ENH: Add unset() command.

This introduces the unset() command to make it easy to unset CMake
variables, environment variables, and CMake cache variables.  Previously
it was not even possible to unset ENV or CACHE variables (as in
completely remove them).  Changes based on patch from Philip Lowman.
See issue #7507.

7 files changed, 160 insertions, 6 deletions

diff --git a/Source/cmBootstrapCommands.cxx b/Source/cmBootstrapCommands.cxx
index b8031fc..f14b024 100644
--- a/Source/cmBootstrapCommands.cxx
+++ b/Source/cmBootstrapCommands.cxx
@@ -93,6 +93,7 @@
 #include "cmTargetLinkLibrariesCommand.cxx"
 #include "cmTryCompileCommand.cxx"
 #include "cmTryRunCommand.cxx"
+#include "cmUnsetCommand.cxx"
 
 void GetBootstrapCommands(std::list<cmCommand*>& commands)
 {
@@ -163,4 +164,5 @@ void GetBootstrapCommands(std::list<cmCommand*>& commands)
   commands.push_back(new cmTargetLinkLibrariesCommand);
   commands.push_back(new cmTryCompileCommand);
   commands.push_back(new cmTryRunCommand);
+  commands.push_back(new cmUnsetCommand);
 }
diff --git a/Source/cmCacheManager.cxx b/Source/cmCacheManager.cxx
index bd95354..52cb448 100644
--- a/Source/cmCacheManager.cxx
+++ b/Source/cmCacheManager.cxx
@@ -714,10 +714,6 @@ void cmCacheManager::RemoveCacheEntry(const char* key)
     {
     this->Cache.erase(i);
     }
-  else
-    {
-    std::cerr << "Failed to remove entry:" << key << std::endl;
-    }
 }
 
 
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 102ca44..a251462 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -1648,6 +1648,11 @@ void cmMakefile::RemoveDefinition(const char* name)
 #endif
 }
 
+void cmMakefile::RemoveCacheDefinition(const char* name)
+{
+  this->GetCacheManager()->RemoveCacheEntry(name);
+}
+
 void cmMakefile::SetProjectName(const char* p)
 {
   this->ProjectName = p;
diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index f9d10b6..f78a1dd 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -278,6 +278,8 @@ public:
    * for cache entries, and will only affect the current makefile.
    */
   void RemoveDefinition(const char* name);
+  ///! Remove a definition from the cache.
+  void RemoveCacheDefinition(const char* name);
   
