CPack allow RPM and DEB generator to be used on OSX.

More generally add the check for possible generator "activation" at
runtime depending on a generator specific check.
The dynamic behavior is currently implemented only for MacOS
and should be fully backward compatible for other system.

Inspired-By Tom Hughes <tomtheengineer@gmail.com>

Source/CPack/cmCPackDebGenerator.h

@@ -31,6 +31,17 @@ public:
   cmCPackDebGenerator();
   virtual ~cmCPackDebGenerator();
 
+  static bool CanGenerate()
+    {
+#ifdef __APPLE__
+    // on MacOS enable CPackDeb iff dpkg is found
+    return cmSystemTools::FindProgram("dpkg") != "" ? true : false;
+#else
+    // legacy behavior on other systems
+    return true;
+#endif
+    }
+
 protected:
   virtual int InitializeInternal();
   /**

Source/CPack/cmCPackGenerator.h

@@ -62,6 +62,16 @@ public:
     { this->GeneratorVerbose = val ?
       cmSystemTools::OUTPUT_MERGE : cmSystemTools::OUTPUT_NONE; }
 
+  /**
+   * Returns true if the generator may work on this system.
+   * Rational:
+   * Some CPack generator may run on some host and may not on others
+   * (with the same system) because some tools are missing. If the tool
+   * is missing then CPack won't activate (in the CPackGeneratorFactory)
+   * this particular generator.
+   */
+  static bool CanGenerate() { return true; }
+
   /**
    * Do the actual whole package processing.
    * Subclass may redefine it but its usually enough

Source/CPack/cmCPackGeneratorFactory.cxx

@@ -31,7 +31,7 @@
 #  include "cmCPackCygwinSourceGenerator.h"
 #endif
 
-#if !defined(_WIN32) && !defined(__APPLE__) \
+#if !defined(_WIN32) \
  && !defined(__QNXNTO__) && !defined(__BEOS__)
 #  include "cmCPackDebGenerator.h"
 #  include "cmCPackRPMGenerator.h"
@@ -42,42 +42,84 @@
 
 //----------------------------------------------------------------------
 cmCPackGeneratorFactory::cmCPackGeneratorFactory()
+{
+  if (cmCPackTGZGenerator::CanGenerate())
     {
     this->RegisterGenerator("TGZ", "Tar GZip compression",
       cmCPackTGZGenerator::CreateGenerator);
+    }
+  if (cmCPackSTGZGenerator::CanGenerate())
+    {
     this->RegisterGenerator("STGZ", "Self extracting Tar GZip compression",
       cmCPackSTGZGenerator::CreateGenerator);
+    }
+  if (cmCPackNSISGenerator::CanGenerate())
+    {
     this->RegisterGenerator("NSIS", "Null Soft Installer",
       cmCPackNSISGenerator::CreateGenerator);
+    }
 #ifdef __CYGWIN__
+  if (cmCPackCygwinBinaryGenerator::CanGenerate())
+    {
     this->RegisterGenerator("CygwinBinary", "Cygwin Binary Installer",
                             cmCPackCygwinBinaryGenerator::CreateGenerator);
+    }
+  if (cmCPackCygwinSourceGenerator::CanGenerate())
+    {
     this->RegisterGenerator("CygwinSource", "Cygwin Source Installer",
                             cmCPackCygwinSourceGenerator::CreateGenerator);
+    }
 #endif
 
+  if (cmCPackZIPGenerator::CanGenerate())
+    {
     this->RegisterGenerator("ZIP", "ZIP file format",
       cmCPackZIPGenerator::CreateGenerator);
+    }
+  if (cmCPackTarBZip2Generator::CanGenerate())
+    {
     this->RegisterGenerator("TBZ2", "Tar BZip2 compression",
       cmCPackTarBZip2Generator::CreateGenerator);
+    }
+  if (cmCPackTarCompressGenerator::CanGenerate())
+    {
     this->RegisterGenerator("TZ", "Tar Compress compression",
       cmCPackTarCompressGenerator::CreateGenerator);
+    }
 #ifdef __APPLE__
+  if (cmCPackDragNDropGenerator::CanGenerate())
+    {
     this->RegisterGenerator("DragNDrop", "Mac OSX Drag And Drop",
       cmCPackDragNDropGenerator::CreateGenerator);
+    }
+  if (cmCPackBundleGenerator::CanGenerate())
+    {
     this->RegisterGenerator("Bundle", "Mac OSX bundle",
       cmCPackBundleGenerator::CreateGenerator);
+    }
+  if (cmCPackPackageMakerGenerator::CanGenerate())
+    {
     this->RegisterGenerator("PackageMaker", "Mac OSX Package Maker installer",
       cmCPackPackageMakerGenerator::CreateGenerator);
+    }
+  if (cmCPackOSXX11Generator::CanGenerate())
+    {
     this->RegisterGenerator("OSXX11", "Mac OSX X11 bundle",
       cmCPackOSXX11Generator::CreateGenerator);
+    }
 #endif
-#if !defined(_WIN32) && !defined(__APPLE__) \
+#if !defined(_WIN32) \
   && !defined(__QNXNTO__) && !defined(__BEOS__)
+  if (cmCPackDebGenerator::CanGenerate())
+    {
     this->RegisterGenerator("DEB", "Debian packages",
       cmCPackDebGenerator::CreateGenerator);
+    }
+  if (cmCPackRPMGenerator::CanGenerate())
+    {
     this->RegisterGenerator("RPM", "RPM packages",
       cmCPackRPMGenerator::CreateGenerator);
+    }
 #endif
 }
 

