ENH: Add get_filename_component(... REALPATH)

This patch from Philip Lowman creates a REALPATH mode in the
get_filename_component command.  It is like ABSOLUTE, but will also
resolve symlinks (which ABSOLUTE once did but was broken long ago).
See issue #8423.

2 files changed, 58 insertions, 0 deletions

diff --git a/Tests/CMakeTests/CMakeLists.txt b/Tests/CMakeTests/CMakeLists.txt
index 9f91abc..9e3c3e7 100644
--- a/Tests/CMakeTests/CMakeLists.txt
+++ b/Tests/CMakeTests/CMakeLists.txt
@@ -14,6 +14,7 @@ AddCMakeTest(VariableWatch "")
 AddCMakeTest(Include "")
 AddCMakeTest(FindBase "")
 AddCMakeTest(Toolchain "")
+AddCMakeTest(GetFilenameComponentRealpath "")
 
 SET(GetPrerequisites_PreArgs
   "-DCTEST_CONFIGURATION_TYPE:STRING=\\\${CTEST_CONFIGURATION_TYPE}"
diff --git a/Tests/CMakeTests/GetFilenameComponentRealpathTest.cmake.in b/Tests/CMakeTests/GetFilenameComponentRealpathTest.cmake.in
new file mode 100644
index 0000000..c795512
--- /dev/null
+++ b/Tests/CMakeTests/GetFilenameComponentRealpathTest.cmake.in
@@ -0,0 +1,57 @@
+set(bindir ${CMAKE_CURRENT_BINARY_DIR})
+
+#
+# Test nonexistent REALPATH & ABSOLUTE resolution
+#
+get_filename_component(nonexistent1 ${bindir}/THIS_IS_A_NONEXISTENT_FILE REALPATH)
+get_filename_component(nonexistent2 ${bindir}/THIS_IS_A_NONEXISTENT_FILE ABSOLUTE)
+if(NOT nonexistent1 STREQUAL "${bindir}/THIS_IS_A_NONEXISTENT_FILE")
+    message(FATAL_ERROR "REALPATH is not preserving nonexistent files")
+endif()
+if(NOT nonexistent2 STREQUAL "${bindir}/THIS_IS_A_NONEXISTENT_FILE")
+    message(FATAL_ERROR "ABSOLUTE is not preserving nonexistent files")
+endif()
+
+#
+# Test symbolic link resolution
+#
+if(UNIX)
+    # file1 => file2 => file3 (real)
+    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 REALPATH)
+        get_filename_component(file2 ${bindir}/file2 REALPATH)
+        get_filename_component(file3 ${bindir}/file3 REALPATH)
+
+        if(NOT file3 STREQUAL "${bindir}/file3")
+            message(FATAL_ERROR "CMake fails resolving REALPATH 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)
+        if(EXISTS file1 OR EXISTS file2)
+           message(FATAL_ERROR "removal of file1 or file2 failed")
+        endif()
+    endif(LN)
+
+    file(REMOVE ${bindir}/file3)
+endif()