   /**
    * Specify the name of the project for this build.
diff --git a/Source/cmSetCommand.h b/Source/cmSetCommand.h
index e818d6a..39d0bc3 100644
--- a/Source/cmSetCommand.h
+++ b/Source/cmSetCommand.h
@@ -87,8 +87,9 @@ public:
       "above the current scope. Each new directory or function creates a new "
       "scope. This command will set the value of a variable into the parent "
       "directory or calling function (whichever is applicable to the case at "
-      "hand) If VALUE is not specified then the variable is removed from the "
-      "parent scope.\n"
+      "hand).\n"
+      "If <value> is not specified then the variable is removed "
+      "instead of set.  See also: the unset() command.\n"
       "  set(<variable> <value1> ... <valueN>)\n"
       "In this case <variable> is set to a semicolon separated list of "
       "values.\n"
diff --git a/Source/cmUnsetCommand.cxx b/Source/cmUnsetCommand.cxx
new file mode 100644
index 0000000..d45b50b
--- /dev/null
+++ b/Source/cmUnsetCommand.cxx
@@ -0,0 +1,64 @@
+/*=========================================================================
+
+  Program:   CMake - Cross-Platform Makefile Generator
+  Module:    $RCSfile$
+  Language:  C++
+  Date:      $Date$
+  Version:   $Revision$
+
+  Copyright (c) 2002 Kitware, Inc., Insight Consortium.  All rights reserved.
+  See Copyright.txt or http://www.cmake.org/HTML/Copyright.html for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notices for more information.
+
+=========================================================================*/
+#include "cmUnsetCommand.h"
+
+// cmUnsetCommand
+bool cmUnsetCommand::InitialPass(std::vector<std::string> const& args,
+                                 cmExecutionStatus &)
+{
+  if(args.size() < 1 || args.size() > 2)
+    {
+    this->SetError("called with incorrect number of arguments");
+    return false;
+    }
+
+  const char* variable = args[0].c_str();
+
+  // unset(ENV{VAR})
+  if (!strncmp(variable,"ENV{",4) && strlen(variable) > 5)
+    {
+    // what is the variable name
+    char *envVarName = new char [strlen(variable)];
+    strncpy(envVarName,variable+4,strlen(variable)-5);
+    envVarName[strlen(variable)-5] = '\0';
+
+#ifdef CMAKE_BUILD_WITH_CMAKE
+    cmSystemTools::UnsetEnv(envVarName);
+#endif
+    delete[] envVarName;
+    return true;
+    }
+  // unset(VAR)
+  else if (args.size() == 1)
+    {
+    this->Makefile->RemoveDefinition(variable);
+    return true;
+    }
+  // unset(VAR CACHE)
+  else if ((args.size() == 2) && (args[1] == "CACHE"))
+    {
+    this->Makefile->RemoveCacheDefinition(variable);
+    return true;
+    }
+  // ERROR: second argument isn't CACHE
+  else
+    {
+    this->SetError("called with an invalid second argument");
+    return false;
+    }
+}
+
diff --git a/Source/cmUnsetCommand.h b/Source/cmUnsetCommand.h
new file mode 100644
index 0000000..d125a18
--- /dev/null
+++ b/Source/cmUnsetCommand.h
@@ -0,0 +1,84 @@
+/*=========================================================================
+
+  Program:   CMake - Cross-Platform Makefile Generator
+  Module:    $RCSfile$
+  Language:  C++
+  Date:      $Date$
+  Version:   $Revision$
+
+  Copyright (c) 2002 Kitware, Inc., Insight Consortium.  All rights reserved.
+  See Copyright.txt or http://www.cmake.org/HTML/Copyright.html for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notices for more information.
+
+=========================================================================*/
+#ifndef cmUnsetCommand_h
+#define cmUnsetCommand_h
+
+#include "cmCommand.h"
+
+/** \class cmUnsetCommand
+ * \brief Unset a CMAKE variable
+ *
+ * cmUnsetCommand unsets or removes a variable.
+ */
+class cmUnsetCommand : public cmCommand
+{
+public:
+  /**
+   * This is a virtual constructor for the command.
+   */
+  virtual cmCommand* Clone()
+    {
+    return new cmUnsetCommand;
+    }
+
+  /**
+   * This is called when the command is first encountered in
+   * the CMakeLists.txt file.
+   */
+  virtual bool InitialPass(std::vector<std::string> const& args,
+                           cmExecutionStatus &status);
+
+  /**
+   * This determines if the command is invoked when in script mode.
+   */
+  virtual bool IsScriptable() { return true; }
+
+  /**
+   * The name of the command as specified in CMakeList.txt.
+   */
+  virtual const char* GetName() {return "unset";}
+
+  /**
+   * Succinct documentation.
+   */
+  virtual const char* GetTerseDocumentation()
+    {
+    return "Unset a variable, cache variable, or environment variable.";
+    }
+
+  /**
+   * More documentation.
+   */
+  virtual const char* GetFullDocumentation()
+    {
+    return
+      "  unset(<variable> [CACHE])\n"
+      "Removes the specified variable causing it to become undefined.  "
+      "If CACHE is present then the variable is removed from the cache "
+      "instead of the current scope.\n"
+      "<variable> can be an environment variable such as:\n"
+      "  unset(ENV{LD_LIBRARY_PATH})\n"
+      "in which case the variable will be removed from the current "
+      "environment.";
+    }
+
+  cmTypeMacro(cmUnsetCommand, cmCommand);
+};
+
+
+
+#endif