cmExportFileGenerator
         }
       else
         {
-        // The target is not in the export.
-        if(!this->AppendMode)
+        std::vector<std::string> namespaces = this->FindNamespaces(mf, *li);
+        int targetOccurrences = (int)namespaces.size();
+
+        if (targetOccurrences == 1)
           {
-          // We are not appending, so all exported targets should be
-          // known here.  This is probably user-error.
-          this->ComplainAboutMissingTarget(target, tgt);
+          link_libs += namespaces[0];
+          link_libs += *li;
+          }
+        else
+          {
+          // The target is not in the export.
+          if(!this->AppendMode)
+            {
+            // We are not appending, so all exported targets should be
+            // known here.  This is probably user-error.
+            this->ComplainAboutMissingTarget(target, tgt, targetOccurrences);
+            }
+          // Assume the target will be exported by another command.
+          // Append it with the export namespace.
+          link_libs += this->Namespace;
+          link_libs += *li;
           }
-        // Assume the target will be exported by another command.
-        // Append it with the export namespace.
-        link_libs += this->Namespace;
-        link_libs += *li;
         }
       }
     else
@@ -250,6 +266,48 @@ cmExportFileGenerator
   properties[prop] = link_libs;
 }
 
+
+//----------------------------------------------------------------------------
+std::vector<std::string> cmExportFileGenerator::FindNamespaces(cmMakefile* mf,
+                                                       const std::string& name)
+{
+  std::vector<std::string> namespaces;
+  cmGlobalGenerator* gg = mf->GetLocalGenerator()->GetGlobalGenerator();
+  const cmExportSetMap& exportSets = gg->GetExportSets();
+
+  for(cmExportSetMap::const_iterator expIt = exportSets.begin();
+      expIt != exportSets.end();
+      ++expIt)
+    {
+    const cmExportSet* exportSet = expIt->second;
+    std::vector<cmTargetExport const*> const* targets =
+                                                 exportSet->GetTargetExports();
+
+    bool containsTarget = false;
+    for(unsigned int i=0; i<targets->size(); i++)
+      {
+      if (name == (*targets)[i]->Target->GetName())
+        {
+        containsTarget = true;
+        break;
+        }
+      }
+
+    if (containsTarget)
+      {
+      std::vector<cmInstallExportGenerator const*> const* installs =
+                                                 exportSet->GetInstallations();
+      for(unsigned int i=0; i<installs->size(); i++)
+        {
+        namespaces.push_back((*installs)[i]->GetNamespace());
+        }
+      }
+    }
+
+  return namespaces;
+}
+
+
 //----------------------------------------------------------------------------
 void cmExportFileGenerator::GenerateImportHeaderCode(std::ostream& os,
                                                      const char* config)

Source/cmExportFileGenerator.h

@@ -83,7 +83,12 @@ protected:
   /** Each subclass knows how to complain about a target that is
       missing from an export set.  */
   virtual void ComplainAboutMissingTarget(cmTarget* depender,
-                                          cmTarget* dependee) = 0;
+                                          cmTarget* dependee,
+                                          int occurrences) = 0;
+
+  std::vector<std::string> FindNamespaces(cmMakefile* mf,
+                                          const std::string& name);
+
 
   // The namespace in which the exports are placed in the generated file.
   std::string Namespace;

Source/cmExportInstallFileGenerator.cxx

@@ -327,14 +327,24 @@ cmExportInstallFileGenerator
 //----------------------------------------------------------------------------
 void
 cmExportInstallFileGenerator
-::ComplainAboutMissingTarget(cmTarget* depender, cmTarget* dependee)
+::ComplainAboutMissingTarget(cmTarget* depender,
+                             cmTarget* dependee,
+                             int occurrences)
 {
   cmOStringStream e;
   e << "INSTALL(EXPORT \""
     << this->IEGen->GetExportSet()->GetName()
     << "\" ...) "
     << "includes target \"" << depender->GetName()
-    << "\" which requires target \"" << dependee->GetName()
-    << "\" that is not in the export set.";
+    << "\" which requires target \"" << dependee->GetName() << "\" ";
+  if (occurrences == 0)
+    {
+    e << "that is not in the export set.";
+    }
+  else
+    {
+    e << "that is not in this export set, but " << occurrences
+    << " times in others.";
+    }
   cmSystemTools::Error(e.str().c_str());
 }

Source/cmExportInstallFileGenerator.h

@@ -58,7 +58,8 @@ protected:
                                            const char* config,
                                            std::string const& suffix);
   virtual void ComplainAboutMissingTarget(cmTarget* depender,
-                                          cmTarget* dependee);
+                                          cmTarget* dependee,
+                                          int occurrences);
 
   /** Generate a per-configuration file for the targets.  */
   bool GenerateImportFileConfig(const char* config);

Source/cmInstallExportGenerator.h

@@ -34,7 +34,10 @@ public:
                            cmMakefile* mf);
   ~cmInstallExportGenerator();
 
-  cmExportSet* GetExportSet() {return ExportSet;}
+  cmExportSet* GetExportSet() {return this->ExportSet;}
+
+  const std::string& GetNamespace() const { return this->Namespace; }
+
 protected:
   virtual void GenerateScript(std::ostream& os);
   virtual void GenerateScriptConfigs(std::ostream& os, Indent const& indent);