install(DIRECTORY): Revert "Add EXCLUDE_EMPTY_DIRECTORIES option"

Revert commit b70ef48b27 (install(DIRECTORY): Add
EXCLUDE_EMPTY_DIRECTORIES option, 2025-04-20, v4.1.0-rc1~212^2).
The implementation had at least two problems:

* It did not exclude the top-level directory if empty.
* It did not exclude non-empty directories whose contents are
  all filtered out.

Revert the feature pending a revised implementation.

Issue: #19189
Closes: #27092

Help/command/install.rst

@@ -648,7 +648,6 @@ Signatures
             [USE_SOURCE_PERMISSIONS] [OPTIONAL] [MESSAGE_NEVER]
             [CONFIGURATIONS <config>...]
             [COMPONENT <component>] [EXCLUDE_FROM_ALL]
-            [EXCLUDE_EMPTY_DIRECTORIES]
             [FILES_MATCHING]
             [<match-rule> <match-option>...]...
             )
@@ -751,13 +750,6 @@ Signatures
 
     Disable file installation status output.
 
-  ``EXCLUDE_EMPTY_DIRECTORIES``
-    .. versionadded:: 4.1
-
-    Exclude empty directories from installation.  A directory is
-    considered empty if it contains no files, no symbolic links,
-    and no non-empty subdirectories.
-
   ``FILES_MATCHING``
     This option may be given before the first ``<match-rule>`` to
     disable installation of files (but not directories) not matched

Help/release/4.1.rst

@@ -71,10 +71,6 @@ Commands
   ``POPULATE`` subcommands for interfacing CMake targets with pkg-config based
   dependencies.
 
-* The :command:`install(DIRECTORY)` command gained a new
-  ``EXCLUDE_EMPTY_DIRECTORIES`` option to skip installation
-  of empty directories.
-
 * The :command:`project` command now has experimental support for the
   ``COMPAT_VERSION`` keyword, gated by
   ``CMAKE_EXPERIMENTAL_EXPORT_PACKAGE_INFO``.

Source/cmFileCopier.cxx

@@ -25,10 +25,6 @@
 
 #include <cstring>
 #include <sstream>
-#include <utility>
-
-#include <cm/string_view>
-#include <cmext/string_view>
 
 using namespace cmFSPermissions;
 
@@ -298,13 +294,6 @@ bool cmFileCopier::CheckKeyword(std::string const& arg)
       this->Doing = DoingNone;
       this->MatchlessFiles = false;
     }
-  } else if (arg == "EXCLUDE_EMPTY_DIRECTORIES") {
-    if (this->CurrentMatchRule) {
-      this->NotAfterMatch(arg);
-    } else {
-      this->Doing = DoingNone;
-      this->ExcludeEmptyDirectories = true;
-    }
   } else {
     return false;
   }
@@ -658,29 +647,6 @@ bool cmFileCopier::InstallFile(std::string const& fromFile,
   return this->SetPermissions(toFile, permissions);
 }
 
-static bool IsEmptyDirectory(std::string const& path,
-                             std::unordered_map<std::string, bool>& cache)
-{
-  auto i = cache.find(path);
-  if (i == cache.end()) {
-    bool isEmpty = (!cmSystemTools::FileIsSymlink(path) &&
-                    cmSystemTools::FileIsDirectory(path));
-    if (isEmpty) {
-      cmsys::Directory d;
-      d.Load(path);
-      unsigned long numFiles = d.GetNumberOfFiles();
-      for (unsigned long fi = 0; isEmpty && fi < numFiles; ++fi) {
-        std::string const& name = d.GetFileName(fi);
-        if (name != "."_s && name != ".."_s) {
-          isEmpty = IsEmptyDirectory(d.GetFilePath(fi), cache);
-        }
-      }
-    }
-    i = cache.emplace(path, isEmpty).first;
-  }
-  return i->second;
-}
-
 bool cmFileCopier::InstallDirectory(std::string const& source,
                                     std::string const& destination,
                                     MatchProperties match_properties)
@@ -753,11 +719,6 @@ bool cmFileCopier::InstallDirectory(std::string const& source,
           strcmp(dir.GetFile(fileNum), "..") == 0)) {
       std::string fromPath = cmStrCat(source, '/', dir.GetFile(fileNum));
       std::string toPath = cmStrCat(destination, '/', dir.GetFile(fileNum));
-      if (this->ExcludeEmptyDirectories &&
-          IsEmptyDirectory(fromPath, this->DirEmptyCache)) {
-        continue;
-      }
-
       if (!this->Install(fromPath, toPath)) {
         return false;
       }

Source/cmFileCopier.h

@@ -5,7 +5,6 @@
 #include "cmConfigure.h" // IWYU pragma: keep
 
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 #include "cmsys/RegularExpression.hxx"
@@ -31,7 +30,6 @@ protected:
   char const* Name;
   bool Always = false;
   cmFileTimeCache FileTimes;
-  std::unordered_map<std::string, bool> DirEmptyCache;
 
   // Whether to install a file not matching any expression.
   bool MatchlessFiles = true;
@@ -91,7 +89,6 @@ protected:
   bool UseGivenPermissionsFile = false;
   bool UseGivenPermissionsDir = false;
   bool UseSourcePermissions = true;
-  bool ExcludeEmptyDirectories = false;
   bool FollowSymlinkChain = false;
   std::string Destination;
   std::string FilesFromDir;