Source/CPack/cmCPackRPMGenerator.h

@@ -35,6 +35,17 @@ public:
   cmCPackRPMGenerator();
   virtual ~cmCPackRPMGenerator();
 
+  static bool CanGenerate()
+    {
+#ifdef __APPLE__
+    // on MacOS enable CPackRPM iff rpmbuild is found
+    return cmSystemTools::FindProgram("rpmbuild") != "" ? true : false;
+#else
+    // legacy behavior on other systems
+    return true;
+#endif
+    }
+
 protected:
   virtual int InitializeInternal();
   virtual int PackageFiles();

Tests/CMakeLists.txt

@@ -699,6 +699,31 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
   ENDIF(CTEST_RUN_CPackComponents)
 
   IF(CTEST_RUN_CPackComponentsForAll)
+    # Analyze 'cpack --help' output for list of available generators:
+    execute_process(COMMAND ${CMAKE_CPACK_COMMAND} --help
+      RESULT_VARIABLE result
+      OUTPUT_VARIABLE stdout
+      ERROR_VARIABLE stderr)
+
+    string(REPLACE ";" "\\;" stdout "${stdout}")
+    string(REPLACE "\n" "E;" stdout "${stdout}")
+
+    set(collecting 0)
+    set(ACTIVE_CPACK_GENERATORS)
+    foreach(eline ${stdout})
+      string(REGEX REPLACE "^(.*)E$" "\\1" line "${eline}")
+      if(collecting AND NOT line STREQUAL "")
+        string(REGEX REPLACE "^  ([^ ]+) += (.*)$" "\\1" gen "${line}")
+        string(REGEX REPLACE "^  ([^ ]+) += (.*)$" "\\2" doc "${line}")
+        list(APPEND ACTIVE_CPACK_GENERATORS ${gen})
+      endif()
+      if(line STREQUAL "Generators")
+        set(collecting 1)
+      endif()
+    endforeach()
+    # ACTIVE_CPACK_GENERATORS variable
+    # now contains the list of 'active generators'
+
     set(CPackComponentsForAll_EXTRA_OPTIONS)
     set(CPackRun_CPackCommand "-DCPackCommand=${CMAKE_CPACK_COMMAND}")
     # set up list of CPack generators
@@ -706,18 +731,17 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
     if(APPLE)
       list(APPEND GENLST "DragNDrop")
     endif(APPLE)
-    if (CMAKE_SYSTEM_NAME MATCHES "Linux" AND NOT CMAKE_CURRENT_BINARY_DIR MATCHES ".* .*")
+    if (NOT CMAKE_CURRENT_BINARY_DIR MATCHES ".* .*")
-        find_program(RPMBUILD NAMES rpmbuild)
+      list(FIND ACTIVE_CPACK_GENERATORS "RPM" RPM_ACTIVE)
-    endif(CMAKE_SYSTEM_NAME MATCHES "Linux" AND NOT CMAKE_CURRENT_BINARY_DIR MATCHES ".* .*")
+      if (NOT ${RPM_ACTIVE} EQUAL -1)
-    if (RPMBUILD)
         list(APPEND GENLST "RPM")
-    endif(RPMBUILD)
+      endif(NOT ${RPM_ACTIVE} EQUAL -1)
-    if (CMAKE_SYSTEM_NAME MATCHES "Linux")
+    endif(NOT CMAKE_CURRENT_BINARY_DIR MATCHES ".* .*")
-       find_program(DPKG NAMES dpkg)
+    list(FIND ACTIVE_CPACK_GENERATORS "DEB" DEB_ACTIVE)
-       if (DPKG)
+    if (NOT ${DEB_ACTIVE} EQUAL -1)
       list(APPEND GENLST "DEB")
-       endif(DPKG)
+    endif(NOT ${DEB_ACTIVE} EQUAL -1)
-    endif(CMAKE_SYSTEM_NAME MATCHES "Linux")
+
     # set up list of component packaging ways
     list(APPEND CWAYLST "default")
     list(APPEND CWAYLST "OnePackPerGroup")