BUG: Alternative fix to bug #8423

The patch used to fix this bug used SystemTools::GetRealPath which works
only for existing files.  It broke the case of using the command
get_filename_component for a non-existing file.  Also, it changed
long-standing behavior in a possibly incompatible way even for existing
files.  This reverts the original fix and instead updates the
documentation to be consistent with the behavior.

Source/cmGetFilenameComponentCommand.cxx

@@ -91,8 +91,7 @@ bool cmGetFilenameComponentCommand
       }
 
     // Collapse the path to its simplest form.
-    filename = cmSystemTools::CollapseFullPath(filename.c_str());
-    result   = cmSystemTools::GetRealPath(filename.c_str());
+    result = cmSystemTools::CollapseFullPath(filename.c_str());
     }
   else 
     {

Source/cmGetFilenameComponentCommand.h

@@ -72,7 +72,7 @@ public:
       "                         [CACHE])\n"
       "Set VarName to be the path (PATH), file name (NAME), file "
       "extension (EXT), file name without extension (NAME_WE) of FileName, "
-      "or the full absolute (ABSOLUTE) file name without symlinks.  "
+      "or the full path (ABSOLUTE).  "
       "Note that the path is converted to Unix slashes format and has no "
       "trailing slashes. The longest file extension is always considered. "
       "If the optional CACHE argument is specified, the result variable is "

Tests/CMakeTests/CMakeLists.txt

@@ -14,7 +14,6 @@ AddCMakeTest(VariableWatch "")
 AddCMakeTest(Include "")
 AddCMakeTest(FindBase "")
 AddCMakeTest(Toolchain "")
-AddCMakeTest(GetFilenameComponentSymlinks "")
 
 SET(GetPrerequisites_PreArgs
   "-DCTEST_CONFIGURATION_TYPE:STRING=\\\${CTEST_CONFIGURATION_TYPE}"

Tests/CMakeTests/GetFilenameComponentSymlinksTest.cmake.in

@@ -1,43 +0,0 @@
-if(UNIX)
-    # file1 => file2 => file3 (real)
-
-    set(bindir ${CMAKE_CURRENT_BINARY_DIR})
-
-    file(WRITE ${bindir}/file3 "test file")
-    find_program(LN NAMES "ln")
-
-    if(LN)
-        # Create symlinks using "ln -s"
-        if(NOT EXISTS ${bindir}/file2)
-            execute_process(COMMAND ${LN} "-s" "${bindir}/file3" "${bindir}/file2")
-        endif()
-        if(NOT EXISTS ${bindir}/file1)
-            execute_process(COMMAND ${LN} "-s" "${bindir}/file2" "${bindir}/file1")
-        endif()
-
-        get_filename_component(file1 ${bindir}/file1 ABSOLUTE)
-        get_filename_component(file2 ${bindir}/file2 ABSOLUTE)
-        get_filename_component(file3 ${bindir}/file3 ABSOLUTE)
-
-        if(NOT file3 STREQUAL "${bindir}/file3")
-            message(FATAL_ERROR "CMake fails resolving absolute file file3")
-        endif()
-
-        if(NOT file2 STREQUAL "${bindir}/file3")
-            message(FATAL_ERROR "CMake fails resolving simple symlink")
-        endif()
-
-        if(NOT file1 STREQUAL "${bindir}/file3")
-            message(FATAL_ERROR "CMake fails resolving double symlink")
-        endif()
-
-        # cleanup
-        file(REMOVE ${bindir}/file1)
-        file(REMOVE ${bindir}/file2)
-        file(REMOVE ${bindir}/file3)
-        if(EXISTS file1 OR EXISTS file2 OR EXISTS file3)
-           message(FATAL_ERROR "removal of file1, file2, or file3 failed")
-        endif()
-
-    endif(LN)
-endif()