install(EXPORT): Enforce existence of imported target files

Typical <package>Config.cmake files for find_package() rely only on the
files generated by install(EXPORT).  They might be wrong, for whatever
reasons, like people manually deleted files, projects were packaged
wrong by distributions, whatever.  To protect against this, add checks
that the file locations we are importing actually exist on disk.

Alex

Source/cmExportFileGenerator.cxx

@@ -368,3 +368,69 @@ cmExportFileGenerator
   os << "  )\n"
      << "\n";
 }
+
+
+//----------------------------------------------------------------------------
+void
+cmExportFileGenerator::GenerateImportedFileCheckLoop(std::ostream& os)
+{
+  // Add code which verifies at cmake time that the file which is being
+  // imported actually exists on disk. This should in theory always be theory
+  // case, but still when packages are split into normal and development
+  // packages this might get broken (e.g. the Config.cmake could be part of
+  // the non-development package, something similar happened to me without
+  // on SUSE with a mysql pkg-config file, which claimed everything is fine,
+  // but the development package was not installed.).
+  os << "# Loop over all imported files and verify that they actually exist\n"
+        "FOREACH(target ${_IMPORT_CHECK_TARGETS} )\n"
+        "  FOREACH(file ${_IMPORT_CHECK_FILES_FOR_${target}} )\n"
+        "    IF(NOT EXISTS \"${file}\" )\n"
+        "      MESSAGE(FATAL_ERROR \"The imported target \\\"${target}\\\" "
+        "references the file \\\"${file}\\\", but this file does not exist. "
+        "There are multiple possible reasons:\n"
+        " * The file \\\"${file}\\\" has been manually "
+        "deleted, renamed or moved to another location.\n"
+        " * A previous install or uninstall procedure did not complete "
+        " successfully.\n"
+        " * The installation package was faulty, and contained\n"
+        "\\\"${CMAKE_CURRENT_LIST_FILE}\\\"\n"
+        "but not\n"
+        "\\\"${file}\\\"\n"
+        "which must always be installed together.\\n\"\n"
+        "             )\n"
+        "    ENDIF()\n"
+        "  ENDFOREACH()\n"
+        "  UNSET(_IMPORT_CHECK_FILES_FOR_${target})\n"
+        "ENDFOREACH()\n"
+        "UNSET(_IMPORT_CHECK_TARGETS)\n"
+        "\n";
+}
+
+
+//----------------------------------------------------------------------------
+void
+cmExportFileGenerator
+::GenerateImportedFileChecksCode(std::ostream& os, cmTarget* target,
+                                 ImportPropertyMap const& properties,
+                                const std::set<std::string>& importedLocations)
+{
+  // Construct the imported target name.
+  std::string targetName = this->Namespace;
+  targetName += target->GetName();
+
+  os << "LIST(APPEND _IMPORT_CHECK_TARGETS " << targetName << " )\n"
+        "LIST(APPEND _IMPORT_CHECK_FILES_FOR_" << targetName << " ";
+
+  for(std::set<std::string>::const_iterator li = importedLocations.begin();
+      li != importedLocations.end();
+      ++li)
+    {
+    ImportPropertyMap::const_iterator pi = properties.find(*li);
+    if (pi != properties.end())
+      {
+      os << "\"" << pi->second << "\" ";
+      }
+    }
+
+  os << ")\n\n";
+}

Source/cmExportFileGenerator.h

@@ -56,6 +56,11 @@ protected:
   void GenerateImportPropertyCode(std::ostream& os, const char* config,
                                   cmTarget* target,
                                   ImportPropertyMap const& properties);
+  void GenerateImportedFileChecksCode(std::ostream& os, cmTarget* target,
+                                      ImportPropertyMap const& properties,
+                               const std::set<std::string>& importedLocations);
+  void GenerateImportedFileCheckLoop(std::ostream& os);
+
 
   // Collect properties with detailed information about targets beyond
   // their location on disk.

Source/cmExportInstallFileGenerator.cxx

@@ -167,16 +167,18 @@ cmExportInstallFileGenerator
     // Collect import properties for this target.
     cmTargetExport* te = *tei;
     ImportPropertyMap properties;
+    std::set<std::string> importedLocations;
+    this->SetImportLocationProperty(config, suffix, te->ArchiveGenerator,
+                                    properties, importedLocations);
+    this->SetImportLocationProperty(config, suffix, te->LibraryGenerator,
+                                    properties, importedLocations);
     this->SetImportLocationProperty(config, suffix,
-                                    te->ArchiveGenerator, properties);
+                                    te->RuntimeGenerator, properties,
-    this->SetImportLocationProperty(config, suffix,
+                                    importedLocations);
-                                    te->LibraryGenerator, properties);
+    this->SetImportLocationProperty(config, suffix, te->FrameworkGenerator,
-    this->SetImportLocationProperty(config, suffix,
+                                    properties, importedLocations);
-                                    te->RuntimeGenerator, properties);
+    this->SetImportLocationProperty(config, suffix, te->BundleGenerator,
-    this->SetImportLocationProperty(config, suffix,
+                                    properties, importedLocations);
-                                    te->FrameworkGenerator, properties);
-    this->SetImportLocationProperty(config, suffix,
-                                    te->BundleGenerator, properties);
 
     // If any file location was set for the target add it to the
     // import file.
@@ -194,9 +196,13 @@ cmExportInstallFileGenerator
 
       // Generate code in the export file.
       this->GenerateImportPropertyCode(os, config, te->Target, properties);
+      this->GenerateImportedFileChecksCode(os, te->Target, properties,
+                                           importedLocations);
       }
     }
 
+  this->GenerateImportedFileCheckLoop(os);
+
   // Cleanup the import prefix variable.
   if(!this->ImportPrefix.empty())
     {
@@ -211,7 +217,9 @@ void
 cmExportInstallFileGenerator
 ::SetImportLocationProperty(const char* config, std::string const& suffix,
                             cmInstallTargetGenerator* itgen,
-                            ImportPropertyMap& properties)
+                            ImportPropertyMap& properties,
+                            std::set<std::string>& importedLocations
+                           )
 {
   // Skip rules that do not match this configuration.
   if(!(itgen && itgen->InstallsForConfig(config)))
@@ -249,6 +257,7 @@ cmExportInstallFileGenerator
 
     // Store the property.
     properties[prop] = value;
+    importedLocations.insert(prop);
     }
   else
     {
@@ -291,6 +300,7 @@ cmExportInstallFileGenerator
 
     // Store the property.
     properties[prop] = value;
+    importedLocations.insert(prop);
     }
 }
 

Source/cmExportInstallFileGenerator.h

@@ -75,7 +75,9 @@ protected:
   void SetImportLocationProperty(const char* config,
                                  std::string const& suffix,
                                  cmInstallTargetGenerator* itgen,
-                                 ImportPropertyMap& properties);
+                                 ImportPropertyMap& properties,
+                                 std::set<std::string>& importedLocations
+                                );
 
   void ComplainAboutImportPrefix(cmInstallTargetGenerator* itgen);