Rebuild project targets when needed

This is initial solution to bring all project targets to updated state
when PHP is not found on the system, while still enabling development
with the built PHP itself.

Author: petk

cmake/cmake/Bootstrap.cmake

@@ -46,6 +46,11 @@ include(cmake/Configuration.cmake)
 # Check requirements.
 include(cmake/Requirements.cmake)
 
+# Rebuild all targets when needed.
+if(NOT PHPSystem_EXECUTABLE)
+  include(PHP/Rebuild)
+endif()
+
 message("
 Running system checks
 ---------------------

cmake/cmake/modules/PHP/PositionIndependentCode.cmake

@@ -4,6 +4,8 @@ Check whether to enable the `POSITION_INDEPENDENT_CODE` or not.
 https://cmake.org/cmake/help/latest/variable/CMAKE_POSITION_INDEPENDENT_CODE.html
 #]=============================================================================]
 
+include_guard(GLOBAL)
+
 if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND CMAKE_SIZEOF_VOID_P EQUAL 4)
   # On 32-bit *nix (Linux and FreeBSD at least) when using Clang, the PIC is
   # required.

cmake/cmake/modules/PHP/Rebuild.cmake

@@ -0,0 +1,64 @@
+#[=============================================================================[
+Rebuild all project targets.
+
+When PHP is not found on the system, PHP generates some files during development
+using the php_cli target itself, which can bring cyclic dependencies among
+targets if custom commands would depend on the php_cli target. Although not a
+good practice, this helps bringing all targets to updated state.
+#]=============================================================================]
+
+include_guard(GLOBAL)
+
+# Store a list of all targets inside the given <dir> into the <result> variable.
+function(_php_get_all_targets result dir)
+  get_property(targets DIRECTORY ${dir} PROPERTY BUILDSYSTEM_TARGETS)
+  get_property(subdirs DIRECTORY ${dir} PROPERTY SUBDIRECTORIES)
+
+  foreach(subdir ${subdirs})
+    cmake_language(CALL ${CMAKE_CURRENT_FUNCTION} subdirTargets ${subdir})
+    list(APPEND targets ${subdirTargets})
+  endforeach()
+
+  set(${result} ${targets} PARENT_SCOPE)
+endfunction()
+
+# Ensure all project targets are rebuilt as needed.
+function(_php_rebuild)
+  _php_get_all_targets(targets ${CMAKE_CURRENT_SOURCE_DIR})
+  list(REMOVE_ITEM targets "php_rebuild")
+
+  add_custom_command(
+    OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/php_rebuild.timestamp
+    COMMAND
+      ${CMAKE_COMMAND}
+        -E cmake_echo_color --magenta --bold "       Updating targets"
+    COMMAND
+      ${CMAKE_COMMAND}
+        -E touch ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/php_rebuild.timestamp
+    COMMAND
+      ${CMAKE_COMMAND}
+        --build . --target php_rebuild -j
+    WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+    DEPENDS ${targets}
+  )
+
+  add_custom_target(
+    php_update_targets ALL
+    DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/php_rebuild.timestamp
+  )
+
+  add_custom_target(
+    php_rebuild
+    COMMAND
+      ${CMAKE_COMMAND}
+        -E rm -f ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/php_rebuild.timestamp
+    DEPENDS ${targets}
+  )
+endfunction()
+
+# Run at the end of the configuration.
+cmake_language(
+  DEFER
+    DIRECTORY ${PROJECT_SOURCE_DIR}
+  CALL _php_rebuild
+)