Do not unset cache variables in KDEInstallDirs.

Cache variables such as CMAKE_INSTALL_BINDIR may be used by other
modules included from parallel parts of the tree, so we should not touch
them. We still override them in the runtime environment, but this will
not interfere with parallel subtrees of the project.

As part of this, the order of precedence of variables specified on the
command line is changed, so that KDE_INSTALL_* is considered first
(although it is still considered "undefined" in the documentation). This
means that if you only specify CMAKE_INSTALL_BINDIR, that will be used
by both KDEInstallDirs and GNUInstallDirs, but if you specify both that
and KDE_INSTALL_BINDIR, KDEInstallDirs will use KDE_INSTALL_BINDIR
instead.  This is probably not too useful, but seems more useful than
any other arrangement.

BUG: 342717
REVIEW: 121982

1 files changed, 20 insertions, 18 deletions

diff --git a/kde-modules/KDEInstallDirs.cmake b/kde-modules/KDEInstallDirs.cmake
index 7d592afc..72a67641 100644
--- a/kde-modules/KDEInstallDirs.cmake
+++ b/kde-modules/KDEInstallDirs.cmake
@@ -163,7 +163,7 @@
 # ``${PROJECT_NAME}`` to provide a sensible default for this CMake option.
 
 #=============================================================================
-# Copyright 2014      Alex Merry <alex.merry@kde.org>
+# Copyright 2014-2015 Alex Merry <alex.merry@kde.org>
 # Copyright 2013      Stephen Kelly <steveire@gmail.com>
 # Copyright 2012      David Faure <faure@kde.org>
 # Copyright 2007      Matthias Kretz <kretz@kde.org>
@@ -280,7 +280,18 @@ macro(_define_relative varname parent subdir docstring)
         set(_realpath "${_subdir}")
     endif()
 
-    if(${_oldstylename})
+    if(KDE_INSTALL_${varname})
+        # make sure the cache documentation is set correctly
+        get_property(_iscached CACHE KDE_INSTALL_${varname} PROPERTY VALUE SET)
+        if (_iscached)
+            # make sure the docs are still set if it was passed on the command line
+            set_property(CACHE KDE_INSTALL_${varname}
+                PROPERTY HELPSTRING "${docstring} (${_docpath})")
+            # make sure the type is correct if it was passed on the command line
+            set_property(CACHE KDE_INSTALL_${varname}
+                PROPERTY TYPE PATH)
+        endif()
+    elseif(${_oldstylename})
         if(NOT CMAKE_VERSION VERSION_LESS 3.0.0)
             message(DEPRECATION "${_oldstylename} is deprecated, use KDE_INSTALL_${varname} instead.")
         endif()
@@ -290,10 +301,6 @@ macro(_define_relative varname parent subdir docstring)
             CACHE PATH
                   "${docstring} (${_docpath})"
                   FORCE)
-        unset(${_oldstylename} CACHE)
-        if(_cmakename AND ${_cmakename})
-            unset(${_cmakename} CACHE)
-        endif()
     elseif(${_cmakename})
         if(_cmakename_is_deprecated AND NOT CMAKE_VERSION VERSION_LESS 3.0.0)
             message(DEPRECATION "${_cmakename} is deprecated, use KDE_INSTALL_${varname} instead.")
@@ -304,21 +311,12 @@ macro(_define_relative varname parent subdir docstring)
             CACHE PATH
                   "${docstring} (${_docpath})"
                   FORCE)
-        unset(${_cmakename} CACHE)
-    elseif(NOT KDE_INSTALL_${varname})
+    else()
+        # insert an empty value into the cache, indicating the default
+        # should be used (including compatibility vars above)
         set(KDE_INSTALL_${varname} ""
             CACHE PATH "${docstring} (${_docpath})")
         set(KDE_INSTALL_${varname} "${_realpath}")
-    else()
-        get_property(_iscached CACHE KDE_INSTALL_${varname} PROPERTY VALUE SET)
-        if (_iscached)
-            # make sure the docs are still set if it was passed on the command line
-            set_property(CACHE KDE_INSTALL_${varname}
-                PROPERTY HELPSTRING "${docstring} (${_docpath})")
-            # make sure the type is correct if it was passed on the command line
-            set_property(CACHE KDE_INSTALL_${varname}
-                PROPERTY TYPE PATH)
-        endif()
     endif()
 
     mark_as_advanced(KDE_INSTALL_${varname})
@@ -330,6 +328,10 @@ macro(_define_relative varname parent subdir docstring)
         set(KDE_INSTALL_FULL_${varname} "${KDE_INSTALL_${varname}}")
     endif()
 
+    # Override compatibility vars at runtime, even though we don't touch
+    # them in the cache; this way, we keep the variables in sync where
+    # KDEInstallDirs is included, but don't interfere with, say,
+    # GNUInstallDirs in a parallel part of the CMake tree.
     if(_cmakename)
         set(${_cmakename} "${KDE_INSTALL_${varname}}")
         set(CMAKE_INSTALL_FULL_${varname} "${KDE_INSTALL_FULL_${varname}}")