Source/cmInstallCommand.cxx

@@ -1787,14 +1787,6 @@ bool HandleDirectoryMode(std::vector<std::string> const& args,
       }
       exclude_from_all = true;
       doing = DoingNone;
-    } else if (args[i] == "EXCLUDE_EMPTY_DIRECTORIES") {
-      if (in_match_mode) {
-        status.SetError(cmStrCat(args[0], " does not allow \"", args[i],
-                                 "\" after PATTERN or REGEX."));
-        return false;
-      }
-      literal_args += " EXCLUDE_EMPTY_DIRECTORIES";
-      doing = DoingNone;
     } else if (doing == DoingDirs) {
       // Convert this directory to a full path.
       std::string dir = args[i];

Tests/RunCMake/install/DIRECTORY-EXCLUDE_EMPTY_DIRECTORIES-check.cmake

@@ -1,30 +0,0 @@
-file(REMOVE_RECURSE ${RunCMake_TEST_BINARY_DIR}/prefix)
-
-execute_process(COMMAND ${CMAKE_COMMAND} -P ${RunCMake_TEST_BINARY_DIR}/cmake_install.cmake
-  OUTPUT_VARIABLE out ERROR_VARIABLE err)
-
-set(f ${RunCMake_TEST_BINARY_DIR}/prefix/dir_to_install/empty.txt)
-if(NOT EXISTS "${f}")
-  string(APPEND RunCMake_TEST_FAILED
-    "File was not installed:\n  ${f}\n")
-endif()
-
-set(empty_folder ${RunCMake_TEST_BINARY_DIR}/prefix/dir_to_install/empty_folder)
-if(EXISTS "${empty_folder}")
-  string(APPEND RunCMake_TEST_FAILED
-    "empty_folder should not have be installed:\n  ${empty_folder}\n")
-endif()
-
-if(UNIX)
-  set(folder_with_symlink ${RunCMake_TEST_BINARY_DIR}/prefix/dir_to_install/folder_with_symlink)
-  if(NOT EXISTS "${folder_with_symlink}")
-    string(APPEND RunCMake_TEST_FAILED
-      "folder_with_symlink was not installed:\n  ${folder_with_symlink}\n")
-  endif()
-
-  set(symlink_to_empty_txt ${RunCMake_TEST_BINARY_DIR}/prefix/dir_to_install/folder_with_symlink/symlink_to_empty.txt)
-  if(NOT EXISTS "${symlink_to_empty_txt}")
-    string(APPEND RunCMake_TEST_FAILED
-      "symlink_to_empty.txt was not installed:\n  ${symlink_to_empty_txt}\n")
-  endif()
-endif()

Tests/RunCMake/install/DIRECTORY-EXCLUDE_EMPTY_DIRECTORIES.cmake

@@ -1,27 +0,0 @@
-set(CMAKE_INSTALL_MESSAGE "ALWAYS")
-set(CMAKE_INSTALL_PREFIX "${CMAKE_BINARY_DIR}/prefix")
-
-set(DIR_TO_INSTALL "${CMAKE_BINARY_DIR}/dir_to_install")
-file(MAKE_DIRECTORY ${DIR_TO_INSTALL})
-
-file(TOUCH ${DIR_TO_INSTALL}/empty.txt)
-
-# make an empty folder
-file(MAKE_DIRECTORY ${DIR_TO_INSTALL}/empty_folder)
-# make empty subfolders under the empty folder
-file(MAKE_DIRECTORY ${DIR_TO_INSTALL}/empty_folder/empty_subfolder1)
-file(MAKE_DIRECTORY ${DIR_TO_INSTALL}/empty_folder/empty_subfolder2)
-
-if(UNIX)
-  # make an folder with a symlink
-  file(MAKE_DIRECTORY ${DIR_TO_INSTALL}/folder_with_symlink)
-  file(CREATE_LINK ${DIR_TO_INSTALL}/empty.txt
-    ${DIR_TO_INSTALL}/folder_with_symlink/symlink_to_empty.txt
-    SYMBOLIC
-  )
-endif()
-
-install(DIRECTORY ${DIR_TO_INSTALL}
-    DESTINATION ${CMAKE_INSTALL_PREFIX}
-    EXCLUDE_EMPTY_DIRECTORIES
-)

Tests/RunCMake/install/DIRECTORY-PATTERN-EXCLUDE_EMPTY_DIRECTORIES-result.txt

@@ -1 +0,0 @@
-1

Tests/RunCMake/install/DIRECTORY-PATTERN-EXCLUDE_EMPTY_DIRECTORIES-stderr.txt

@@ -1,5 +0,0 @@
-CMake Error at DIRECTORY-PATTERN-EXCLUDE_EMPTY_DIRECTORIES.cmake:[0-9]+ \(install\):
-  install DIRECTORY does not allow "EXCLUDE_EMPTY_DIRECTORIES" after PATTERN
-  or REGEX\.
-Call Stack \(most recent call first\):
-  CMakeLists\.txt:[0-9]+ \(include\)

Tests/RunCMake/install/DIRECTORY-PATTERN-EXCLUDE_EMPTY_DIRECTORIES.cmake

@@ -1 +0,0 @@
-install(DIRECTORY src DESTINATION src PATTERN *.txt EXCLUDE_EMPTY_DIRECTORIES)

Tests/RunCMake/install/RunCMakeTest.cmake

@@ -73,8 +73,6 @@ run_cmake(DIRECTORY-MESSAGE_NEVER)
 run_cmake(DIRECTORY-PATTERN-MESSAGE_NEVER)
 run_cmake(DIRECTORY-message)
 run_cmake(DIRECTORY-message-lazy)
-run_cmake(DIRECTORY-EXCLUDE_EMPTY_DIRECTORIES)
-run_cmake(DIRECTORY-PATTERN-EXCLUDE_EMPTY_DIRECTORIES)
 run_cmake(SkipInstallRulesWarning)
 run_cmake(SkipInstallRulesNoWarning1)
 run_cmake(SkipInstallRulesNoWarning2)